NORMAL ADULT EEG - ACNS

NORMAL ADULT EEG&

ACTIVATION MANEUVERSIoannis Karakis, MD, PhD, MSc, FACNS

Associate Professor of NeurologyEmory University School of Medicine

CONFLICTS OF INTEREST

None

OUTLINE

Orderly approach and essential elements of visual EEG analysis

Normal EEG Wakefulness Drowsiness Sleep

Activation maneuvers Hyperventilation Photic stimulation Sleep deprivation

Conclusions

ORDERLY APPROACH TO VISUAL EEG ANALYSIS

ESSENTIAL ELEMENTS OF EEG ANALYSIS1. Frequency of wavelength

2. Voltage

3. Waveform

4. Regulation (voltage, frequency)

5. Manner of occurrence (random, serial, continuous)

6. Locus

7. Reactivity (eye opening, mental calculation, acapnia, sensory stimulation, movement, affective state)

8. Interhemispheric coherence (homologous areas)

a. Symmetry (voltage, frequency)

b. Synchrony (wave, burst)

Ebersole and Pedley, Current Practice of Clinical Electroencephalography, 3rd edition

EEG RHYTHMSRhythm Frequency Normal Examples Abnormal examples

Alpha 8-13 Hz -Waking posterior rhythm in older children and adults-Mu rhythm

-Alpha coma-Seizures in the alpha range

Beta > 13 Hz -Drowsiness in children -Drug induced-Breach rhythm-Seizures in the beta range

Theta 4-7 Hz -Drowsiness-Young children-Temporal theta in elderly

-Structural lesion-Encephalopathy-Seizures in the theta range

Delta < 4 Hz -Sleep-Posterior slow waves of youth

-Structural lesion-Encephalopathy-Seizures in the delta range

NORMAL EEG IN WAKEFULNESS AND SLEEP

POSTERIOR DOMINANT RHYTHM

2 yo

20 yo

PROMINENT ALPHA

NO ALPHA

SLOW ALPHA VARIANT

FAST ALPHA VARIANT

ALPHA SQUEAK

DROWSINESS (N1)

DROWSY HYPERSYNCHRONY

STAGE II SLEEP (N2)

POSITIVE OCCIPITAL SHARP TRANSIENTS OF SLEEP

VERTEX IN RUNS

SHARP VERTEX WAVES

VERTEX WITH SPIKES

ASYMMETRIC SPINDLES

SLOW WAVE SLEEP (N3)

RAPID EYE MOVEMENT SLEEP (REM)

WAKEFULNESS AND SLEEP STAGESStage Features

Wakefulness PDR of 8-13 Hz, desynchronized background

N1Stage 1A

Stage 1B

Reduction of muscle and eye blinking artifact, anterior widening of the field of PDR, slow horizontal eye movementsAttenuation of PDR, appearance of theta, vertex waves and POSTS may appear

N2Stage 2 Loss of PDR, sleep spindles, vertex waves and K complexes

N3Stage 3

Stage 4

More delta activity (20-50% of EEG), fewer vertex and spindles

Prominent delta (>50% of EEG), vertex waves and spindles few to none

REM Low voltage alpha/theta background with rapid eye movements

ACTIVATION MANEUVERS

HV: MINIMAL BUILD UP

HV: GOOD BUILD UP

HV: PROMINENT BUILD UP WITH STARVATION

HV: BLINKING ARTIFACT

HV: ABSENCE SEIZURE

PS: MINIMAL DRIVING

PS: VISUAL EVOKED RESPONSES

PS: GOOD DRIVING

PS: ASYMMETRIC DRIVING

PS: ELECTRORETINOGRAM

PS: PHOTOELECTRIC ARTIFACT

PHOTOMYOGENIC RESPONSE

PS: NON EPILEPTIC SEIZURE

PS: BLINKING ARTIFACT

PS: PHOTOPAROXYSMAL RESPONSE

PS: PHOTOPAROXYSMAL RESPONSE

SLEEP DEPRIVATION

Awake

Asleep

Procedure Response

Photic stimulation -VER: for frequencies <5/sec, not abnormal unless unilateral-Driving response: >7sec, most prominent at the frequency of the posterior rhythm, or at multiple thereof. Time-locked to the stimulus. Absence is not abnormal-Photomyogenic response: from frontal scalp muscles => in frontal leads, time-locked to the stimulus => stops with its end, fast (EMG) spikes w 50-60 msec delay-Photoparoxysmal response: posterior or generalized, may stop before or outlast the stimulus, slower spike-and-wave complexes, frequency independent of stimulus-Photoelectric artifact: generated by the electrode-gel-complex => mostly frontal leads, time locked to the frequency of photic stimulation-ERG: in frontal leads, generated by the retina

Hyperventilation Used predominantly to activate 3/sec spike-and-wave discharges of absence seizures. The normal response in adults is no or mild build up of theta range activity but in children the slow activity is more prominent

Sleep deprivation Particularly potent for RLE/ESES or EMGA/JME (after arousal from a brief nap following sleep deprivation)

TAKE HOME MESSAGES

CONCLUSIONS

Analysis of the EEG is a rational and systematic process

It requires characterization of essential elements of the EEG waveforms (such as their location, frequency, configuration, manner of occurrence, symmetry and synchrony) and their amalgamation to an overall EEG pattern

In that process, the basic clinical information needed is the age and state of the patient

Various activation procedures are commonly used during EEG (such as hyperventilation, photic stimulation, and sleep deprivation) to increase the diagnostic yield

Knowledge of the normal elements and activation procedures effects is paramount to differentiate them from abnormal findings and artifacts

When in doubt, increase the recorded sample, use clinical judgement and err on the side of under-calling

REFERENCES

Current Practice of Clinical Electroencephalography, John Ebersole and Timothy Pedley

Niedermeyer's Electroencephalography: Basic Principles, Clinical Applications, and Related Fields, Donald L. Schomer and Fernando Lopes da Silva

The Clinical Neurophysiology Primer, Andrew Blum and Seward Rutkove

Clinical Neurophysiology, Devon Rubin and Jasper Daube

Primer of EEG: With A Mini-Atlas, James Rowan and Eugene Tolunsky

THANK YOUQuestions?

ioannis.karakis@emory.edu