Cardiac artifacts appear as periodic waves that are time-locked to the heartbeat as recorded by ECG. They include electrical artifacts seen as QRS complexes and mechanical artifacts seen as pulse waves. Electrode artifacts occur due to poor electrode contact or lead movement and appear as irregular waves of varying morphology and amplitude. External device artifacts are caused by electrical or mechanical devices and may appear as 50/60Hz noise, spike-like waves from IV drips, or irregular high amplitude waves from electrical motors. Artifacts must be distinguished from physiological activity and epileptiform discharges based on characteristics like distribution, morphology, and periodicity to avoid misinterpretation.
EEG artifacts can arise from various physiological and extraphysiological sources other than brain activity. Physiological artifacts originate from the patient's own generator sources like eye movements, muscle activity, movement, and cardiac activity. Extraphysiological artifacts are externally generated, such as from medical devices, electrical equipment, or the environment. Common EEG artifacts include cardiac artifacts like ECG signals, ballistocardiographic artifacts from head or body movement, pacemaker signals, and pulse artifacts. Electrode artifacts can be transient pops or low frequency rhythms across electrodes from poor contact or movement. External artifacts include 50/60 Hz ambient noise, intravenous drips, and signals from devices like pumps and ventilators. Muscle and ocular artifacts
This document discusses different types of artifacts that can appear on an EEG, including how to identify and eliminate them. It separates artifacts into physiological artifacts originating from the patient's body (e.g. eye movements, muscle activity), and extraphysiological artifacts from external sources (e.g. electrodes, equipment, environment). Specific artifact types like blinks, lateral eye movements, muscle activity are described. Guidelines provided on how to reduce artifacts include closing the eyes, relaxing muscles, ensuring good electrode contact, and shielding from environmental interference.
This document discusses various types of EEG artifacts including physiological artifacts generated by the body and extraphysiological artifacts from external equipment or environment. It describes common artifacts like cardiac, electrode, eye blink, muscle activity and their characteristic appearances on EEG. The key is to ensure good preparation, electrode placement and monitoring for artifacts during EEG recording to obtain clean data for accurate interpretation.
This presentation looks at abnormal EEG patterns with examples for each. Benign variants, artifacts and focal ictal patterns are not part of this presentation.
The document discusses the mu rhythm, which is a central rhythm seen on EEG with an alpha frequency band of 8-10 Hz. It has an arciform configuration and occurs in less than 5% of children under age 4 and 18-20% of children ages 8-16. The mu rhythm is not blocked by eye opening but is blocked by touch, limb movement, or thought of movement. It is usually asymmetric and independent between hemispheres. The mu rhythm is believed to originate from the sensorimotor cortex at rest and can be prominent in patients with skull defects.
This presentation reviews the common artifacts in EEG, their identification and rectification. Examples of various artifacts are provided in the presentation.
EEG artefacts arise from unwanted electrical activity from sources other than the brain, such as eye movements, muscle activity, and environmental noise. Identifying artefacts can be challenging as some resemble brain activity. Methods for removing artefacts include filtering, regression-based approaches, and independent component analysis, which transforms scalp channel data into spatially independent sources that may represent brain or non-brain activity. Careful inspection of component properties like scalp maps, time courses, and spectra is needed to classify them as representing brain activity or artefacts.
- The EEG records electrical activity from the cerebral cortex which is amplified over 10 million times to be visible. It detects action potentials and post-synaptic potentials from neurons.
- Electrodes are placed on standardized locations on the scalp according to the 10-20 or 10-10 systems to allow comparison across studies. Recordings can be bipolar between adjacent electrodes or referential against a common electrode.
- Activity is recorded through amplifiers and can be displayed through different montages optimized for localization or overall brain activity. Calibration ensures consistent sensitivity and filtering removes unwanted interference.
EEG artifacts can arise from various physiological and extraphysiological sources other than brain activity. Physiological artifacts originate from the patient's own generator sources like eye movements, muscle activity, movement, and cardiac activity. Extraphysiological artifacts are externally generated, such as from medical devices, electrical equipment, or the environment. Common EEG artifacts include cardiac artifacts like ECG signals, ballistocardiographic artifacts from head or body movement, pacemaker signals, and pulse artifacts. Electrode artifacts can be transient pops or low frequency rhythms across electrodes from poor contact or movement. External artifacts include 50/60 Hz ambient noise, intravenous drips, and signals from devices like pumps and ventilators. Muscle and ocular artifacts
This document discusses different types of artifacts that can appear on an EEG, including how to identify and eliminate them. It separates artifacts into physiological artifacts originating from the patient's body (e.g. eye movements, muscle activity), and extraphysiological artifacts from external sources (e.g. electrodes, equipment, environment). Specific artifact types like blinks, lateral eye movements, muscle activity are described. Guidelines provided on how to reduce artifacts include closing the eyes, relaxing muscles, ensuring good electrode contact, and shielding from environmental interference.
This document discusses various types of EEG artifacts including physiological artifacts generated by the body and extraphysiological artifacts from external equipment or environment. It describes common artifacts like cardiac, electrode, eye blink, muscle activity and their characteristic appearances on EEG. The key is to ensure good preparation, electrode placement and monitoring for artifacts during EEG recording to obtain clean data for accurate interpretation.
This presentation looks at abnormal EEG patterns with examples for each. Benign variants, artifacts and focal ictal patterns are not part of this presentation.
The document discusses the mu rhythm, which is a central rhythm seen on EEG with an alpha frequency band of 8-10 Hz. It has an arciform configuration and occurs in less than 5% of children under age 4 and 18-20% of children ages 8-16. The mu rhythm is not blocked by eye opening but is blocked by touch, limb movement, or thought of movement. It is usually asymmetric and independent between hemispheres. The mu rhythm is believed to originate from the sensorimotor cortex at rest and can be prominent in patients with skull defects.
This presentation reviews the common artifacts in EEG, their identification and rectification. Examples of various artifacts are provided in the presentation.
EEG artefacts arise from unwanted electrical activity from sources other than the brain, such as eye movements, muscle activity, and environmental noise. Identifying artefacts can be challenging as some resemble brain activity. Methods for removing artefacts include filtering, regression-based approaches, and independent component analysis, which transforms scalp channel data into spatially independent sources that may represent brain or non-brain activity. Careful inspection of component properties like scalp maps, time courses, and spectra is needed to classify them as representing brain activity or artefacts.
- The EEG records electrical activity from the cerebral cortex which is amplified over 10 million times to be visible. It detects action potentials and post-synaptic potentials from neurons.
- Electrodes are placed on standardized locations on the scalp according to the 10-20 or 10-10 systems to allow comparison across studies. Recordings can be bipolar between adjacent electrodes or referential against a common electrode.
- Activity is recorded through amplifiers and can be displayed through different montages optimized for localization or overall brain activity. Calibration ensures consistent sensitivity and filtering removes unwanted interference.
This document describes several benign EEG variants that can have an epileptiform appearance but are not epileptogenic. It discusses characteristics of alpha variants, mu rhythm, lambda waves, rhythmic mid-temporal theta discharges, wicket spikes, subclinical rhythmic electroencephalographic discharges of adults, phantom spike-wave discharges, and small sharp spikes. These benign variants can occur during drowsiness and light sleep and are seen in specific electrode sites, with features like attenuation with eye opening or movement in the case of mu rhythm. Accurate identification requires training to distinguish them from true epileptiform discharges.
This presentation discusses the basic principles governing EEG Rhythm Generation, and discusses the various circuits that generate and maintain cerebral oscillations.
This document discusses different types of artifacts that can appear in EEG recordings. It divides artifacts into physiological artifacts, caused by body movements or electrical activity, and non-physiological artifacts, caused by external electrical interference or equipment issues. Specific artifacts covered include eye blinks and movements, muscle activity, sweat, ECG interference, ventilator and pulse artifacts, electrical interference, and electrode and lead movement issues. Proper identification of artifacts is important for interpreting EEG recordings.
1. The document discusses various abnormal EEG patterns including slowing, spikes, sharp waves, and other abnormalities. It provides details on types of slowing such as focal, regional, and generalized slowing.
2. Different types of spikes and sharp waves are defined including their durations. Both focal and generalized spike/sharp wave abnormalities are described.
3. Specific abnormal EEG patterns are explained in detail such as frontal intermittent rhythmic delta activity (FIRDA), polymorphic delta activity (PDA), and benign focal epilepsies of childhood including rolandic and occipital epilepsy. Causes and differentiation of these patterns are provided.
This lecture is all about the recognition of an abnormal EEG, its characteristics, its appearance and all about how to differentiate the abnormal activity with normal EEG background.
