The document provides information about EEGs and EMGs. It defines EEG as recording electrical activity of the brain from the scalp and notes its history and applications in diagnosing conditions like epilepsy. It describes different brain waves seen in EEGs including alpha, beta, theta, and delta waves and their characteristics. It also summarizes sleep cycles and brain waves associated with each stage of sleep. The document then discusses EMG and how it records muscle activity through motor units. It notes the techniques of surface EMG and intramuscular EMG and what abnormalities in spontaneous activity or motor unit potentials can indicate.

1. EEG/EMG
DR.RAJEEV BHANDARI
NATIONAL ACADEMY OF MEDICAL
SCIENCES
BIR HOSPITAL

2. DEFINITION:-
• The electroencephalogram (EEG) is a recording of
the electrical activity of the brain from the scalp.

3. History
Richard Caton (1875) –localization of sensory
functions with monkeys and rabbits
Hans Berger (1924) – first EEG recording done on
humans
described alpha wave rhythm and its suppression
compared to beta waves
acknowledged “alpha blockade” when subject opens
eyes
William Grey Walter –delta waves during sleep
(1937) and theta waves (1953)

4. Terminology
• The international 10-20 system is used
• Four area identified
• Odd number on left side
• Even number on right side
• Lower numbers closure to midline
• Midline Z= Zero

5. Terminology
• Two differential amplifier used
• Consists of bipolar and unipolar montages
• First-left Temporal chain
• 2nd – left Parasagittal chain
• 3rd - midline
• 4th- right Parasagittal chain
• 5th- right Temporal chain
• 6th – Single EKG channel
Output

6. APPLICATION
A1-left ear A2-right ear
Fp-frontal pole leads
F-frontal leads
P-parietal leads
C-central leads
T-temporal leads
O-occipital leads

7. Nasopharyngeal
Temporal
Auricular
Occipital
Left Right

8. Factor influencing EEG
• Age
– Infancy – theta, delta wave
– Child – alpha formation.
– Adult – all four waves.
• Level of consciousness (sleep)
• Hypocapnia(hyperventilation) slow & high amplitude
waves.
• Hypoglycemia
• Hypothermia
• Low glucocorticoids
Slow waves

9. INTERPRETATIONS
Alpha Wave
• Characteristics:
– frequency: 8-13 Hz
– amplitude: 10-200 μV
• Easily produced when quietly sitting in relaxed
position with eyes closed (few people have trouble
producing alpha waves)
• Alpha blockade occurs with mental activity

10. Beta Waves
• Characteristics:
• frequency: 14-30 Hz
• amplitude: 1-20 μV
• The most common form of brain waves. Are
present during mental thought and activity

11. Theta Waves
• Characteristics:
– frequency: 4-7Hz
– amplitude: >50μV
• Believed to be more common in children than
adults
• Walter Study (1952) found these waves to be
related to displeasure,pleasure, and drowsiness
• Maulsby (1971) found theta waves with amplitudes
of 100μV in babies feeding

12. Delta Waves
• Characteristics:
– frequency: 0.5-3Hz
– amplitude: >50 μV
• Found during periods of deep sleep in most people
• Characterized by very irregular and slow wave
patterns
• Also useful in detecting tumors and abnormal
brain behaviors

13. Gamma Waves
• Characteristics:
– frequency: >30 Hz
– amplitude: 3-5μV
• Occur with sudden sensory stimuli

14. Different types of brain waves in EEG
Waves Frequency Amplitude(μV) Mental status, level of consciousness
Delta (δ) 0.5-3 >50 Pathological status
Children in sleep
Theta(θ) 4-7 >50 Children, drowsy adult,
emotional distress
Occipital,Temporal
Alpha(α) 8-13 10-200 Adults, rest, eyes closed.
Occipital region
Beta(β) 14-30 1-20 Attention,Concentration, Frontal region
Gamma >30 1-20 Attention, Concentration, Cortical area

15. Less Common Waves
• Kappa Waves:
– frequency: 10Hz
– occurred in 30% of subjects while thinking in Kennedy et
al.(1948)
• Lambda Waves:
– amplitude: 20-50μV
– last 250 msec, related to response of shifting visual image
– triangular in shape
• Mu Waves:
– frequency: 8-13Hz
– sharp peeks with rounded negative portions (7% of
population)

