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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