This presentation looks at EEG signal generation, pyramidal cells, recording of EEG, source localisation, polarity, analysis of dipole, derivations, montages,
Triphasic waves are abnormal EEG waveforms seen in association with metabolic encephalopathies and structural brain lesions. They were first described in 1950 in a patient with hepatic encephalopathy. Triphasic waves result from dysfunction of the oscillatory system between the cortex and thalamus. They have a characteristic three-phase morphology visible on EEG. Triphasic waves can be typical or atypical depending on their characteristics and underlying etiology. Typical triphasic waves are seen in metabolic encephalopathies while atypical may indicate an epileptogenic condition. The presence of triphasic waves provides guidance for treatment of the underlying condition.
Normal EEG patterns, frequencies, as well as patterns that may simulate diseaseRahul Kumar
This presentation discusses the vast range of traces that show the variations in normal EEG patterns, as well as discussing the frequency and amplitudes of various normal waveforms.
The document discusses normal EEG patterns in various age groups from neonatal to adulthood. In neonates, the EEG pattern depends on gestational age and includes discontinuity in premature infants. In infancy and early childhood, the posterior dominant rhythm increases in frequency and reactivity emerges. By adolescence, the EEG begins to resemble the adult pattern with less delta activity. The normal adult EEG shows an alpha rhythm over the occipital lobe that attenuates with eye opening. Theta is only present in sleep while delta is never seen in awake adults.
This document discusses several normal EEG patterns seen in sleep, including:
1) Positive occipital sharp transients of sleep (POSTs), which appear as sharp waves over the occipital regions during light sleep and stage 2 sleep in most healthy adults and children over 3 years old.
2) Posterior slow-wave transients associated with eye movements, seen as slow waves over the occipital regions following eye blinks or movements in children aged 6 months to 10 years.
3) Occipital slow transients or "cone waves", seen as high amplitude slow waves over the occipital regions during transitions from light to deep sleep in infants and children up to age 5.
EEG - Montages, Equipment and Basic PhysicsRahul Kumar
This presentation discusses the 10-20 system of electrode placement, with its modifications. Also discussed are the Equipment Specifications, basic Physics and sources of interference
Periodic Lateralized Epileptiform Discharges (PLEDs) are repeating waveforms seen on EEG that occur at regular intervals and are localized to one hemisphere. They are commonly seen after acute cortical injuries like stroke and infections. PLEDs are classified based on their pattern and presence of additional rhythmic discharges. They indicate unstable brain physiology resulting from seizures, injury or metabolic disturbances. While not strictly ictal, PLEDs are associated with increased risk of clinical seizures. Prognosis depends on the underlying cause, with acute severe strokes having the worst outcomes. Treatment involves antiepileptic drugs mainly if clinical seizures are present.
This document discusses posterior slow waves of youth, also known as youth waves or polyphasic waves. It provides details on the following:
- These waves are high-voltage theta or delta waves seen in children aged 8-14 years that are accompanied by the alpha rhythm.
- They typically appear unilaterally or bilaterally and are attenuated with eye opening.
- Examples are shown from EEGs of children ages 9-10 years exhibiting occipital slow waves mixing with and interrupting the alpha rhythm.
- Characteristics including incidence, voltage ratio, persistence with eye opening, and symmetry are discussed. An example shows intermittent right occipital delta slowing in an 8-year-old
Artifacts in EEG - Recognition and differentiationRahul Kumar
This Presentation discusses the variously commonly seen artifacts in EEG, and how to recognize them. In EEG interpretation, it is often more important to identify an artifact than to identify true pathology. Once all the artifacts are ruled out, one is sure that what one is dealing with represents disease/abnormality
1) The document describes several benign EEG variants that can occur but are not associated with epilepsy. These include wicket waves, benign sporadic sleep spikes, 6 per second spike-waves, 14 & 6 Hz positive spikes, and more.
2) The variants are described in terms of their frequency, location, morphology, when they typically occur, and other characteristics. For example, wicket waves occur in the alpha frequency range and are seen unilaterally in the temporal region.
3) Many of the variants are considered normal variants seen in relaxed wakefulness, drowsiness, or different stages of sleep. They are commonly seen in different age groups but are not clinically significant or associated with epilepsy.
This document provides an overview of normal EEG patterns in adults. It begins with a brief history of EEG and then describes the basic electrical activity generated by the brain and how EEG recordings work. It outlines the normal frequency bands seen in EEG - delta, theta, alpha, beta and gamma. Specific normal EEG patterns like the alpha rhythm, vertex waves, sleep spindles and K-complexes are described. It also discusses benign variants and activation procedures. In summary, the document serves as a reference for the typical EEG patterns seen in healthy, awake and sleeping adults.
ECOG involves directly recording cortical electrical activity from the surface of the brain. It is used to localize epileptogenic regions and predict surgical outcomes. There are two main types - intraoperative ECOG during surgery and extraoperative ECOG for longer monitoring. Subdural grids and strips can be placed on the brain surface or depth electrodes can access deeper structures. ECOG is performed by placing electrode arrays on the exposed brain during a craniotomy procedure. It provides valuable data to identify seizure foci but also carries risks like infection if implanted for longer periods.
EEG is used to record the electrical activity of the brain. It uses electrodes placed on the scalp that are smaller than those used in ECGs. EEG can be used to diagnose neurological disorders like epilepsy. There are different types of brain waves like delta, theta, alpha, beta, and gamma waves that are defined by their frequency ranges and locations in the brain. Evoked potentials involve stimulating specific sensory pathways and measuring the electrical response in certain brain areas to help diagnose conditions.
This document discusses artifacts and normal variants that may appear on EEG recordings. It describes various types of artifacts that can originate from patient physiology like eye movements, muscle activity, and heartbeats. It also discusses artifacts from external interference and equipment issues. Normal variants are described like alpha rhythm, sleep transients, and frontal rhythms seen in drowsiness that should not be mistaken for epileptiform activity. The document provides details on identifying features of each artifact and variant to differentiate them from cerebral abnormalities.
EEG variants, are always to be recognized while interpreting the EEG one must be aware of these. Major and most common EEG is variants are discussed in the stated presentation.
Syed Irshad Murtaza.
Este documento describe la electroencefalografía (EEG), un examen que registra la actividad eléctrica del cerebro. Explica cómo se colocan los electrodos en la cabeza siguiendo el sistema 10-20 internacional y cómo se amplifican, filtran y registran las señales cerebrales. Además, describe las diferentes ondas cerebrales como delta, theta, alfa y beta según su frecuencia e implicaciones funcionales y clínicas.
This document describes several benign EEG variants that can have an epileptiform appearance but are not epileptogenic. It discusses characteristics of alpha variants, mu rhythm, lambda waves, rhythmic mid-temporal theta discharges, wicket spikes, subclinical rhythmic electroencephalographic discharges of adults, phantom spike-wave discharges, and small sharp spikes. These benign variants can occur during drowsiness and light sleep and are seen in specific electrode sites, with features like attenuation with eye opening or movement in the case of mu rhythm. Accurate identification requires training to distinguish them from true epileptiform discharges.
This presentation discusses the basic principles governing EEG Rhythm Generation, and discusses the various circuits that generate and maintain cerebral oscillations.
This document discusses different types of artifacts that can appear in EEG recordings. It divides artifacts into physiological artifacts, caused by body movements or electrical activity, and non-physiological artifacts, caused by external electrical interference or equipment issues. Specific artifacts covered include eye blinks and movements, muscle activity, sweat, ECG interference, ventilator and pulse artifacts, electrical interference, and electrode and lead movement issues. Proper identification of artifacts is important for interpreting EEG recordings.
1. The document discusses various abnormal EEG patterns including slowing, spikes, sharp waves, and other abnormalities. It provides details on types of slowing such as focal, regional, and generalized slowing.
2. Different types of spikes and sharp waves are defined including their durations. Both focal and generalized spike/sharp wave abnormalities are described.
3. Specific abnormal EEG patterns are explained in detail such as frontal intermittent rhythmic delta activity (FIRDA), polymorphic delta activity (PDA), and benign focal epilepsies of childhood including rolandic and occipital epilepsy. Causes and differentiation of these patterns are provided.
This lecture is all about the recognition of an abnormal EEG, its characteristics, its appearance and all about how to differentiate the abnormal activity with normal EEG background.
This presentation looks at EEG signal generation, pyramidal cells, recording of EEG, source localisation, polarity, analysis of dipole, derivations, montages,
Triphasic waves are abnormal EEG waveforms seen in association with metabolic encephalopathies and structural brain lesions. They were first described in 1950 in a patient with hepatic encephalopathy. Triphasic waves result from dysfunction of the oscillatory system between the cortex and thalamus. They have a characteristic three-phase morphology visible on EEG. Triphasic waves can be typical or atypical depending on their characteristics and underlying etiology. Typical triphasic waves are seen in metabolic encephalopathies while atypical may indicate an epileptogenic condition. The presence of triphasic waves provides guidance for treatment of the underlying condition.
