1. Benign EEG Variants And Patterns of Unknown Significance
Yvan Tran, MD
Saint Mary’s Epilepsy Program
4/27/13

2. No Disclosures

3. Learning Objectives
Understanding the importance of identifying benign variants
Understanding the broad categories of benign variants
Age predisposition for benign variants

4. Significance of Benign Variants
Understanding what is normal is just as important as picking up abnormal discharges.
Overinterpreting can lead to improper diagnosis with longer term consequences for patients.
Important to look at the discharges in the context of the background activity.
These variants can be seen in normal individuals or in patients with various complaints but has not been proven directly to indicate an increased epileptogenic risk.

5. Benign Variants Benign Patterns can be divided into two groups:
Rhythmic Patterns
Patterns with Epileptiform Morphology

6. Benign Variants With Rhythmic Patterns
Rhythmic Theta Burst of Drowsiness (RMTD) or Psychomotor Variant
Alpha Variant
Midline Theta Rhythm
Frontal Arousal Rhythm

7. Rhythmic Theta Burst of Drowsiness
Also known as RMTD or psychomotor variant
Seen in drowsiness
Bursts of rhythmic theta waves of 5-7 Hertz
Waves are notched or flat topped due to superimposition of faster frequencies on the background
Maximal in the midtemporal leads but can spread parasagittally
Can be seen bilaterally or shift independently from side to side.

8. Rhythmic Theta Burst of Drowsiness
Confused for epileptiform discharges due to the gradual increase and decrease of amplitude seen with the train of discharges.
Waves are usually monomorphic
Seen in 0.5%-2% of patients

9. Rhythmic Theta Burst of Drowsiness
Ernst Niedermeyer, Fernando H. Lopes da Silva. Electroencephalography: basic principles, clinical applications, and related fields. 2005

10. Alpha Variant
Same distribution as the normal background rhythmposterior quadrants
Is a harmonic of the normal alpha rhythm
Slow alpha variant
A subharmonic with frequencies between 4-5 Hz
Often notched
Fast alpha variant
A supraharmonic with frequencies between Hz
Pattern is reactive
Seen in the relaxed awake state
Often alternates with the normal alpha pattern

11. Slow Alpha Variant
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

12. Midline Theta Rhythm
Focal rhythm over the central leads, usually maximal at Cz
Arciform appearance between 5-7 Hz
Pattern waxes and wanes
Present during wakefulness and drowsiness
Reactive pattern including with limb movements

13. Midline Theta Rhythm
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

14. Frontal Arousal Rhythm
Seen in children upon arousal
Bursts last up to 20 secs
Frequency of 7-20 Hz
Often waveforms are notched due to varying harmonic activity
Resolves once full wakefulness is achieved

15. Frontal Arousal Rhythm
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

16. Benign Variants With Epileptiform Morphology
Fourteen and Six Hertz Positive Bursts
Small Sharp Spikes (SSS)
Six Hertz Spike and Wave Burst (Phantom Spike and Wave)
Wicket Spikes
Breech Rhythm

17. 14-and-6 Hz Positive Bursts
Aka 14-and-6 Hz Spikes
Seen during drowsiness and light sleep
Usually seen in 3-20 y/o, peak at y/o
In trains of arch-shaped waves of alternating with positive spiky waves with rounded negative waves
Duration is sec
Maximal over the posterior temporal regions
Best seen on referential montage with shifting lateralization

18. 14-and-6 Hz Positive Bursts
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

19. Small Sharp Spikes (SSS)
Aka Benign epileptiform transients of sleep (BETS) and benign sporadic sleep spikes.
Seen during drowsiness and light sleep
Seen in adults
Low voltage averaging <50µV with a duration of <50ms
Can be monophasic or diphasic
Can be confused for epileptiform activity due to the occasional aftergoing slow wave
Seen best in temporal and ear lead with derivation of long interelectrode distance.
They do not occur in trains and decrease with deeper stages of sleep
Seen in 20-25% of patients
Can be seen bilaterally or independently

20. Small Sharp Spikes
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

21. Six Hertz Spike and Wave Burst
Aka Phantom Spike and Wave
Duration is usually 1-2 secs
Seen in adolescents and adults during relaxed wakefulness and drowsiness
Seen in 2.5% of patients
Pattern is usually diffuse and synchronous bilaterally
Two variants:
FOLD (female occipital predominant low amplitude and drowsiness)--more benign variant
WHAM (wake high amplitude anterior predominant in male)—possible associated with seizures
Waveforms tend to disappear in sleep

22. Six Hertz Spike and Wave Burst
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

23. Wicket Spikes
Clusters or trains of monophasic arciform waveforms similar to the Greek mu (µ), however can occur single waveform
Not associated with an aftergoing slow wave or disruption of the background
Seen during drowsiness and light sleep
Seen in the temporal regions bilaterally or independently with shifting lateralization
Frequency is 6-11 Hz at µV
Seen in adults >30 y/o at incidence of 0.9%

24. Wicket Spikes
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

25. Breech Rhythm
High voltage activity of 6-11 Hz seen in regions overlying a skull defect.
Seen best over the central and temporal regions
Voltage is affected by the presence or absence of bone, bone reabsorption and region of skull defect.
Beta activity is enhanced

26. Breech Rhythm
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

27. Patterns of Unknown Significance
Subclinical Rhythmic Electrographical Discharge of Adults (SREDA)

28. Subclinical Rhythmic Electrographical Discharge of Adults
Fairly uncommon
Seen in individuals usually greater than 50
Seen in resting and drowsy states
Increased or precipitated by hyperventilation
Rhythmic theta and delta waves that are sharply contoured and typically evolve into a rhythmic frequency of 5-7 Hz.
Usually seen in a generalized pattern with predominance over the parietal and posterior temporal regions; At times can be lateralized.
Range is 20 secs to several minutes, Mean is secs
Abrupt onset
Waves are monophasic

29. SREDA
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

30. Wicket Spikes
Santoshkumar et al. Clin Neurophysiol 2009; 120:856-61

31. SREDA
Ebersole. J., Pedley T. Current Practice of Clinical Electroencephalography

32. Six Hertz Spike and Wave Burst
Santoshkumar et al. Clin Neurophysiol 2009; 120:856-61

33. Wicket Spike
Krauss GL, Abdallah A, Lesser R, Thompson RE, Niedermeyer E. Clinical and EEG features of patients with EEG wicket rhythms misdiagnosed with epilepsy. Neurology 2005;64:1879-1

34. 14-and-6 Hz Positive Bursts
Santoshkumar et al. Clin Neurophysiol 2009; 120:856-61

35. Rhythmic Theta Burst of Drowsiness

36. 14-and-6 Hz Positive Bursts
Ernst Niedermeyer, Fernando H. Lopes da Silva. Electroencephalography: basic principles, clinical applications, and related fields. 2005

37. RMTD
Santoshkumar et al. Clin Neurophysiol 2009; 120:856-61

38. Small Sharp Spikes
Richard, L. INTRODUCTION TO SLEEP ELECTROENCEPHALOGRAPHY

39. Wicket Spike
Richard, L. INTRODUCTION TO SLEEP ELECTROENCEPHALOGRAPHY

40. Six Hertz Spike and Wave Burst
Ernst Niedermeyer, Fernando H. Lopes da Silva. Electroencephalography: basic principles, clinical applications, and related fields. 2005