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- 1. Non- Epileptiform AbnormalEEG pattern for adult Presenter : Dr Addis F .(NR3) Moderator : Dr Berhanu S. (Consultant neurologist)
- 2. Outline • Introduction • FocalNonepileptiform Activity • Generalized Nonepileptiform Activity • Reference
- 3. Introduction EEG isconsidered abnormal if it has findings known to be associated with a pathologic or disease state EEG abnormalities can be categorized in a variety of ways Abnormal expressions of normally occurring rhythms Inherently abnormal rhythms Repetitive or periodic patterns Epileptiform abnormalities Epileptiform /Non epileptiform abnormal EEG pattern
- 4. Conti… Non epileptiformabnormal EEG pattern • Abnormal alpha /beta pattern • Slowing • Repetitive patterns • Sleep architecture abnormalities • Non- epileptiform abnormalities are common in hospital and ICU EEGs
- 5. Conti…. Non epileptiform abnormalityprovide valuable information to guide management of patients with altered sensorium ,rapidly progressive dementia ,Toxic /metabolic encephalopathies ,coma & brain death . For ease of discussion, we can classify Non epileptiform abnormal EEG pattern Focal Non epileptiform abnormal EEG pattern Generalized Non epileptiform abnormal EEG pattern
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- 7. Focal Abnormalities • Focalabnormalities on the EEG provide electrographic evidence of a localized abnormal cerebral function. • They are not specific for etiology and may be seen with many different underlying structural lesions that affect the brain. • They may also be encountered as a temporary nonstructural physiological effect
- 8. Focal Non -Epileptic EEG abnormalities • Abnormalities of alpha rhythm • Abnormalities beta activity • Focal slowing activity • Periodic discharges
- 9. Abnormalities of Posteriorrhythm Asymmetry Amplitude( > 50% for Rt) The left hemisphere’s is > twofold than the right The right hemisphere is > threefold than the left Approximately 17% of adults show asymmetry of > 20% and only 1.5% > 50%. Frequency • Consistent Focal slowing of alpha rhythm by 1 Hz or more on one side • More important than voltage attenuation of alpha rhythm • The side with the lower frequency is abnormal
- 10. Conti… Reactivity Failure ofthe alpha rhythm to block either unilaterally or bilaterally is due to a structural abnormality Absence of blocking bilaterally may be due to an occipital or a pontine lesion Unilateral blocking is absent the lesion is within occipital lobe or its subcortical gray matter Photic response Asymmetric photic drive response if any structural lesion in the occipital lobe
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- 13. Abnormalities beta activity High voltage or plentiful beta activity is the most frequently encountered abnormality of fast activity in the EEG which is generalized Possible pathology Beta activity –high voltage (asymmetric& beta during sleep) Asymmetry /Focal Frequency Earliest and most sensitive for focal cortical dysfunction (B slowing) Toxic/Metabolic , Cerebrovascular accident , Seizure , Brain tumor Voltage Amplitude varies more than 35% is considered abnormal
- 14. Excessive beta activity/Generalized beta activity
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- 16. Focal slowing • SuggestsFocal cerebral dysfunction • Theta Slowing /delta slowing • Theta slowing indicate a less severe abnormality than delta slowing • Theta slowing commonly occurs together with delta slowing • Any focal delta is always abnormal • Intermittent / continuous ,Polymorphic / Monomorphic • PDA & RDA are common focal slowing
- 17. Conti… • PDA: Arrhythmicdelta wave activity (<4) with constantly changing of morphology, frequency, and voltage. • Permanent structural or a transient disturbance in the area of subcortical white matter or thalamic nuclei . • PDA is one of the most reliable findings of a focal cerebral disturbance • PDA can occur without demonstration of lesion in the MRI • Deeper lesions cause hemispheric or even bilateral distribution
- 18. Conti…. Lower voltage ofPDA is seen over the area of maximal cerebral involvement Delta from lesions in the frontal lobe is commonly volume –conducted to the opposite frontal lobe, where the delta appears, but with reduced amplitude Combination of Rhythmic delta activity and continuous focal PDA is the classic EEG sign of impending cerebral herniation Focal spike or sharp waves do not arise within a structural lesion but at the periphery where cortical structures are affected but not destroyed.