Normal EEG patterns, frequencies, as well as patterns that may simulate diseaseRahul Kumar
This presentation discusses the vast range of traces that show the variations in normal EEG patterns, as well as discussing the frequency and amplitudes of various normal waveforms.
The document discusses normal EEG patterns in various age groups from neonatal to adulthood. In neonates, the EEG pattern depends on gestational age and includes discontinuity in premature infants. In infancy and early childhood, the posterior dominant rhythm increases in frequency and reactivity emerges. By adolescence, the EEG begins to resemble the adult pattern with less delta activity. The normal adult EEG shows an alpha rhythm over the occipital lobe that attenuates with eye opening. Theta is only present in sleep while delta is never seen in awake adults.
This document discusses several normal EEG patterns seen in sleep, including:
1) Positive occipital sharp transients of sleep (POSTs), which appear as sharp waves over the occipital regions during light sleep and stage 2 sleep in most healthy adults and children over 3 years old.
2) Posterior slow-wave transients associated with eye movements, seen as slow waves over the occipital regions following eye blinks or movements in children aged 6 months to 10 years.
3) Occipital slow transients or "cone waves", seen as high amplitude slow waves over the occipital regions during transitions from light to deep sleep in infants and children up to age 5.
EEG - Montages, Equipment and Basic PhysicsRahul Kumar
This presentation discusses the 10-20 system of electrode placement, with its modifications. Also discussed are the Equipment Specifications, basic Physics and sources of interference
Periodic Lateralized Epileptiform Discharges (PLEDs) are repeating waveforms seen on EEG that occur at regular intervals and are localized to one hemisphere. They are commonly seen after acute cortical injuries like stroke and infections. PLEDs are classified based on their pattern and presence of additional rhythmic discharges. They indicate unstable brain physiology resulting from seizures, injury or metabolic disturbances. While not strictly ictal, PLEDs are associated with increased risk of clinical seizures. Prognosis depends on the underlying cause, with acute severe strokes having the worst outcomes. Treatment involves antiepileptic drugs mainly if clinical seizures are present.
This document discusses posterior slow waves of youth, also known as youth waves or polyphasic waves. It provides details on the following:
- These waves are high-voltage theta or delta waves seen in children aged 8-14 years that are accompanied by the alpha rhythm.
- They typically appear unilaterally or bilaterally and are attenuated with eye opening.
- Examples are shown from EEGs of children ages 9-10 years exhibiting occipital slow waves mixing with and interrupting the alpha rhythm.
- Characteristics including incidence, voltage ratio, persistence with eye opening, and symmetry are discussed. An example shows intermittent right occipital delta slowing in an 8-year-old
Artifacts in EEG - Recognition and differentiationRahul Kumar
This Presentation discusses the variously commonly seen artifacts in EEG, and how to recognize them. In EEG interpretation, it is often more important to identify an artifact than to identify true pathology. Once all the artifacts are ruled out, one is sure that what one is dealing with represents disease/abnormality
1) The document describes several benign EEG variants that can occur but are not associated with epilepsy. These include wicket waves, benign sporadic sleep spikes, 6 per second spike-waves, 14 & 6 Hz positive spikes, and more.
2) The variants are described in terms of their frequency, location, morphology, when they typically occur, and other characteristics. For example, wicket waves occur in the alpha frequency range and are seen unilaterally in the temporal region.
3) Many of the variants are considered normal variants seen in relaxed wakefulness, drowsiness, or different stages of sleep. They are commonly seen in different age groups but are not clinically significant or associated with epilepsy.
This document provides an overview of normal EEG patterns in adults. It begins with a brief history of EEG and then describes the basic electrical activity generated by the brain and how EEG recordings work. It outlines the normal frequency bands seen in EEG - delta, theta, alpha, beta and gamma. Specific normal EEG patterns like the alpha rhythm, vertex waves, sleep spindles and K-complexes are described. It also discusses benign variants and activation procedures. In summary, the document serves as a reference for the typical EEG patterns seen in healthy, awake and sleeping adults.
ECOG involves directly recording cortical electrical activity from the surface of the brain. It is used to localize epileptogenic regions and predict surgical outcomes. There are two main types - intraoperative ECOG during surgery and extraoperative ECOG for longer monitoring. Subdural grids and strips can be placed on the brain surface or depth electrodes can access deeper structures. ECOG is performed by placing electrode arrays on the exposed brain during a craniotomy procedure. It provides valuable data to identify seizure foci but also carries risks like infection if implanted for longer periods.
EEG is used to record the electrical activity of the brain. It uses electrodes placed on the scalp that are smaller than those used in ECGs. EEG can be used to diagnose neurological disorders like epilepsy. There are different types of brain waves like delta, theta, alpha, beta, and gamma waves that are defined by their frequency ranges and locations in the brain. Evoked potentials involve stimulating specific sensory pathways and measuring the electrical response in certain brain areas to help diagnose conditions.
This document discusses artifacts and normal variants that may appear on EEG recordings. It describes various types of artifacts that can originate from patient physiology like eye movements, muscle activity, and heartbeats. It also discusses artifacts from external interference and equipment issues. Normal variants are described like alpha rhythm, sleep transients, and frontal rhythms seen in drowsiness that should not be mistaken for epileptiform activity. The document provides details on identifying features of each artifact and variant to differentiate them from cerebral abnormalities.
EEG variants, are always to be recognized while interpreting the EEG one must be aware of these. Major and most common EEG is variants are discussed in the stated presentation.
Syed Irshad Murtaza.
Este documento describe la electroencefalografía (EEG), un examen que registra la actividad eléctrica del cerebro. Explica cómo se colocan los electrodos en la cabeza siguiendo el sistema 10-20 internacional y cómo se amplifican, filtran y registran las señales cerebrales. Además, describe las diferentes ondas cerebrales como delta, theta, alfa y beta según su frecuencia e implicaciones funcionales y clínicas.
The document discusses the function and history of EEG and describes different brain wave patterns. It summarizes:
1) EEG measures brain waves through electrodes placed on the scalp, detecting voltage fluctuations from neuron action potentials. It uses silver electrodes to obtain accurate readings through the skull and other tissues.
2) There are different brain wave patterns associated with different brain states and sleep stages, including alpha waves during relaxation, beta waves during activity, theta waves during drowsiness, and delta waves during deep sleep.
3) The history of EEG began in 1875 with experiments localizing brain functions, and the first human EEG was recorded in 1924, leading to discoveries of additional wave types and correlations with brain states.
EEG is a technique that measures electrical activity in the brain using electrodes placed on the scalp. It records brain wave patterns which are categorized by frequency into different types like beta, alpha, theta, and delta waves. EEG is used to diagnose brain conditions, locate seizures or lesions, and study cognitive processes. It involves placing electrodes on the scalp, amplifying the tiny electrical signals, filtering out noise, and analyzing the brain wave patterns.
This document discusses EEG signal background and real-time processing. It begins by describing different methods of measuring brain activity, including EEG. It then discusses the source of EEG signals and how they are generated by synaptic activity and summed across electrodes. The document outlines controlling alpha oscillations and using them in brain-computer interfaces. Finally, it discusses real-time processing and closed-loop systems, including buffering data, connecting different recording devices, and creating online analysis pipelines to generate control signals.
EEG measures the electrical activity of the brain through electrodes placed on the scalp. It can detect different wave patterns associated with different brain states. Evoked potentials involve stimulating a sensory pathway and measuring the electrical response along the pathway. This allows localization of lesions. Somatosensory evoked potentials involve stimulating a peripheral nerve like the median nerve and measuring the response along the pathway to detect spinal cord or brain injuries. Auditory evoked potentials involve measuring the brainstem response to a click stimulus to detect acoustic neuromas or other posterior fossa lesions. Both evoked potentials and EMG monitoring are used during surgery to detect injuries.
This document summarizes principles and techniques of intracranial pressure (ICP) measurement and waveform interpretation. It discusses the history of ICP monitoring, indications for monitoring, invasive and non-invasive monitoring techniques, optimal sensor locations, ICP waveform analysis in both time and frequency domains, and guidelines for ICP monitoring in traumatic brain injury. The key points covered include different invasive sensor types, complications of external ventricular drainage, interpreting mean ICP and waveform trends, and using indices like pressure reactivity and variability for management.
This document discusses EEG analysis and machine learning techniques. It describes how EEG data is acquired, preprocessed by removing artifacts, and then features are extracted. Various machine learning algorithms like Bayesian random forests, neural networks, and SVMs are used for prediction and automatic labeling of EEG patterns related to seizures, brain waves during meditation, cognition, and other mental states. It also includes an illustration of electrode positions on the brain and the frequency bands of brain waves.
Periodic Lateralized Epileptiform Discharges (PLEDs) are a pattern seen on EEG consisting of unilateral focal spikes that occur periodically every 1-2 seconds. PLEDs indicate acute or subacute focal pathology in the brain and are associated with an 80% risk of seizures. Common causes include strokes, tumors, infections like herpes simplex encephalitis. PLEDs usually last from days to weeks and resolve once the underlying condition is treated.
