Benign variants of eeg

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. I t attenuates with eye opening. Fast alpha variant-occipital areas and has a frequency twice that of the PDR.

5. 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.

6. Lambda waves O ccipital regions. They are sharply contoured, usually symmetric . P robably represent visual evoked potentials.

7. Rhythmic mid-temporal theta discharges (RMTD) R hythmic sharply contoured theta waves at 5–6 Hz Midtemporal regions. The bursts are brief, usually 1 sec or so in duration M ay be unilateral or independent in both midtemporal regions. A ppears during drowsiness.

8. 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.

9. 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

10. 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. U sually lasts 40–80 seconds.

11. 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).

12. Phantom spike-wave discharges U sually synchronous discharges at a frequency of 5–6 Hz appearing symmetrically. C an 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.

13. 14 and 6 (14/6) positive spikes P ositive 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.

14. 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

15. No-1

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

17. 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

18. Lamda waves

19. 6 Hz spikes and waves (Phantom spikes)

20. 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

21. Rhythmic mid-temporal theta discharges (RMTD)