Beningn variants of EEG- DR Pallav JAIN

1. Benign variants of EEG
Dr Pallav Jain
Senior Resident
GMC,Kota

2. Characteristics of an
epileptiform discharge
Spikes and sharp waves(SSW) of cerebral origin always occupy a
definable electrical field and is seen in >2 nearby electrode sites.
Clinically significant SSW are mostly surface negative in polarity
initially, or at least the sharpest /highest voltage of the wave is usually
surface negative.
Most SSW discharges of clinical importance are followed by a slow
wave or series of slow deflections.

3. Benign EEG Variants(BEVs)
• The BEVs are waveforms that have an epileptiform appearance but
are not epileptogenic.
• The BEVs may be sharp contoured, or may occur as rhythmic bursts or
trains.
• The BEVs occur during drowsiness and light sleep.
• Accurate identification of the BEVs requires considerable training
and experience.

4. Alpha variants
• Slow alpha variant-occipital regions at a frequency one half that of
the ongoing PDR.
• It attenuates with eye opening.
• Fast alpha variant-occipital areas and has a frequency twice that of
the PDR.

6. Mu rhythm
• Central derivations (C3/C4) over the motor strip
• It may be unilateral or bilateral
• More evident during drowsiness and when the eyes are open.
• Considered to be related to beta activity.
• Mu attenuates with movement of the opposite upper limb.
• It is often prominent over the site of a craniotomy.

8. Lambda waves
• Occipital regions.
• They are sharply contoured, usually symmetric.
• Probably represent visual evoked potentials.

10. Rhythmic mid-temporal theta discharges (RMTD)
• Rhythmic sharply contoured theta waves at 5–6 Hz
• Midtemporal regions.
• The bursts are brief, usually 1 sec or so in duration
• May be unilateral or independent in both midtemporal regions.
• Appears during drowsiness.

12. Wicket spikes
• Wicket spikes are sharply contoured rhythmic frequencies varying
from 7–11 hz
• Maximal in the midtemporal derivations.
• Appearance of a sharp wave or a spike.
• Unlike epileptiform sharp waves or spikes, there is no aftergoing slow
wave.
• This finding occurs during drowsiness.

14. Subclinical rhythmic electroencephalographic discharges of adults
(SREDA)
• Older population (over 50 years of age)
• Seen in wake and sleep.
• Temporoparietal junction but can be seen at the vertex as well

15. • Symmetric or asymmetric bilateral bursts of rhythmic sharply
contoured theta activity
• Sudden appearance of repetitive sharp or slow waveforms that
become shorter in interval followed by a sustained burst that mimics
the evolution of an electrographic seizure.
• Usually lasts 40–80 seconds.

17. • Small sharp spikes (SSS)
• low-amplitude, rapid spikes.
• They appear in both hemispheres as synchronous or asynchronous
• Most often in the temporal derivations
• Evident during drowsiness and light sleep.
• Also known as benign epileptiform transients of sleep (bets).

19. Phantom spike-wave discharges
• Usually synchronous discharges at a frequency of 5–6 Hz appearing
symmetrically.
• Can have either an anterior or a posterior predominance.
• The spike itself is usually less prominent than the following slow
wave.
• Spikes appear individually or in brief rhythmic runs.

21. 14 and 6 (14/6) positive spikes
• Positive in polarity.
• They are usually maximal in the posterior quadrants and appear in
isolation or in groups.
• They may be unilateral or bilateral.
• The two frequencies are often admixed, but one may predominate.
• Appears during drowsiness.

23. • Alpha variant- occipital region
• Lambda waves- occipital region
• Mu rhythm- central derivations
• Wicket spikes- mid temporal
• Sharp spike waves- temporal junction
• SREDA- temporo parietal junction
• Phantom spikes- can have either anterior or posterior predominace

24. No-1

25. Mu -rhythm
• Alpha variant
• 7-11 HZ
• Arciform shaped / sharply contoured
• Maximum seen on C3- C4
• Drowsy state

27. Wicket Spikes
• Morphology : Monophasic Arciform
• Topography : Temporal,frontal leads
• Amplitude : 60-200 µV
• Frequency : 6-11 Hz
• Symmetry & Synchrony :Bilaterally Independently
• State of the Patient : Drowsiness & Light Sleep
• Background Activity : Not distorted ,no slow waves
• Could be mistaken for abnormal temporal epileptiform discharges

29. • Lamda waves

31. 6 Hz spikes and waves (Phantom spikes)

33. Small Sharp Spikes
Topography : Temporal , frontal leads
• Amplitude : 50 µV
• Frequency : Random
• Duration : <50 msec
• Symmetry & Synchrony : Asymmetric & Asynchronous
• State : Drowsiness & Light Sleep
• Background Activity : Not distorted

35. • Rhythmic mid-temporal theta discharges (RMTD)