The document discusses the historical understanding and physiological mechanisms of intracranial pressure (ICP). It notes that George Kellie in 1823 helped define the closed box concept of the skull. The key points are:
1) ICP is maintained by a balance between brain tissue, blood, and cerebrospinal fluid volumes within the fixed skull space.
2) Common causes of increased ICP include brain tumors, hemorrhages, edema from injuries or infections.
3) Monitoring devices include external ventricular drains and fiberoptic monitors, though all have advantages and disadvantages.
4) Increased ICP can cause herniation and shift brain tissues, reducing blood flow and oxygen, potentially leading to
This document discusses EEG (electroencephalography) and provides an overview of several key topics:
- It outlines the agenda/topics to be covered including the history of EEG, neural activities, action potentials, EEG generation, brain rhythms, recording and measurement techniques, abnormal EEG patterns, aging effects, and mental disorders.
- It describes how EEG signals are generated by the electrical activity of neurons in the brain and measured via electrodes on the scalp. Different brain wave frequencies (rhythms) can be identified in the EEG based on amplitude and frequency.
- Recording, measuring, and processing EEG signals requires electrodes, amplifiers, filters, and techniques like sampling to convert the analog signals to digital
Electroencephalography is the technique used to acquire electrical signals of brain through electrodes which are placed by certain montage. Different wave patterns can be observed which is useful in detecting any abnormal conditions or neurological brain disorders in human beings. There is broad future scope for medical research and creating EEG based equipments for real time applications.
SSPE, dr. amit vatkar, pediatric neurologistDr Amit Vatkar
Subacute sclerosing pan encephalitis (SSPE) also known as Dawson Disease, Dawson encephalitis, and measles encephalitis is a rare and chronic form of progressive brain inflammation caused by a persistent infection with measles virus.
In this presentaion i will a case a sspe and give u some information regarding daignosis and treatment
This document provides an overview of inflammation and its mediators. It begins with introductions to the history and definitions of inflammation. The causes and cardinal signs of inflammation are then discussed. The document outlines the types of inflammatory reactions including acute and chronic inflammation. It then provides details on the vascular and cellular events in acute inflammation. The remainder of the document focuses on the various chemical mediators involved in inflammation, including vasoactive amines, arachidonic acid metabolites, cytokines, chemokines, lysosomal constituents, and other mediators. It also discusses inflammatory cells and the outcomes and resolution of inflammation.
Intracranial pressure - waveforms and monitoringjoemdas
The document discusses intracranial pressure (ICP) waveforms and monitoring. It defines the components of the intracranial vault and describes the normal ICP waveform consisting of P1, P2, and P3 waves representing arterial pulsation, intracranial compliance, and venous pulsation, respectively. It also discusses Lundberg waves including A waves resulting from increased cerebrovascular volume due to vasodilation, B waves related to respiratory fluctuations in PaCO2, and C waves corresponding to Traube-Hering-Meyer fluctuations. The gold standard for ICP monitoring is external ventricular drainage connected to an external strain gauge, which allows CSF drainage but carries risks of infection and hemorrhage. Int
This document discusses different types of artifacts that can appear on an EEG, including physiological and extraphysiological artifacts. It focuses on cardiac artifacts, which can be electrical or mechanical in nature. Electrical cardiac artifact appears as a QRS complex on EEG electrodes due to the electrical activity of the heart. Mechanical cardiac artifacts include pulse artifact seen over vessels and ballistocardiographic artifact from head/body movement with heartbeats. The document provides details on distinguishing cardiac artifacts from epileptiform activity and other EEG patterns. It also discusses electrode artifacts and artifacts from external devices.
The document provides an overview of ECG fundamentals, including the normal conduction system of the heart, principles of ECG recording and interpretation, and criteria for diagnosing common electrocardiographic conditions. It describes how transmembrane ionic currents generate the electrical signal detected as an ECG and outlines the process of depolarization and repolarization. The document also reviews the placement of ECG leads and introduces a 14-point method for clinical interpretation of ECG tracings to analyze rhythm, intervals, axes, waves and voltages. Key arrhythmias, conduction abnormalities, and conditions like myocardial infarction are exemplified.
Clinical teaching on electroencephelographyAquiflal KM
The document discusses a clinical teaching session on electroencephalography (EEG) for 4th year nursing students. The session objectives were to define EEG, describe its indications, mechanism, procedure, and waveforms. EEG measures electrical activity in the brain using electrodes attached to the scalp. It is used to detect problems associated with brain disorders like seizures, tumors, or injuries. During an EEG, technicians attach electrodes to the scalp to record brain wave patterns over 30-60 minutes.
An electrocardiogram (ECG) records the electrical activity of the heart. Small metal electrodes are attached to the skin on the arms, legs, and chest to detect electrical impulses from the heart. The ECG machine amplifies and records these impulses, showing normal and abnormal heart rhythms and any signs of heart damage or disease. A normal ECG tracing shows the P wave, QRS complex, and T wave representing atrial and ventricular contractions and repolarizations. The ECG test takes about five minutes and is painless.
This document discusses ECG artifacts and pitfalls in interpretation. It outlines 10 commandments for proper ECG acquisition to avoid artifacts. Artifacts are classified as internal (physiological) or external (non-physiological). Common artifacts include limb and precordial lead reversals, tremor artifact, computer averaging errors, and electromagnetic interference. Differentiating artifacts from true arrhythmias like ventricular tachycardia is important. Characteristics that can help differentiate include absence of hemodynamic effects, normal complexes within the artifact, and association with movement. Proper electrode placement and equipment grounding can help reduce artifact occurrence.
Salient features of the book are -
- The book provides a shortcut to understand and remember certain specific formulae and points you require to interpret the 12-lead ECG.
- Treatment protocols (in green boxes) for most of the important conditions are also included.
- View sample ECGs as you read along the topics.
- The content is explained in a very simple language to provide good conceptions, written from a student’s point of view.
- People can gain their belief in the book after going through sample ECGs which would be available at www.themedicalpost.net/ecg
- The book competes with the other books available in the market in simplicity, summaries, treatment protocols, live diagrams and regularly updated sample ECGs on the website.
The document provides information on electroencephalography (EEG) and magnetoencephalography (MEG). It discusses the history of EEG, how the signals are recorded, various montages used, neural basis of the signals, analysis methods for EEG including evoked potentials and artifacts. MEG is described as detecting the magnetic fields generated by electrical activity in the brain using SQUIDs, and its increased sensitivity to activity in sulcal walls compared to EEG. Key differences between the two methods are the orientation of measured fields relative to current flow in neurons.
Electrocardiography (ECG or EKG) is a process that records and analyzes the electrical activity of the heart over time using electrodes placed on the skin. It was invented in 1903 by Dutch physician Willem Einthoven, who received the Nobel Prize for his creation. A standard ECG uses 10 electrodes placed in specific locations on the limbs and chest to detect electrical signals produced during each heartbeat. The signals are interpreted by an ECG machine to analyze heart rate, rhythms, and for signs of conditions like heart attacks, damage, or defects. An ECG can provide important information about the structure and function of the heart.
This document provides an overview of EKG waveforms and arrhythmias. It discusses the electrical activity and associated muscle movements in the atria and ventricles that produce the different waves of the EKG. Common arrhythmias like AV block, atrial flutter, and atrial fibrillation are described. The characteristics of normal sinus rhythm as well as abnormal rhythms including premature ventricular contractions, ventricular tachycardia, and ventricular fibrillation are summarized. The document provides a guide for interpreting EKG readings to identify arrhythmias and dysrhythmias.
This document summarizes the design of an EEG circuit and data acquisition system. It includes block diagrams of the EEG amplifier board and analog-to-digital converter board. The EEG amplifier uses a two-stage design with gains of 50 and 390. The proposed analog-to-digital converter is a Keithley KPCI-1307 card capable of 100k samples/second. Software options for the card include VHDL implementation on an Altera board or using DriverLINX APIs. Testing showed the system could successfully record eyebrow raises and eye blinks.
This document summarizes key concepts about EEG circuit design and analysis. It discusses electrode circuits, instrumentation amplifiers, chopper-stabilized low-noise amplifiers, two-stage op-amps, equivalent circuit models, EEG recordings from different conditions, hardware block diagrams, the Nyquist theorem, bipolar vs monopolar recordings, artifacts from EMG, eye blinks, EKG, line noise, reviewing EEG based on voltage, frequency, location, and transient events, normal and abnormal distributions of EEG data, constructing life span normative databases, and related BCI research goals and challenges.
