Benign variants of eeg
- 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)