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- 20. Conti…. RDA -Deltawaves which occur in bilateral, symmetrical, bi-synchronous patterns that are rhythmical and monomorphic Commonly, they occur intermittently (burst) in runs lasting a few seconds They can be predominant, FIRDA , OIRDA ,TIRDA , Generalized RDA is activated by hyperventilation and drowsiness RDA is attenuated with sleep/ state of coma
- 21. Conti… • FIRDA andOIRDA is that these abnormal patterns do not suggest a specific localization • FIRDA/OIRDA either can be associated with anterior or posterior brain abnormalities • Location of the IRDA tells us more about the age of the patient than the location of the lesion • Pathophysiology - Partial dysfunction and over reactivity of thalamocortical circuit (not fully understood ) • Their presence signals some mild-to-moderate degree of encephalopathy
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- 25. TIRDA • TIRDA shouldbe considered separately from FIRDA and OIRDA. • TIRDA has been associated with temporal lobe epilepsy • TIRDA, which is usually unilateral, indicates the side of the lesion if one is present • TIRDA has localizing value. • Seen in drowsiness and light sleep
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- 27. Periodic epileptiform discharges •EEG pattern in which similar waveforms occur repetitiously at nearly regular intervals • PEDs are uncommon in routine EEGs with an overall incidence between 0.4% and 1%, common in the ICU • High amplitude(100-300uv) ,complex duration < 500ms , recurs with 0.5 -4s • The shape of the waveform is usually that of a spike or sharp wave, with or without a slow wave
- 28. Conti…. Discharge is continuous,not intermittent in nature, and occurs on a slowed or suppressed background through out the tracing . PEDs are associated with acute processes and occur transiently, typically between 2 and 20 days following the insult PEDs are generally caused by an acute destructive lesion (stroke , tumors, encephalitis) What are important differentials for ?? • ECG artifact • IEDs
- 29. Conti…. • PEDs canbe PLEDs , BIPLEDs , Multifocal ,GPD • PLEDS over one hemisphere often extend, by volume conduction, to the opposite side, but then are always bisynchronous and of lower amplitude. • PLEDs are usually associated with seizures (80–90%) ,focal seizures , neurological signs • short-interval GPDs are hypoxic-ischemic encephalopathy, toxic-metabolic, and Creutzfeldt Jacob Disease ,but long-interval GEPDs is Subacute Sclerosing Panencephalitis
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- 34. Conti… • Standard EEGis the diagnostic test of choice to provide electrophysiologic information about the presence of neurophysiologic dysfunction • Nonepileptiform abnormalities are common in hospital and ICU EEGs • Importance of EEG in Encephalopathy/coma pt • Depth and severity of the coma • Indicator of improvement or deterioration • Can suggest its specific cause
- 35. Conti… When we evaluateEEG of generalized non-epileptiform abnormalities Voltage Higher voltage slowing may mark the more affected hemisphere (equal frequency) Relationship b/n voltage & severity not straight forward Frequency Relationship in severity is straight forward Reactivity Amplitude ,rhythmicity , frequency (eye opening ,hand movement ,ET suction, tactile) Presence of Normal Sleep Elements Sleep spindle ,k complex (presence & symmetry)
- 36. Conti… Can suggestits specific cause Anoxic encephalopathy –Delta ,Periodic discharge Hepatic coma –Triphasic wave Encephalitis – Short interval PLEDs Subacute Sclerosing Panencephalitis –Long interval PLEDs
- 37. EEG pattern indiffuse nonepileptiform abnormalities Generalized slowing Triphasic Waves (TWs) Rhythmic coma pattern Generalized Periodic discharge Burst-suppression pattern Voltage attenuation/Suppression Electrocerebral inactivity (ECI)
- 38. Generalized slowing • Generalizeddelta activity outside of (Sleep, posterior slow waves of youth, and hyperventilation)is always abnormal • Generalized PDA/RDA indicates a non-specific, generalized dysfunction, which may be reversible or irreversible • Generalized PDA are regarded as a sign of supra-tentorial white matter abnormality • Generalized abnormality may be due to a wide variety of causes, including metabolic, toxic, anoxic and degenerative process.