An electrocardiogram (ECG or EKG) is a test that records the electrical activity of the heart. It does this by detecting tiny voltage changes on the skin caused by the heart muscle during each heartbeat. A standard 12-lead ECG involves placing 10 electrodes on the patient's limbs and chest to record 12 different electrical signals that provide different views of the heart. The ECG can help diagnose abnormal heart rhythms and detect signs of damage to heart muscle.
This document provides information on EEG (electroencephalogram) and ECG (electrocardiography). It describes that EEG uses electrodes placed on the scalp to record brain's electrical signals and identify issues like seizures, while ECG uses electrodes to record and graph the heart's electrical activity over time to diagnose cardiac conditions. It discusses the different types of EEGs and ECGs, what the brain and heart wave patterns indicate, and their uses, workings, advantages and disadvantages.
An electrocardiogram (ECG or EKG) records the electrical activity of the heart over time through electrodes placed on the skin. It shows five main components - P wave, QRS complex, and T wave - that represent the spread of electrical impulses through the heart during each heartbeat. Doctors can analyze features of the EKG like interval durations and waveform shapes to detect abnormalities and disorders of the heart's rhythm or muscle tissue. In this experiment, students will record their own EKG, identify the components, calculate heart rate, and observe how the tracing changes when the electrode leads are switched to simulate a myocardial infarction.
Electrocardiography is the process of producing an electrocardiogram, a recording – a graph of voltage versus time – of the electrical activity of the heart using electrodes placed on the skin
5-hydroxytryptamine or 5-HT or Serotonin is a neurotransmitter that serves a range of roles in the human body. It is sometimes referred to as the happy chemical since it promotes overall well-being and happiness.
It is mostly found in the brain, intestines, and blood platelets.
5-HT is utilised to transport messages between nerve cells, is known to be involved in smooth muscle contraction, and adds to overall well-being and pleasure, among other benefits. 5-HT regulates the body's sleep-wake cycles and internal clock by acting as a precursor to melatonin.
It is hypothesised to regulate hunger, emotions, motor, cognitive, and autonomic processes.
The skin is the largest organ and its health plays a vital role among the other sense organs. The skin concerns like acne breakout, psoriasis, or anything similar along the lines, finding a qualified and experienced dermatologist becomes paramount.
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Mercurius is named after the roman god mercurius, the god of trade and science. The planet mercurius is named after the same god. Mercurius is sometimes called hydrargyrum, means ‘watery silver’. Its shine and colour are very similar to silver, but mercury is a fluid at room temperatures. The name quick silver is a translation of hydrargyrum, where the word quick describes its tendency to scatter away in all directions.
The droplets have a tendency to conglomerate to one big mass, but on being shaken they fall apart into countless little droplets again. It is used to ignite explosives, like mercury fulminate, the explosive character is one of its general themes.
Kosmoderma Academy, a leading institution in the field of dermatology and aesthetics, offers comprehensive courses in cosmetology and trichology. Our specialized courses on PRP (Hair), DR+Growth Factor, GFC, and Qr678 are designed to equip practitioners with advanced skills and knowledge to excel in hair restoration and growth treatments.
These lecture slides, by Dr Sidra Arshad, offer a simplified look into the mechanisms involved in the regulation of respiration:
Learning objectives:
1. Describe the organisation of respiratory center
2. Describe the nervous control of inspiration and respiratory rhythm
3. Describe the functions of the dorsal and respiratory groups of neurons
4. Describe the influences of the Pneumotaxic and Apneustic centers
5. Explain the role of Hering-Breur inflation reflex in regulation of inspiration
6. Explain the role of central chemoreceptors in regulation of respiration
7. Explain the role of peripheral chemoreceptors in regulation of respiration
8. Explain the regulation of respiration during exercise
9. Integrate the respiratory regulatory mechanisms
10. Describe the Cheyne-Stokes breathing
Study Resources:
1. Chapter 42, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 36, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 13, Human Physiology by Lauralee Sherwood, 9th edition
- Video recording of this lecture in English language: https://youtu.be/Pt1nA32sdHQ
- Video recording of this lecture in Arabic language: https://youtu.be/uFdc9F0rlP0
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
10 Benefits an EPCR Software should Bring to EMS Organizations Traumasoft LLC
The benefits of an ePCR solution should extend to the whole EMS organization, not just certain groups of people or certain departments. It should provide more than just a form for entering and a database for storing information. It should also include a workflow of how information is communicated, used and stored across the entire organization.
Histololgy of Female Reproductive System.pptxAyeshaZaid1
Dive into an in-depth exploration of the histological structure of female reproductive system with this comprehensive lecture. Presented by Dr. Ayesha Irfan, Assistant Professor of Anatomy, this presentation covers the Gross anatomy and functional histology of the female reproductive organs. Ideal for students, educators, and anyone interested in medical science, this lecture provides clear explanations, detailed diagrams, and valuable insights into female reproductive system. Enhance your knowledge and understanding of this essential aspect of human biology.
2. Introduction:
Although EEG is designed to record cerebral activity,
it also records electrical activities arising from sites
other than the brain.
The recorded activity that is not of cerebral origin is
termed artifact and can be divided into physiologic
and extraphysiologic artifacts.
While physiologic artifacts are generated from the
patient, they arise from sources other than the brain
(ie, body).
Extraphysiologic artifacts arise from outside the
body (ie, equipment, environment).
3.
The systematic approach of recognition, source
identification, and elimination of artifact is an
important process to reduce the chance of
misinterpretation of the EEG and limit the potential
for adverse clinical consequences.
4. Principles used to discriminate artifacts
from EEG signals:
Physiological activity has a logical topographic field
of distribution with an expected fall off of voltage
potentials.
Artifacts have an illogical distribution that defies the
principles of localization
7.
The heart produces 2 types of artifacts
Electrical
Mechanical
Both types are time locked to cardiac contractions and are most
easily identified by their synchronization with complexes in the
ECG channel
The electrical artifact actually is the ECG, as recorded from head
electrodes.
The P wave and T wave are usually not visible, because of the
distance from the heart and the suboptimal axis.
Essentially, the artifact is a poorly formed QRS complex.
Most prominent when the neck is short.
8.
The complex usually is diphasic, but some EEGs may depict it as
either monophasic or triphasic.
Overall, the artifact is best formed with referential montages
because of their greater interelectrode distances and ECG field’s
approx. equal potential across the head.
Because of the equipotential field, montages with an average
reference have minimal ECG artifact.
With bipolar montages, the artifact occurs with maximum
amplitude and clearest QRS morphology over the temporal
regions and often is better formed and larger on the left side.
The R wave is most prominent in channels that include the ear
electrodes and may demonstrate a dipole with A1 positive and
A2 negative.
9. Cardiac artifact
ECG artifact is identified by its fixed period and morphology and is limited to T3-A1
channel in this bipolar montage
11.
ECG artifact may occur inconsistently by not being
present with every contraction of the heart and may have
an irregular interval when a cardiac arrhythmia is present.
In either situation, it may be identified by its temporal
association with the QRS complexes in an ECG channel.
Cardiac pacemakers produce a different electrical artifact.
it is distinct from ECG artifact in both distribution and
morphology.
Pacemaker artifact is generalized across the scalp and
comprises high frequency, polyphasic potentials with a
duration that is shorter than ECG artifact.
12. Pacemaker artifact
Transients comprising very fast activity recur in channels with the A1 and A2
electrodes. The transients are simultaneous to similar discharges in the ECG channel
and correspond to a permanent pacemaker’s output
13.
Mechanical artifact from the heart arises through the circulatory
pulse and may be considered as a type of electrode artifact.
It occurs when an electrode rests over a vessel manifesting the
pulse and appears as a periodic slow wave with a regular
interval that follows the ECG artifact’s peak by about 200 msec.
Sometimes it has a saw-tooth or sharply contoured
morphology.
It occurs most commonly over the frontal and temporal regions
and less commonly over the occiput; however it may be present
anywhere.
Pulse artifact is easily identified by touching the electrode
producing it.
This both confirms the movement of the electrode with the
pulse and alters its appearance on the EEG as pressure is
applied
14. Pulse artifact
Focal slow waves at the left occiput follow each heart beat, as indicated in the ECG
channel. The slow waves are artifact due to electrode movement and were eliminated by
repositioning the O1 electrode
16. another form of mechanical
Ballistocardiographic artifact is
cardiac artifact.
It results from the slight movements of the head or body that
occur with cardiac contractions.
This partly may be due to the pulsatile force on the aortic arch
from the abrupt redirection of blood flow.
Ballistocardiographic artifact is similar in morphology to pulse
artifact but is more widespread.
If it is due to electrode lead movement, it may involve one or a
few electrodes.
If it is due to movement of the head on a pillow, it involves a
collection of posterior electrodes and is altered by repositioning
the head or neck on a pillow.
Occasionally, ballistocardiographic artifact is generalized.
17.
Distinguishing features versus Benign Epileptiform Transients of
Sleep :
Like BETS, ECG artifact typically comprises individual
transients that are low amplitude, are morphologically
conserved, and occur in the midtemporal regions.
