3. Wicket waves
• Short runs of 6-11Hz spikes, sometimes single spike
– usually within alpha frequency range
• Monophasic arciform waveforms (60-200uV)
• Anterior or mid-temporal region
– Usually unilaterally,shifting emphasis between sides
• Sharp monophasic, no slow wave
• Present in relaxed wakefulness, drowsiness, light sleep
• Usually in middle and late adulthood
• Clinical significance: analogue of the auditory alpha rhythm
– May decrease with auditory stimulation
– Not associated with epilepsy
4.
5. Benign Sporadic Sleep Spikes
BETS–Benign Epileptiform Transients of Sleep
• Occur in light sleep (non-REM 1 and 2 sleep)
• Amplitude of <50 microV and duration of <50 ms
• Usually monophasic, occasionally diphasic
• Located temporal uni- or bilateral
• Incidence of 20%
• Small sharp spikes are not associated with epilepsy
6.
7. 6 per second spike-waves
(Phantom Spike and Wave)
• Brief bursts of low amplitude spike-and-slow wave 6Hz (5-
7Hz)
• Spike often not clearly discernible: “phantom”
• Bilateral and synchronous
• Maximal at midline (posterior or anterior)
• Relaxed wakefulness and drowsiness
• Adolescents and young adults
• Duration of 1-2 seconds
8.
9. 14 & 6 Hz positive spikes
• Bursts of 14Hz (13-17) or 6Hz (5-7)
• Duration: 0.5-1 second
• Unilateral (R>L) or bilateral asynchronous or synchronous
• Arch-shaped waves / Positive sharp peaks
• Maximum in posterior temporal region
• Present in drowsiness and light sleep
• Young adults
10.
11. Rhythmic Temporal Theta of Drowsiness
(Psychomotor Variant)
• Trains of rhythmic theta waves 5-7Hz
• Duration 5-10sec
• Located in midtemporal region
• Often unilateral
• May be bisynchronous, with shifting asymmetry between sides
• Present in relaxed wakefulness and drowsiness
• Adolescents and adults
12.
13. Subclinical Rhythmic Electrographic
Discharge of Adults (SREDA)
• Abrupt onset and termination of sharp rhythmic theta rhythm of
5-7Hz
• Constant frequency
• Duration of 40-80 sec
• Located Parietal and Posterior temporal
• Bilateral and synchronous, symmetrical (however sometimes
unilateral)
• No change in localization of frequency
• Present in wakefulness, drowsiness, stage II sleep
• Trigger: Hyperventilation
• Usually in people >50 years
• Uncommon (incidence <0.05%)
14.
15. POSTS(Positive Occipital Sharp
Transients of Sleep)
• Located in the occipital regions bilaterally as positive waves, during
drowsiness/sleep
• Triangular in shape (like the capital lambda: Λ, only upside down) and
generally symmetric.
• Most evident in non-REM 1 and non-REM 2
• Amplitude 20 - 75 μV and may be as high as 120 μV, duration 80 to
200 ms
• Same morphology as Lambda waves, both in form and in occipital
distribution(lambda waves are during awake state, when visually
fixating).
• POSTS are completely normal, should not be confused with spikes
16.
17. Lambda
• Located in the occipital regions bilaterally as positive
waves.
• Triangular in shape (like the capital lambda: Λ) and
generally symmetric.
• Amplitude: 50 microV
• Duration 200-300 msec
• Present with eyes opened and during visual fixation
• Same morphology as POSTS (Positive occipital sharp
transients of sleep), both in form and in occipital
distribution, however POSTS are during sleep.
18.
19. MU
• Frequency: 8-12 Hz
• More sharply than Alpha rhythm
• Most prominent in central regions
• Frequency asymmetry of >1 Hz is abnormal
• Mu rhythm is suppressed by contralateral opening and closing
of the fist.
20.
21. Vertex sharp wave
• Generally diphasic ,sharply contoured.
• Maximum amplitude at C3 & C4 lasting upto 200 ms.
• Initial deflection surface negative f/b slower & lower voltage positive
wave.
• Maximum at the vertex (like K complex)
• Amplitude: 50-150 microV
• Presence in non-REM 1 and to a lesser extent in non-REM 2
• Narrower and more focal than K complex
• Unlike K complex vertex waves are not associated with sleep spindles
.
22.
23. K Complex & Sleep Spindle
• Presence in Non-REM 2 sleep
• High amplitude (>100 microV)
• Long duration (>200ms)
• Diphasic
• Broad field that phase reverses in the vertex region.
• Often associated with sleep spindles
• Location: Frontocentral with the maximum at Cz or Fz.
24.
25. Alpha variants
• Appears in the occipital regions at a frequency onehalf that of the
ongoing PDR
• Suspect its presence when PDR activity has a notched appearance,
revealing its subharmonic relationship
• Slow alpha variant has the same characteristics as the PDR itself – for
example, it attenuates with eye opening.
• Fast alpha variant also appears in the occipital areas and has a
frequency twice that of the PDR.
• These variants may alternate with the PDR, or the PDR may not
be present at all
26.
27. Posterior slow wave of youth
• Occur amid the alpha rhythm (AR) and are evident because of their
longer wave duration.
• Have a posterior field ,maximal at the occipital poles, present only
in relaxed wakeful states with eyes closed.
• Evident with bipolar montages, sometimes better seen with longer
interelectrode distances.
• Occipital and central electrodes depict PSWY well
• The wave polarity is inconsistent and the wave duration typically
ranges from 0.3 to 0.5 seconds
• Most commonly, PSWY appear as sporadic, interspersed slow waves
• PSWY usually are symmetric and bisynchronous across the
occiput but may occur with minor lateralization, which is typically
toward the right
28.
29. Mittens
• Produced through the partial superimposition of a sharp wave on
the up slope of a following slow wave of the same polarity.
• Overlap produces a notching in the slow wave that divides the
slow wave into two compartments, which are a smaller and sharper
thumb compartment, and then a larger and rounder hand
compartment
• Centered in the frontal-central midline with extension into the
parasagittal regions bilaterally and possible inclusion of the parietal
region also.
• The duration - 400 to 500 ms and amplitude is high.
• The pattern emerges out of anterior, polymorphic delta activity of
deep sleep.
30.
31. Frontal arousal rhythm
• Trains of 7- 10Hz monomorphic, symmetrical waveforms
• Duration: <20sec
• Localisation: Frontal regions.
• Occurs in children following arousal from sleep
• Disappears once child is fully awake
• NOT to be confused with frontal arousal rhythm in the theta
range described by Hughes
32. The 7-Hz Cigánek rhythm is sustained through the first three occurrences of eye blink artifact and then ends
with the fourth eye blink and increase in muscle artifact. The combination of eye blink and increased muscle
artifact indicates an increase in wakefulness, which is a state change that can diminish a Cigánek rhythm.
33. Midline theta rhythm(Ciganek)
• Rhythmic train of 5-7Hz (6Hz)
• Duration: <20sec
• Smooth, sinusoidal, arch-like, spiky appearance (>50uV)
• Amplitude waxes and wanes
• Vertex (Cz)
– Fz > Pz >> parasagittal electrodes
• Wakefulness (concentration) and drowsiness
• Children and adults
• Not associated with epilepsy
34. References
• Rowan’s PRIMER of EEG,Second Edition
• Atlas of EEG Patterns (Stern&Engel),Second
Edition, LIPPINCOTT WILLIAMS & WILKINS
