Distictive features of transition to Stage 1 Sleep (4)
- Slowing and anterior spread of alpha activity follow by
- Dropout of the posterior dominant rythym
- Slow lateral eye movements seen in the lateral eye and frontal leads
- Vertex sharp waves
Eye-Ball Polarity
Cornea positive/Retina Negative
Dropout of posterior dominant rythym in Stage 1 sleep is replaced by…
- disorganized low amplitude mixture of frequencies
- theta activity predominating
Vertex sharp waves (sign of late drowsiness) of stage 1 sleep are characterized by (amplitude, distrubution, morphology, duration)…
maximal amplitude (referential montages) and reverse phase (bipolar montage) at the Cz electrode
- monophasic
- surface negative
- lasting 70-200ms, with highly variable amplitude
Hypnogogic Hypersynchrony of children and adolescents may be associated with (frequency, amplitude)…
theta to delta frequency slowing (usually around 4Hz) with amplitudes as high as 300microV - NOTE: if seen with spike like features, only consider generalized epilepsy if occurs in other than drowsy states.
Distictive features of transition to Stage 2 Sleep (2)
- K complexes
- sleep spindles
K complexes of Stage 2 Sleep are characterized by (amplitude, distribution, duration)…
- high amplitude
- diffuse to centrally predominant biphasic slow wave transients
- last 0.5s
- at least 75microV
Sleep Spindles of Stage 2 Sleep are characterized by (morphology, frequency, amplitude, distrubution, duration, synchrony…
- sinusoidal or spindle shaped (pointy at the ends
- 12-14Hz
- low amplitude
- frontal to centrally
- typically lasting 1-3 seconds
- may occur asymmetrically but should overall be same amount on both sides
The initial phase/deflection of a K-complex is..
Negative/Upward
Besides Stage 2 sleep, K-complexes can be observed in
Brief Partial Arousals. e.g. can be demonstrated by lightly tapping pen on table during stage 2 sleep
The defining waveform for Stage 2 sleep
Sleep Spindles
Stage of Sleep associated with increased interictal epileptiform activity (reason sleep deprived EEG are ordered)
Stage 2
Distictive features of transition to Stage 3 Sleep (aka. Slow Wave Sleep) (1/N)
-20% of the activity on a 30 second EEG recording is delta frequency
NOTE: delta of sleep requires a minimum of 2Hz or less (rather than 4Hz) and at least 75microV using a contralateral referential ear montage
Distictive features of transition to REM Sleep (4)
- Rapid Eye Movements
- Low Amplitude (voltage)
- Mixed Frequency
- Low Amplitude EMG at the chin
Posterior Occipital Sharp Transients of Sleep (POSTS) can occur in which stage of sleep?
Stages 1 or 2
Posterior Occipital Sharp Transients of Sleep (POSTS) are characterzied by (morphology, distribution, frequency, rythmicity, synchrony
- surface-positive monophasic
- occipital distribution
- 4-5Hz
- arrythmic
Arousal pattern from Stage 1 sleep is characterized by…
return of the alpha PDR
Arousal pattern from Stage 2 or deeper sleep is characterized by (amplitude, morphology, duration…
- high amplitude
- biphasic or triphasic
- lasts 0.5 sec or longer
Activating Procedures are used to…
influence EEG activity that may reveal abnormalities that would not be seen otherwise
What are the types of Activating Procedures (5)
- Mental Alerting
- Hyperventilation
- Sleep
- Eye Opending/Closure
- Photic Stimulation
How is Mental Alerting used as an activating procedure?
Used to distinguish pathological vs. state-dependent slowing of the PDR. e.g. calling name, counting 1-10, serial subtractions, spelling WORLD backwards
How is Hyperventilation used as an activating procedure?
mechanism underlying changes in activity controversial; after 30-60sec theta slowing of PDR, with diffuse rythmic polymorphic activity theta range; continued hyperventilation may result in dramatically increased amplitude (several hundred microV) and further slowing to delta frequency (HIHARS/”buildup”
How is Sleep used as an activating procedure?
- Accomplished through behavioral techniques such as sleep deprivation. Must achieve Stage 2 sleep.
- Activating for nearly all forms of epilepsy but notably in electrical status epilepticus of sleep, benign childhood epilepsy with centrotemporal spikes, juvenile myoclonic epilespsy,
How is Eye opening and closure used as an activating procedure?
Eye opening blocks the PDR, Eye closure results in return of the PDR with faster frequency in first seconds after eye closure (aka “squeak”)
NOTE: in children with childhood epilepsy with occipital paroxysms (CEOM), the occipital spikes are sometimes suppressed by eye opening.
How is Photic Stimulation used as an activating procedure?
Each strobe flash causes excitatory potential generated in the striate cortex (same waveform that occurs 100ms after VEP stimulus), best frequency varies for all individuals but is probably a harmonic of native PDR, absence of response is only abnormal if asymmetrical
HIHARS
Hyperventilation-Induced High-Amplitude Rythmic Slowing
What are the contraindications to Hyperventilation as an activating procedures? (5)
- COPD or other chronic lung disease
- pregnancy
- recent stroke or SAH
- sickle cell disease
- moyamoya disease
How can the photomyoclonic response or photoelectric response confuse photic stimulation results?
- photomyoclonic response results from stimuli-induced eye blinking or facial twitching and is seen in frontal electrodes
- photoelectric response results in activation of an electrical impulse of the frontal electrodes (RARE)