The temporal correspondence to simultaneously recorded
ECG is the best means to differentiate these two waves.
If an ECG channel is not present, identifying the wave in
full wakefulness excludes BETS and identifying a regular
interval between the waves supports ECG artifact.
18.
Distinguishing features versus focal ictal and interictal Epileptiform
discharges:
ECG artifact may disrupt the EEG’s background activity
similarly to epileptiform discharges.
Moreover, it usually is diphasic or triphasic with a fast
component that has a duration within the spike range.
When the artifact occurs either with a highly regular interval or
can be compared to an ECG channel, differentiating it from
interictal epileptiform discharges is straightforward.
An episodic occurrence pattern requires careful scrutiny of the
morphology and location.
ECG artifact almost always occurs in channels that include
electrodes that are low on the head, especially ear electrodes.
19.
When a wave only occurs in such channels and has a perfectly
conserved morphology, it is likely to be ECG artifact.
IEDs show greater variation between occurrences than ECG
artifacts even when they recur as the same wave type, that is,
they vary more in amplitude, duration, contour, and location
than ECG artifact.
Paroxysmal tachycardia may produce ECG artifact that
resembles an ictal pattern.
Identifying it as artifact relies on the features that are used for
distinguishing IEDs, including preservation in morphology and
temporal association with the QRS complex in an ECG channel.
The regular interval feature also is helpful because the artifact
also will be present at times between the episodes of
tachycardia.
20. Lateralized Epileptiform
Distinguishing features versus Periodic
Discharges:
The diphasic and triphasic morphology and periodic
occurrence pattern are features that PLEDs and ECG
artifact share.
Differentiating these waves is straightforward when
comparison to an ECG channel is possible.
When an ECG channel is not present, the regularity of the
intervals between the transients is the key distinguishing
feature.
PLEDs usually are not nearly as regular in their interval as
ECG artifact.
21. conditions for recording an
This is especially true because the
EEG do not produce significant changes in heart rate.
Other distinguishing features are distribution and frequency.
Although ECG artifact may be unilateral, it is often is bilateral,
and PLEDs, by definition are not bilaterally synchronous.
Bilateral periodic epileptiform discharges (BiPEDs) are
bilaterally synchronous, but BiPEDs usually have large,
bifrontal fields. ECG artifact is usually maximal in the two
temporal regions.
The BiPEDs of CJD provide one exception to this distinguishing
feature because they may be b/l without a large field for a time
during the course of the illness.
22.
Frequency is a less reliable means for differentiation.
Most ECG artifact will be at 1Hz or faster because a heart
rate slower than 60 bpm is unusual.
In contrast, PLEDs usually occur with intervals greater
than 1 sec.
However, the interval between PLEDs varies, especially
across different etiologies.
24. Types:
Electrode pop
Electrode contact
Electrode/lead movement
Perspiration
Salt bridge
Movement artifact
25. as one of two disparate
Electrode artifacts usually manifest
waveforms, brief transients that are limited to one electrode and
low frequency rhythms across a scalp region.
The brief transients are due to either spontaneous discharging
of electrical potential that was present between the electrode or
its lead.
The spontaneous discharges are called electrode pops, and they
reflect the ability of the electrode and skin interface to function
as a capacitor and store electrical charge across the electrolyte
paste or gel that holds the electrode in place.
With the release of the charge there is a change in impedance,
and a sudden potential appears in all channels that include the
electrode.
26.
This potential may be superimposed on the background
activity or replace it.
Sometimes more than one pop occurs within a few
seconds.
Electrode pop has a characteristic morphology of a very
steep rise and a more shallow fall.
27. Electrode pop
The nearly vertical rise followed by the slower fall at the F3 electrode is typical of electrode pop
artifact. Also typical is an amplitude that is much greater than the surrounding activity, a field that
is limited to one electrode, and repeated recurrence within a short time
28.
Poor electrode contact or lead movement produces
artifact with a less conserved morphology than electrode
pop.
The poor contact produces instability in the impedance,
which leads to sharp or slow waves of varying
morphology and amplitude.
These waves may be rhythmic if the poor contact occurs
in the context of rhythmic movement, such as from a
tremor.
Lead movement has a more disorganized morphology
that does not resemble true EEG activity in any form and
often includes double phase reversal, that is, phase
reversals without the consistency in polarity that indicates
a cerebrally generated electrical field.
29. Electrode Movement artifact
The focal slowing in the T4-T6 and T6-O2 channels has no field beyond T6 electrode and
has the oscillations typical of rhythmic electrode movement
30. Lead movement
Multiple channels demonstrate the artifact through activity that is both unusually high
amplitude and low frequency and also disorganized without a plausible field
31.
The smearing of the electrode paste between electrodes to form
a salt bridge or the presence of perspiration across the scalp
both produce artifacts due to an unwanted electrical connection
between the electrodes forming a channel.
Perspiration artifact is manifested as low amplitude, undulating
waves that typically have durations greater than 2 sec; thus,
they are beyond the frequency range of cerebrally generated
EEG.
Slat bridge artifact differs from perspiration artifact by being
lower in amplitude, not wavering with low frequency
oscillation, and typically including only one channel
It may appear flat and close to isoelectric.
32. Sweat artifact
The decreased amplitude and very low frequency oscillations are present diffusely,
which is consistent with the whole scalp’s involvement. The recurring sharp waves
across most channels are ECG artifact.
33. Sweat artifact
This is characterized by very low-frequency (here, 0.25- to 0.5-Hz) oscillations. The
distribution here (midtemporal electrode T3 and occipital electrode O1) suggests sweat
on the left side
34. Salt bridge artifact
Activity in channels that include left frontal electrodes is much lower in amplitude and frequency
than the remaining background. The lack of these findings when viewed in a referential montage
confirms that an electrolyte bridge is present among the electrodes involved.
35.
Distinguishing features versus ocular artifact:
Slow roving eye movements produce artifact that has a
frequency and field similar to that perspiration artifact.
The key distinguishing feature is the rhythmicity, phase
reversal, and broad, bifrontal field of the eye movements.
Roving eye movements occur with drowsiness and are an
involuntary and repeated horizontal ocular movement.
The movements have a relatively constant period and
demonstrate a phase reversal because of the eyes’ dipoles.
With right gaze, the field around the rt frontotemporal
electrodes becomes more positive and the fields around the left
frontotemporal electrodes becomes more negative.
This produces a phase reversal not seen with salt bridge
artifact, even when the low amplitude activity happens to be
rhythmic.
36.
Distinguishing features versus IEDs:
Electrode pop resembles IEDs because both occur as
paroxysmal, sharply contoured transients that interrupt
the background activity.
However, electrode pop involves only one electrode.
Therefore, it does not have a field indicating more gradual
decrease in the potential’s amplitude across the scalp
The lack of a field including multiple electrodes is highly
rare for IEDs except in young infants.
The morphology of electrode pop also is different from
spikes by having a much steeper rise and much slower
fall.
39. produce EEG artifact
Numerous types of external devices
and may do so through the electrical fields they generate
or through mechanical effects on the body.
The most common external artifact is due to the
alternating current present in the electrical power supply.
This noise is usually medium to low amplitude and has
the monomorphic frequency of the current, which is 60 Hz
in North America and 50 Hz in much of the rest of the
world.
The artifact may be present in all channels or in isolated
channels that include electrodes that have poorly matched
impedances.
40. 60 Hz artifact
The very high frequency artifact does not vary and is present in the posterior central
region, which does not typically manifest muscle artifact. This example was generated
by eliminating the 60Hz notch filter.
41. from falling
Electrical noise may also result
electrostatically charged droplets in an IV drip.
A spike like EEG potential results, which has the
regularity of the drip.
42. IV drip
Triphasic and polyphasic transients are occurring simultaneous to the falling of drops in
an IV infusion. This EEG corresponds to electrocerebral inactivity.
43.
Electrical devices may produce other forms of noise.
Anything with an electric motor may produce high
amplitude, irregular, polyspike like, or spike like artifact.
This is due to the switching magnetic fields within the
motor.
The artifact occurs with the motor’s activity; thus, it may
be constant or intermittent, as is the case with infusion
pumps.
Mechanical telephone bells are the classic source for a
more sinusoidal form of this artifact but are increasingly a
less common source of the intermittent form of this
artifact.
44. Electrical motor
The very high frequency activity suggests an electrical source, and the fixed
morphology and repetition rate indicate an external device. This was caused by an
electric motor within the pump.
45.
Mechanical devices such as ventilators and circulatory pumps
usually produce artifacts with slower components than other
electrical devices.
Their artifact may resemble ballistocardiographic or other
electrode artifact in that the artifact is generated by movement
of electrodes or least as the body is moved by the device.