- 39. Conti… RDA Mild tomoderate degree of encephalopathy Associated with diff use gray matter disease Reactive to external stimuli Generalized RDA is rare PDA Severe diffuse encephalopathy Nonreactive to external stimuli. White matter is always involved ,but cortical origin
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- 41. Triphasic Waves Triphasicwaves is almost always associated with a state of depressed consciousness Triphasic waves are usually caused by a metabolic derangement Triphasic pattern, often with a sequence of negative–positive–negative deflections Triphasic waves usually occur diffusely and symmetrically, often with a frontal predominance Anterior-to-posterior time lag in which the wave is seen frontally up to 200 ms before it is seen posteriorly
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- 43. Rhythmic coma pattern •Invariant, nonreactive, diffuse cortical activity of a specific frequency, such as alpha, beta, spindle, or theta, is called “rhythmic coma.” even rhythmic delta (discussed) • Pathogenesis behind is relative normal function in the rhythm generators (Diencephalon) • Alpha patterns in alpha coma are more diffuse and continuous. • Spindle coma can be distinguished from alpha coma in , in spindle coma each spindle has a discrete duration and spindles should be maximally expressed in the frontocentral regions • Some cases of Rhythmic coma with poor outcome may be explained by patterns of damage that involve brainstem structures
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- 47. Burst-Suppression Pattern Burst-suppression patternsconsist of periodic bursts of polymorphic activity, often containing sharp features, separated by periods of voltage suppression Pattern characterized by paroxysmal bursts of theta and/or delta waves, at times intermixed with sharp and faster waves, alternating with intervening periods of attenuation or suppression (below 10 mV) lasting more than 50% of the record. In a minority of patients, a myoclonic movement may accompany each burst Lower voltage bursts and longer and flatter interburst intervals correlate with increasing severity B-S can be intermittent/continuous , variations in the frequency and duration of bursts and suppressed periods
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- 50. Voltage Suppression • Suppression:Entirety of an EEG record showing activity below 10 mV (reference derivation) > 99 % of the tracing • Continued deterioration of a burst-suppression pattern in which the bursts have disappeared leaving only the periods of suppression • Very short tracings are inadequate to establish a diagnosis of voltage depression
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- 52. Electrocerebral inactivity (ECI) Electrocerebral inactivity is defined as a complete lack of EEG activity over 2 V when the following appropriate recording techniques are used A complete set of scalp electrodes should be used, including the midline electrodes Inter-electrode impedances should be less than 10 000 Ohms and more than 100 Ohms. The integrity of the entire recording system should be checked The montage used should employ electrode pairs more than 10 cm apart ) Sensitivity must be increased to 2 uV/mm for at least 30 minutes of recording.
- 53. Conti…. Appropriate filter settingse.g. LFF 1.0 Hz, HFF not below 30 Hz. Additional monitoring may be needed to identify artefacts e.g. ECG, limb electrode for movement. There should be no EEG reactivity to intense tactile, visual or auditory stimuli. Recording performed by a qualified EEG technologist. When ECI in doubt, repeat study should be performed
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- 55. Reference • PRACTICAL APPROACHTO EEG 3rd edition • Rowan’s PRIMER of EEG 2nd edition • Atlas of Electroencephalography 3rd edition • Atlas of EEG Patterns 3rd edition • Study EEG online
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Editor's Notes
- #4 EEG is the diagnostic test of choice to provide electrophysiologic information about the presence of neurophysiologic dysfunction
- #5 Non- epileptiform abnormalities include diffuse slowing in encephalopathy and focal slowing with a structural brain lesion involving the white matter tracts Non-epileptiform abnormalities are associated with transitory or permanent dysfunction but not with an increased risk of seizures