16. Different stages of sleep and their respective brain waves:
• Stage 1: Low voltage random EEG activity (2-7 Hz)
• Stage 2: Irregular EEG pattern/negative-positive spikes (12- to 14- Hz)
– Also characterized with sleep spindle and K-complexes that could occur every
few seconds.
• Stage 3: Alternative fast activity, low/high voltage waves and high amplitude
delta waves or slow waves (2 Hz or less).
• Stage 4: Delta waves
• Stage REM (Rapid eye Movement): “episodic rapid eye movements,” low
voltage activity.
• Stage NREM: All stage combined, but not including REM or stages that may
contain REM.
• The K-complex occurs randomly in stage 2 and stage 3
• The K complex is like an awaken state of mind in that is associated with a
response to a stimulus that one would experience while awake

17. EEG brain waves in the Sleep Cycle:

20. Diagnostic Yield of Epilepsy
• Likelihood of finding epileptiform discharge
Single EEG within 24 hrs 50%
Single EEG after 24 hrs 20-50%
24 hours EEG recording 80-90%
4 or more routine EEG 80-90%

21. Determinants on EEG recording
• Area of cortex involved
» Small area involved might not picked up by overlying electrode-
10-20cm2 of cortex
• Location:-
• Cingulate Gyrus
• Mesial Temporal area
• Insular Gyrus

22. Desynchronization or Alpha block
Cause:-
Eyes opening (after closure)
Thinking by the subject(Mathematical Calculation)
Sound (clapping)

23. Eye opening
• Alpha rhythm changes to beta on eye opening
(desynchronization / α- block)

24. Thinking
• Beta waves are observed

25. Provocation test
• Intermittent photic stimulation
– Increase rate & decrease amplitude
• Hyperventilation
– Decrease rate & increase in amplitude

26. • Polyspikes –these rapid Polyspikes are found in
– GTCS
– Post traumatic epilepsy
– Lennox gastaut syndrome

27. Spikes and slow wave complexes typical
• 3/sec-absence seizures
• Fast - 4-6/sec-myoclonic jerks
• Sow -1-2.5/sec-intractable epilepsy with MR

31. More advanced methods of telemetry
and foramen ovale recording
– to establish the diagnosis of ‘epilepsy’ if doubt remains
– to determine the exact frequency and site of origin of the attacks
– to aid classification of seizure type.
• Telemetry: utilises a continuous 24–48 hour recording of EEG,
often combined with a videotape recording of the patient.
• Increasing availability of this and ambulatory recording has
greatly improved diagnostic accuracy and reliability of seizure
classification.
• Foramen ovale recording: a needle electrode is passed
percutaneously through the foramen ovale to record activity
from the adjacent temporal lobe.

32. EMG

33. EMG (Electromyogram)
• Bioelectric potential associated with muscle
activity .
• A motor unit is defined as one motor neuron and
all of the muscle fibers it innervates.
• When a motor unit fires, the impulse (action
potential) is carried down the motor neuron to the
muscle.
– The area where the nerve contacts the muscle is called the
neuromuscular junction, or the motor end plate.
• EMG potentials range between less than 50 μV
and up to 20 to 30 mV.

34. Electromyogram (EMG)
• Usually a summation of the individual action
potentials from the fibers consisting the muscle or
muscles being measured.
• There are two kinds of EMG in widespread use:
– 1. Surface EMG
– 2. Intramuscular (needle and fine-wire) EMG.
• Abnormal spontaneous activity might indicate
some nerve and/or muscle damage

36. • Both are essential in the investigation of diseases
of nerve (neuropathy) and muscle (myopathy).
• Repetitive nerve stimulation tests are important
in the evaluation of disorders of neuromuscular
transmission, e.g. myasthenia gravis.

37. Method
• A concentric needle electrode is inserted into muscle.
• This records from an area of 300μ radius.
• The potential difference between the two electrodes is
amplified and displayed on an oscilloscope.
• Normal muscle at rest is electrically ‘silent’ with a resting
potential of -90 mV; as the muscle gradually contracts,
motor unit potentials appear

39. Spontaneous activity at rest
Fibrillation potentials are due to single muscle fibre contraction and
indicate active denervation.
They usually occur in neurogenic disorders, e.g. neuropathy.

40. Slow negative waves preceded by sharp positive spikes. Seen in chronically denervated muscle,
e.g. motor neuron disease, but also in acute myopathy, e.g. polymyositis.
These waves probably represent injury potentials.

41. Motor unit potential

42. Interference pattern
In myopathy, recruitment of motor units and the interference pattern remain normal. The
interference pattern may even appear to increase due to fragmentation of motor units.

43. Myotonia
High frequency repetitive discharge may occur after voluntary movement.
The amplitude and frequency of the potentials wax and wane giving rise to the typical ‘dive
bomber’ sound on the audio monitor.
An abnormal myotonic discharge provoked by moving the needle electrode.

44. • Thank you!