The artifact typically repeats with a fixed interval and is a slow
wave or a complex including a mixture of frequencies
superimposed on a slow wave.
Two exceptions to this typical artifact pattern are the artifact
resulting from ventilators that deliver air with an oscillating,
high pressure burst.
46. frequency artifact in
This may produce rhythmic higher
channels that include electrodes either nearer the pharynx
or in contact with a fixed surface, such as a pillow or bed.
Thus, it may appear as intermittent, rhythmic activity and
may be similar to alpha frequency activity when it is
across the posterior head.
Its highly monomorphic frequency and fixed repetition
interval are its characteristic features.
Overall, the number of devices that may produce artifact
and the variety of artifacts that each device may produce
based on its settings greatly complicates the job of
recognizing artifacts based on specific features.
47. Mechanical ventilator
The artifact present across the right occiput has the fixed morphology and repetition rate of
mechanical artifact. Its location relates to the head resting on the electrodes involved and
moving at times of rapid airflow. The Fp2 and F4 electrodes generate artifact due to poor
contact
48. Circulatory pump
Sharply contoured, b/l frontal repetitions occur with a fixed interval and are due to a
pump providing circulatory support and extracorporeal membrane oxygenation. Pulse
artifact is present in multiple channels and most apparent in the A2-T4 channel
50.
However, the challenge may be met by realizing that artifacts
from external devices usually produce waveforms, that are
highly dissimilar to cerebrally generated wave forms.
Because of this, highly unusual waveforms should always be
suspected as artifact.
Proving that the wave is artifact usually rests on the
technologist recording the EEG.
On seeing the unusual wave, the technologist should search the
environment for possible causes and test the possibilities
whenever possible by observing for a temporal association
between the device’s action and the artifact.
When such information from the technologist is not present,
the assumption that an unusual wave is artifact is preferred by
convention over an assumption of abnormality.
51.
Distinguishing features versus Ictal patterns:
Because external device artifact may include fast
components and demonstrate evolution within an
occurrence, it may resemble ictal patterns.
This artifact is most easily distinguished from ictal
patterns by its short duration, regular repetition, and
highly preserved morphology.
Almost all sources for artifact produce either continuous
artifact or artifacts that last less than several seconds and
repeat as identical waves at least several times a minute.
Such an occurrence pattern is very unusual for a seizure.
52.
Distinguishing features versus PEDs:
When an external device causes intermittent artifact, it
often has a regular interval and may be similar to PEDs in
its periodicity.
However, this type of artifact rarely has the diphasic or
triphasic morphology of PEDs and usually has a
distribution that is highly unusual for PEDs, such as the
inclusion of electrodes that are not adjacent to one
another.
Also unusual for PEDs is a generalized occurrence, which
is common for device artifact.
55.
Movement during the recording of an EEG may product
artifact through both the electrical fields generated by
muscle and through a movement effect on the electrode
contacts and their leads.
Although the muscle potential fields are the signals
sought by electormyographers, they are noise to
electroencephaographers.
Indeed, EMG activity is the most common and significant
source of noise in EEG.
EMG activity almost always obscures the concurrent EEG
because of its higher amplitude and frequency.
56. Muscle artifact
The high amplitude, fast activity across the b/l ant. region is due to facial muscle
contraction and has a distribution that reflects the locations of the muscles generating it.
Typical of muscle artifact, it begins and ends abruptly.
57. of clinical EEG and too
Its frequency is higher than that
fast to be visually estimated.
However, it may appear regular and in the beta frequency
band or as repetitive spikes if the high frequency filter
(low pass filter) is set at 35 Hz or less.
Without this filtering, EMG artifact usually has a more
disorganized appearance because the individual myogenic
potentials overlap with each other.
Occasionally, individual potentials are discernible.
This occurs with involuntary motor unit activity such as
from fibrillations and has a classic EMG wave appearance.
58.
The duration of EMG artifact varies according to the
duration of the muscle activity; thus, it ranges from
less than a second to an entire EEG record.
Similarly, the distribution varies; however, the
artifact occurs most commonly in regions with
underlying muscle, specifically the frontalis and
masseters.
Thus, EMG artifact most commonly occurs in
channels including the frontal and temporal
electrodes.
59. EMG artifact
The stereotyped potentials at the T3 electrode are EMG artifact. The potentials’ duration
are briefer than cerebrally generated spikes, and unlike cerebrally generated activity,
they have a field limited to one electrode.
60.
Repetitive EMG artifact may occur with photic
stimulation as a time locked facial muscle response
to the flash of light.
This is termed a photomyogenci or photomyoclonic
response and occurs over the frontal and periorbital
regions bilaterally.
It may extend to include a larger region when the
myoclonus involves the neck or body.
Larger regions of myoclonus commonly produce
simultaneous electrode and movement artifact.
61.
The photomyogenic response has a 50 msec latency
from the stobe’s flash and, therefore, may occur
synchronously with the occipital photic stimulation
driving response.
It may be present with eyes opened or closed but
tends to occur more often with eyes closed.
Its occurrence with eyes opened may be
accompanied by ocular artifact.
Obviously, it disappears immediately when photic
stimulation is stopped.
62. Photomyogenic artifact
Simultaneous to the 6Hz strobe stimulations are transients across the frontal region that
reflect an involuntary muscle contraction.
63.
Although the oropharyngeal muscles are not near
EEG electrodes, swallowing and talking also produce
artifact.
This is partly EMG artifact from the pharyngeal
muscles and partly due to the tongue’s inherent
dipole.
The tongue’s tip is electronegative compared to its
base; thus movement of the tongue toward or away
from EEG electrodes alters the overall electrical field
around them.
This is termed as glossokinetic artifact.
64.
The resulting artifact has a wide field with maximal
amplitude frontally and comprises isolated slow
waves, delta frequency range activity, or, more
typically, slowing with superimposed faster
frequencies.
It often also includes simultaneous EMG artifact.
Glossokinetic artifact is highly rhythmic when the
tongue has a tremor or the patient is a nursing infant.
66.
Distinguishing features versus beta activity:
Because the frontalis muscle runs over the frontal
central region, EMG artifact often co-localizes with
the region of maximum beta activity and resembles it
with its characteristic frequency greater than 25 Hz.
Morphological difference is the principal
distinguishing feature.
EMG artifact has a sharper contour and less
rhythmicity when the high frequency filter is set at
more than 60Hz.
67.
When it occurs as a rhythm within the beta
frequency range, it does so as individual EMG
potentials that have durations of less than 20 msec
but are separated by an interval that gives it a beta
frequency range appearance.
The significant variation in this interval provides
another distinguishing feature, especially when the
interval becomes so brief that the potentials appear
continuous.
Such very fast activity is beyond the beta frequency
range and almost always indicates muscle artifact.
68.
Distinguishing features versus Paroxysmal fast activity:
EMG artifact and PFA both develop abruptly and include
high-amplitude, very fast activity.
However, they differ in their frequency components.
Muscle artifact contains a greater number of frequencies
and, therefore, appears more disorganized.
This basis in a superimposition of fast frequencies also
makes muscle artifact appear slightly different with each
occurrence.
PFA has a more organized morphology that is
stereotyped among occurrences.
69.
Versus photoparoxysmal response:
Because photoparoxysmal responses may have a maximal
field frontally, their field may overlap with that of
photomyogenic artifact.
Furthermore, photomyogenic artifact has a spike-like
morphology due to its basis as individual motor unit
potentials.
Differentiating the two patterns depends on morphologic
differences and the degree of association between the
transients and the flashing stimulation.
Photomyogenic artifact is very sharply contoured and
lacks after-going slow waves.
70.
Furthermore, it almost always occurs across a broad
range of stimulation frequencies, occurs commonly
at almost every stimulation frequency used, and
does not persist beyond the period of stimulation.
This contrasts with photoparoxysmal responses that
typically occur at one or two stimulation frequencies,
may not be time-locked with the stimulations, and
may continue beyond the stimulation interval.
73.
Most eye artifacts are due to each eye’s inherent 100mV
electrical dipole.
The dipole is oriented along the corneal-retinal axis and
is positive in the direction of the cornea and negative in
the direction of the retina.
The dipole becomes relevant to the EEG recording when
it becomes a moving electrical field, as occurs with
changes in gaze and eye opening and closure.
Vertical eye movements accompany eye opening and
closure with deviation upward which is called Bell’s
phenomenon.
74.
Eyelid movement with its myogenic potentials also may
contribute to ocular artifact with eye opening and closure.
Blinking produces an ocular artifact because of the rapid
movement of the eyes both up and down and appears on
the EEG as a bifrontal, diphasic, synchronous slow wave
with a filed that does not extend beyond the frontal
region.
The amplitude of the artifact decreases quickly with
greater distance from the orbits.
The wave is maximum amplitude and surface positive at
the frontal poles.
Because the artifact is produced by deviation of the eyes
upward, the negative end of the dipoles is not detectable
with conventional montages.