- #6 The EEG is a poorly sensitive and specific test to detect structural brain lesions compared to advanced imaging (MRI) theta slowing indicate a less severe abnormality than delta slowing Abnormality below the midbrain/upper pons does not result in EEG abnormality presence of reactivity to a stimulus indicates a less severe encephalopathy as compared to a lack of reactivity Increasing dysfunction, and the loss of functioning neurones, decreasing amplitude
- #7 , but because the specificity is low, a broad differential is required. To say pattern there should be 6 cycles
- #8 always important to choose an appropriate referential montage
- #9 Posterior rhythm – awake ,alpha range ,high voltage(40-60) ,sinusoidal ,during eye closure ,attenuates during (eye opening ,fixation ,visual cognition ) ,never be in the frontopolar area . Rt posterior rhythm –has higher amplitude b/c of non-dominant area ,but does not exceed 20 percent alpha rhythm is not present in up to 10% of healthy individuals (childhood blindness ,genetic) Hypothyroidism and antiepileptic medications decrease alpha frequency Consistent focal slowing of alpha rhythm by 1 Hz or more on one side reliably identifies the side of focal abnormality whether the voltage of the rhythm is increased or decreased
- #10 (Bancaud’s phenomenon absence of the posterior rhythm should be considered normal ,if no associated abnormality is there Photic drive mean synchronization with light frequency
- #11 R1 –failure of alpha blocking (left) for eye opening ,7 yrs old P1 -asymmetric photic response with lower amplitude and less reactivity in the left compared to the right hemispheres(structural /epileptic focus on less response).6 yrs old
- #12 secondary bilateral synchrony with lateralized epileptic focus in the right hemisphere , attenuation of alpha rhythm in the right hemisphere. , 6-year-old boy with intractable symptomatic absence epilepsy ,thalamus heterotopia
- #13 Normal beta activity – 13-30hz , not the predominant frequency band ,amplitude < 20uv , Common cause of excess fast activity in the waking EEG is pharmacologic effect (Benzodiazepines , barbiturates) Drug related increases in beta activity are usually diffuse but may also be frontally predominant increased fast activity is common in developmental delay or mental retardation
- #14 This tracing- high amplitude beta activity (18-23hz more on anterior electrode) ,on clonazepam Asymmetric, generalized beta activity can indicate abnormality. Normally – B wave is less than 20 μV Generalized beta activity usually is symmetric to within a 35% difference in amplitude ,predominant rhythm benzodiazepines and barbiturates , Hypothyroidism , neuroleptics, phenytoin, anxiety ( cocaine, amphetamine & TCA -GBA ) Lissencephaly-Pachygyria , mental retardation –excessive beta When beta activity is predominant, the term generalized beta activity applies
- #15 Mild lesion on left frontotemporal 9 yr old left side stroke (encephalomalacia) shows attenuation of beta activity (arrows) in the left frontal-temporal region , Suppression of anterior beta activity is usually more sensitive than focal polymorphic delta activity in determining structural abnormality
- #16 Look for - Frequency ,Amplitude ,Persistence ,Symmetry ,Reactivity ,Rhythmicity ,Location Focal /generalized Normal theta – emotional ,older ,drowsiness ,REM sleep Not all theta and delta waves are abnormal ,any focal delta and generalized delta activity (except -HV , Sleep & young age) always abnormal
- #17 Normal PDA is a characteristic finding of nonrapid eye movement (NREM) sleep focal depression of beta activity is earlier & more sensitive Abnormality confined to the cortex does not produce slowing Abnormality below the midbrain/upper pons does not result in EEG abnormality Cortical lesion less likely to result slowing rather white matter involvement
- #18 The more persistent, the less reactive, and irregular of the PDA, the more reliable as indicator it becomes for the presence of a focal cerebral disturbance Possible Mechanisms Interruption of the afferent input to the cortex Dorsal thalamus produces intrinsic 1–2 cycles/s
- #19 P1 -EEG of a 12-year-old girl with exacerbation of migraine ,There is background slow activity with the main posterior activity of 5–6 Hz. In addition, polymorphic delta activity maximally expressed in the left temporal region is noted. EEGs vary from normal to mildly abnormal (loss of alpha rhythm, intermittent focal delta activity) during visual auras and common migraine P3 -45-year-old ,left side slowing polymorphic ,postictal ,resolved after 1month EEG P4 -an asymmetry of slow activity with increased theta waves on the left as a result of an old perinatal injury to the left temporal lobe tip in a 17-year-old girl.
- #20 associated with processes of mild to moderate severity RDA is a pattern typically seen in wakefulness , not during deep sleep & coma FIRDA is rarely reported to be associated with generalized epilepsy
- #21 independence of the lesion locations, which may be at some distance occipital intermittent rhythmic delta activity is seen in children with childhood absence epilepsy FIRDA is usually seen in adult Both has similar significance FIRDA appears frontally, the finding does not necessarily imply a frontal pathology
- #22 FIRDA1 -rhythmic runs of delta activity in the frontal areas of varying duration FIRDA 2- on theta background RIRDA3 -Asymmetric FIRDA ,better developed on the left FIRDA4 -Rhythmic delta ,sharp wave superimposed
- #23 1 , OIRDA –fast activity (lorazepam) ,ICU ,9-year-old , suggestive of mild encephalopathy 2 , OIRDA – bi-synchronous ,3 hz , high voltage , rhythmic delta , 12 year ,on dialysis 3 OIRDA –HV , bilateral occipital delta ,3 hz spike & wave pattern –absence epilepsy
- #25 , highly pathognomonic for temporal lobe epilepsy, especially caused by mesial temporal sclerosis.
- #26 TIRDA – Over the right temporal area ,extending to rt parasagittal electrode TIRDA2 -TIRDA) is seen in a patient with temporal lobe epilepsy ,this rhythmic delta activity is seen best in the left temporal area extending to parasagittal area
- #27 inter-ictal epileptiform discharge discussed earlier, which does not occur in nearly regular intervals,
- #28 evolve and abate over an average 2-week time , widespread cortical processes , An acute structural lesion was evident in 71% Seventy-three percent of children found to have PLEDs on continuous EEG monitoring in the ICU experienced NCSE , BiPLED group, where the mortality rate was 52% PLEDs usually are not nearly as regular in their interval as ECG artifact , ECG artifact usually is maximal in the temporal regions IEDs – Less regular , if regular prolonged inter discharge interval Cortical stroke is responsible for almost half of the incidence of PLEDs, and tumors and infections are each responsible for almost another 20%
- #29 short-interval (0.5 – 4.0 sec) or long-interval (4.0 – 30.0 sec) types
- #30 PLED 1- 65-year-old ,0.5 -1 hz ,frontopolar ,lateralized (rt) ,diphasic /triphasic discharges –after clipping RT MCA /SAH PLED 2 – left side 1hz ,high amplitude ,repetitive ,sharp & rounded apex
- #31 BIPEDS –75-year-old ,bitemporal independent ,periodic discharge ,post anoxic Seizure is less common (30%) but death is 60%
- #32 GPD 1-44-year-old .post cardiac arrest GPA 2 -maximal in the bilateral central regions, Low ,amplitude slow background activity ,highly regular, monophasic to polyphasic
- #34 a deteriorating neurological status, a parallel deterioration in the EEG is expected EEG can serve as a useful adjunct to the clinical examination EEG plays a special role in ascertaining the depth of coma pharmacologically paralyzed , EEG may be the principal source of information regarding the patient’s neurologic state EEG patterns are dictated more by the function of the cerebrum than the brainstem
- #35 While decreased voltage amplitude on the EEG typically correlates with increasing severity of encephalopathy, high-amplitude activity can still occur in certain conditions, especially when there is significant disorganization, toxicity, or postictal effects. The commonest EEG features of sleep – slow wave ,& sleep spindle most severe patterns can have a good fi nal outcome
- #36 B-S pattern or electrocerebral silence (ECS) does not carry as ominous prognosis as when they occur in the setting of cardiopulmonary resuscitation EEG patterns such as burst suppression, voltage depression, or even “fl at” EEG patterns –over dose case Severity & prognosis mainly depends on the cause but the pattern can also affect
- #38 Normal theta – older ,small amplitude ,temporal ,asymptomatic , Abnormal theta –high amplitude , greater persistence, slower frequency ,lateralized ,adult The first sigh of encephalopathy is loss of beta activity clearing of slow-wave activity often lags behind the patient’s clinical improvement decrease in slow-wave amplitude can be associated with either improvement or deterioration in neurologic status as described earlier
- #39 A defect in cholinergic pathways may play a role in pathological slow waves Bilateral mesencephalic reticular formation and bilateral hypothalamic lesions in cats produce continuous PDA Ipsilateral IRDA is not only associated with an ipsilateral deep lesion but also can be contralateral to the focal lesion