75. Blink artifact
Bifrontal, diphasic potentials with this morphology and field are reliably eye blink
artifact.
76.
Repetitive blinks usually appear as a sequence of the slow wave
ocular artifacts and thus resemble rhythmic delta activity.
However, blepharospasm may produce an artifact with a faster
frequency.
Although ocular flutter involves vertical eye movements, it
differs from repetitive blinks by being more rapid and having
lower amplitude.
Because of this, its EEG artifact is more rhythmic and lower
amplitude, which gives it a greater resemblance to rhythmic
delta activity.
When periocular muscle contractions accompany the eye
movements of ocular flutter, the resulting artifact may appear
as a run of bifrontal spike and slow wave complexes.
The spike arises from the brief EMG artifact related to the
periocular contraction.
77. Eye flutter artifact
Medium amplitude, low frequency activity that is confined to the frontal poles is
identified as ocular artifact through its morphology. Compared to blink artifact, flutter
artifact typically has a lower amplitude and a more rhythmic appearance
78. are detectable with
Both ends of the eyes’ dipoles
lateral eye movements.
This is observed with greater positivity on the side to
which gaze is directed and greater negativity on the
opposite side.
With bipolar montages, positive and negative phase
reversals are seen at the F7 and F8 electrodes.
79. Lateral eye movement
Although a horizontal, frontal dipole is the key finding with lateral eye movements, the
artifact is also distinguished by its morphology, which has a more abrupt transition
between the positive and negative slopes that blinks and most flutter. The initial gaze in
this segment is to the right.
80.
Ocular artifact from lateral gaze is most apparent during
drowsiness, when the eyes demonstrate repeated, slow lateral
movements.
This produces rhythmic, slow artifact anteriorly with a field
that is maximum at the frontal poles and temples and a
frequency that is less than 1Hz.
Because the amplitude is also low, the wave also resembles an
unstable baseline for the superimposed EEG activity.
The most characteristic feature of the low amplitude slowing
due to roving eye movements is the opposite polarity of the
slowing in the left and right frontotemporal regions.
This artifact typically occurs intermittently and is accompanied
by slowing of the alpha rhythm.
81. Slow roving eye movement
Unlike the saccades of the lateral gaze, slow roving movement artifact does not have
abrupt changes. Instead, it reflects the smooth lateral movements with phase reversing
slow activity.
83. lateral eye movements
The EEG during more rapid
sometimes includes a single MUP from contraction of
the lateral rectus muscle.
This low amplitude transient is termed a lateral rectus
spike and usually is present at the F7 (left gaze) or F8
electrode (right gaze)
The lateral rectus spike may be followed immediately
by slower eye movement artifact in the same location
and this may result in what appears as one wave with
a morphology that resembles a focal IED.
85.
Although they are lateral gaze movements, the rapid
eye movements of REM stage sleep have a
morphology that differs from lateral gaze during
wakefulness
REM artifact appears as asymmetric waves with a
quicker rise that fall.
Of course, their location is the same as the other
artifacts produced by lateral gaze.
86.
Distinguishing features versus Delta activity:
Isolated monomorphic frontal slow waves and frontal
intermittent rhythmic delta activity (FIRDA) have the
same wave duration and similar field to ocular artifact
from eye opening and closure.
Blinks are more similar to isolated slow waves, and eye
flutter is more similar to FIRDA.
The field is the key distinguishing feature between ocular
artifact and delta activity.
Unlike delta activity, ocular artifact does not extend into
the central region.
However, a morphologic difference also exists due to
ocular artifact’s sharper contour.
87.
The two also may be distinguished based on recognized
eye movements, as described in the technologist’s notation.
If notation is not present, then identification may be based
on whether the wave is absent in drowsiness and sleep,
states in which the eyes are closed.
Using both supraorbital and infraorbital electrodes is the
most definitive means for differentiation.
Ocular artifact produces a phase reversal between
infraorbital electrode and supraorbital electrode channels
because the area of maximum potential exists between the
electrodes.
In contrast, the area of maximum potential for cerebrally
generated slowing is above the orbits; thus, it does not
produce a phase reversal between these channels.
88.
Distinguishing features versus IEDs:
When the slow wave artifact of ocular flutter occurs in
combination with the faster frequency artifact from eyelid
movement, a compound wave results that appears to be a
bifrontal spike and slow wave complex.
Although the frontal poles may be the center of a spike and
slow wave complex's field, this is an unusual location.
When the bilateral spike and slow wave of a generalized IED
has a phase reversal, it usually is at F3 or F4.
A focal spike and wave may occur at one frontal pole but it
would not have bilateral symmetry.
Spike morphology also may distinguish these waveforms.
89.
Because it is generated from muscle artifact, the
spike of the stimulated spike and wave complex is
less stereotyped that the IED.
Lastly, true IEDs usually occur in states beyond light
drowsiness, which is the state for ocular flutter.
Even when the IEDs occur only with drowsiness,
they continue to occur into stage II non-REM sleep.
Another compound wave results from the
combination of the brief myogenic potential from the
lateral rectus and the slow wave artifact from lateral
gaze.
90.
This appears especially similar to an IED because the
lateral rectus spike results form a single motor unit
potential and is, therefore, relatively stereotyped
across occurrences like the spike of an IED.
It also occurs in the anterior temporal region, which
is a region that often produces focal IEDs.
Distinguishing lateral rectus spikes form IEDs
depends on the lateral rectus spike’s consistent low
amplitude, presence only at F7 and F8, and absence
on some lateral eye movements that still
demonstrate the slow wave artifact.
91. in their amplitude
IED spikes typically vary more
and location, even if the variations only minor going
slow wave, which is the opposite of the lateral gaze
artifact in which the slow wave may occur without
the spike.
A shifting asymmetry between F7 and F8 is not
helpful because some individuals with temporal lobe
epilepsy have bilateral independent temporal IEDs.
93.
Artifacts are usually easily recognized by experienced
EEGer.
The process of visual analysis, remontaging, and digital
filtering allow identification of most physiologic and
nonphysiologic artifacts.
Reviewing an epoch of EEG in a different montage may
allow the EEGer to determine that a particular waveform
does not have a physiologic field, and thus be more
certain of its artifactual nature.
Digital filters can be applied and removed multiple times,
and can significantly improve interpretation of EEG
contaminated by artifacts by allowing specific frequencies
to be removed from the digital display.
95. Use of Band Pass Filters:
If the analysis is restricted to certain frequency bands, an
automated algorithm can be designed to only analyze
activity in this frequency band.
For ex., a 1 to 20Hz band pass may be used to remove
muscle artifact.
This method is not very useful for analysis of the entire
bandwidth of EEG, as artifacts can occur at any
frequency.
Even for very narrow frequency bands, there may be
significant artifact remaining after band pass filtering.
The process of filtering may significantly alter the
appearance of EEG and make subsequent identification of
artifacts more difficult.
96. Manual rejection of artifact
segments:
visually reviews the
In this case, a technologist or EEGer
entire EEG recording and marks segments with artifacts.
This is a reliable method, and may detect some artifact
that would be missed by automated techniques.
It is time consuming, however, and reader fatigue may
become problematic for long or multichannel recordings.
Subtle or brief artifacts may not be identified, and
different readers may have different thresholds for
rejection.
This method is only possible for offline(not real time)
digital analysis.
97. Automatic rejection of artifact
segments:
This technique rejects short segments of EEG if the
segment exceeds predefined thresholds.
These thresholds can be simple analysis of the EEG
channels themselves such as amplitude, numbers of zero
crossings, or 60Hz artifact.
If a segment shows very high amplitude, it is eliminated.
Some techniques use other special electrodes to identify
artifact signals, such as EOG,EMG, EKG or
accelerometers.
If the signal in these channels exceeds a threshold, the
segment of EEG will be rejected.
98. online or offline.
This technique can be used
This automatic rejection techniques will not identify
all possible artifacts, especially for ambulatory
patients or in electrically hostile environments.
Again, the entire EEG segment is rejected if the
threshold is exceeded, so, some useful EEG may be
eliminated.
99.
Source decomposition techniques aim to decompose
EEG signals into individual components that
represent EEG and others that represent artifact.
Once the artifact component is identified, it is
removed, and other remaining signal is recomposed.
Examples of these methods include spatial filtering,
principal component analysis, and independent
component analysis.
Wavelet based and neural network algorithms allow
adaptation of this method to a wider variety or
artifact types.
100. Automated subtraction of artifact:
These methods aim to identify artifact and to remove
only the artifact from the recording, leaving a clean
EEG for digital analysis.
Simultaneously recorded EOG or EKG can be
subtracted from an EEG channel using a computer.
The algorithm must be adapted for each individual
patient.
These techniques may result in distortion of the EEG
signal, as the EOG also contains some normal brain
signals that will be subtracted.