- #40 S1 -this burst of intermittent rhythmic slow (arrow) has a more diffuse (rather than frontal) distribution. It is seen equally well in the anterior and posterior channels. S2 -Generalized poly morphic delta S3 -comatose patient , asymmetric slowing , higher voltages over the left hemisphere compared with the right , fewer theta rhythms are seen over the lower voltage right hemisphere, suggesting that this side may be more severely affected
- #41 Hepatic ,renal ,anoxic injury
- #42 TW -28-year-old man with hepatic encephalopathy , moderate amplitude ,2hz ,preceded & followed by negative wave ,AP lag ,predominant on anterior Associated with ammonia Organ failure Toxicity (gabapentin ,lithium)
- #43 Rythic delta <Spindle Coma<Continuous delta<<<< Drugs , anoxic ,metabolic associated with rhythmic coma
- #44 , 10-year-old boy with pontine stroke- Note broadly diff use distribution of alpha activity without an anterior-posterior gradient that is nonreactive to external stimuli. This EEG pattern is called “alpha coma (AC)
- #45 A 9-year-old boy with NCSE who received midazolam infusion. EEG shows anteriorly predominant theta activity intermixed with delta and beta activity. The patient was recovering after the treatment. Alpha or theta coma can also be seen in toxic encephalopathy. The EEG pattern is very similar to that seen with cardiorespiratory arrest, except that there is superimposed beta activity.62–64 Overdoses of many diff erent drugs can produce this pattern.3 The outcome depends on the underlying causes. The prognosis of alpha-theta rhythmic coma as well as of other rhythmic coma is better in children than in adults
- #46 Asymmetric Spindle Coma-A 6-year-old girl , left MCA stroke and small ischemia in the right occipital region , asymmetric 10- to 11-Hz spindle-like activity with suppression in the left hemisphere. Anterior predominance of spindle activity is noted. This fi nding is consistent with asymmetric spindle coma
- #47 Burst-suppression patterns have been associated with anoxic injury and are generally associated with a poor prognosis for neurologic recovery. in infants and children, and especially in the minority of patients in whom the pattern improves promptly, outcome may be somewhat better reactive burst suppression) are probably associated with a better prognosis than the pure form of the pattern
- #48 A group of waves with a minimum of four phases and duration longer than 500 ms which appear and disappear abruptly and are distinguished from background activity by differences in frequency, form and/or amplitude
- #49 B-S1 pentobarbital coma - B-S pattern is a complex wave form alternating with complete attenuated background activity (<10uv ) B-S2 –poly mophic ,high voltage ,burst -suppression
- #50 A low voltage EEG is defined as one with no waveforms consistently over 20mV in amplitude In children, this is abnormal, but in adults, increasingly with age, it may occur in up to 10% of normal persons Pathology associated with a generalized low voltage includes hypothyroidism, Huntington disease Paget’s disease of the skull, hypoglycemia and hypoxia, and focal low voltage may occur with scalp oedema or a subdural hematoma
- #51 S1 -This EEG of a comatose patient is displayed at a sensitivity of 7 V/mm and appears flat. Especially when electrocerebral inactivity is suspected, sensitivities of 2 V/mm should be used S2 -same page of EEG is displayed at a sensitivity of 2 V/mm, a small amount of definite electrocerebral activity is seen over the right hemisphere (bottom eight EEG channels). No electrocerebral activity is seen over the left hemisphere and midline, however. Pulsation artifact is seen in the channels that include O1
- #52 An increased distance will increase the chance of finding a small discharge. Tracings of electrocerebral inactivity should be clearly distinguished from low voltage EEGs Absence over all regions of the head of identifiable electrical activity of cerebral origin, whether spontaneous or induced by physiological stimuli or pharmacological agents. Comment: strict technical recording standards should be observed in suspected cerebral death
- #53 Electrode impedance above 10k begin to introduce more noise or artifacts into the EEG recording Tapping- confirming the presence of the tapping artifact on the recording Greater interelectrode distances increase the chance of detecting low-voltage activity.
- #54 EEG is displayed at 2 V/mm and shows electrocerebral activity (ECI) , none of the waves seen are of cerebral origin ,this tracings are prone to prone to large amounts of artifact , several channels show pulsation EKG artifact.