1. Common Mistakes in Interpretation of Outpatient EEG
June 2017
Dr. Mark Sadler Professor of Medicine (Neurology) Dalhousie University Halifax, Nova Scotia

2. Objective: To Review Some Common Errors in Adult Outpatient EEG Interpretation
Personal Observations
Reviewing EEG recordings/reports from outside laboratories
As a CSCN EEG Examiner
Literature Review: Scanty

4. An additional disclosure…
WTB School of EEG

5. Sequence… General Comments
Benign transients that mimic interictal epileptic abnormalities
Selected Comments on Generalized and Focal spikes
Benign rhythms that may mimic an ictal rhythm

6. General Comments: Avoiding Interpretation Errors
Read “blind” to clinical history: keeps you honest; keeps your attention
“Overcalling” vs “Undercalling”
Be conservative: abnormalities will eventually declare themselves
More recording time
Try to be helpful to referring physician… “put on your CLINICIAN’S hat” (Blume)

7. Transients vs. Rhythms Benign patterns that “look like spikes”
Benign patterns that “look like seizures”
Comments on interictal spikes (Focal; Generalized)

8. First: Review the Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”? 
Di- or Tri- phasic?
Polarity?
“Reasonable” field?
Aftercoming slow wave?
Disrupt the background?
Could it be artifact?
Could it be “benign”?
Consider the state (sleep?)
Official definition?

9. The Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”?
Di- or Tri- phasic? 
Polarity?
“Reasonable” field?
Aftercoming slow wave?
Disrupt the background?
Could it be artifact?
Could it be “benign”?
Consider the state (sleep?)
Official definition?

10. The Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”?
Di- or Tri- phasic?
Polarity? 
“Reasonable” field?
Aftercoming slow wave?
Disrupt the background?
Could it be artifact?
Could it be “benign”?
Consider the state (sleep?)
Official definition?

11. The Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”?
Di- or Tri- phasic?
Polarity?
“Reasonable” field? 
Aftercoming slow wave?
Disrupt the background?
Could it be artifact?
Could it be “benign”?
Consider the state (sleep?)
Official definition?

12. The Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”?
Di- or Tri- phasic?
Polarity?
“Reasonable” field?
Aftercoming slow wave?
Disrupt the background?
Could it be artifact?
Could it be “benign”?
Consider the state (sleep?)
Official definition?

13. The Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”? 
Di- or Tri- phasic?
Polarity?
“Reasonable” field?
Aftercoming slow wave?
Disrupt the background? 
Could it be artifact?
Could it be “benign”?
Consider the state (sleep?)
Official definition?

14. The Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”? 
Di- or Tri- phasic?
Polarity?
“Reasonable” field?
Aftercoming slow wave?
Disrupt the background?
Could it be artifact? 
Could it be “benign”?
Consider the state (sleep?)
Official definition?

15. The Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”? 
Di- or Tri- phasic?
Polarity?
“Reasonable” field?
Aftercoming slow wave?
Disrupt the background?
Could it be artifact?
Could it be “benign”? 
Consider the state (sleep?)
Official definition?

16. The Classic “Pathologic” Spike or Sharp Wave
Is it “sharp”? 
Di- or Tri- phasic?
Polarity?
“Reasonable” field?
Aftercoming slow wave?
Disrupt the background?
Could it be artifact?
Could it be “benign”?
Consider the state (sleep?) 
Official definition?

17. Benign “Sharply Contoured” Transients
Wicket spikes
Benign epileptiform transients of sleep (BETS) or small sharp spikes (SSS)
Six per second spike and wave
14 Hz positive waves
Normal physiology:
Vertex waves
POSTS
Lambda
Breach rhythm
Mu rhythm
Artifacts (ECG, muscle, etc)

18. Benign “Sharply Contoured” Transients
Wicket spikes
Benign epileptiform transients of sleep (BETS) or small sharp spikes (SSS)
Six per second spike and wave
14 Hz positive waves
Normal physiology:
Vertex waves
POSTS
Lambda
Breach rhythm
Mu rhythm
Artifacts (ECG, muscle, etc)

19. Reiher & Lebel: CJNS 1977

20. Wicket Spikes Sharply contoured Midtemporal Isolated or in trains
No aftercoming slow wave
No disruption of background – part of it
Most common error in misdiagnosis of epilepsy (Benbadis, 2008)

21. Wicket Spikes

22. Benign “Sharply Contoured” Transients
Wicket spikes
Benign epileptiform transients of sleep (BETS) or small sharp spikes (SSS)
Six per second spike and wave
14 Hz positive waves
Normal physiology:
Vertex waves
POSTS
Lambda
Breach rhythm
Mu rhythm
Artifacts (ECG, muscle, etc)

23. Benign Epileptiform Transients of Sleep (Small Sharp Spikes)
Common!
Drowsiness and light sleep
Usually < 50 microvolts (“small”) but can be “big”
Monophasic/diphasic; VERY sharp (“needle” like)
Aftercoming slow wave (sometimes)
Temporal location BUT large, gently sloping field (“difficult to localize”): *Use of coronal montage*
Often independent bilateral

24. BETS: A-P Bipolar

25. SSS: Coronal: Excellent montage for identification

26. SSS: CAR: Contamination of reference? Large field? Both?

27. BETS: LEFT Mastoid Reference
Note Large Right Hemisphere Field
Note contamination of reference

28. Benign “Sharply Contoured” Transients
Wicket spikes
Benign epileptiform transients of sleep (BETS) or small sharp spikes (SSS)
Six per second spike and wave
14 Hz positive waves
Normal physiology:
Vertex waves
POSTS
Lambda
Breach rhythm
Mu rhythm
Artifacts (ECG, muscle, etc)

29. Six-Hz Spike and Wave
Short bursts (less than 1 second); usually bilateral
Relatively small spike compared to aftercoming slow (“phantom spike waves” – Gibbs and Gibbs)
Drowsiness and relaxed wakefulness; not in deeper sleep
FOLD (Female, Occipital, Low voltage, Drowsy) (Hughes, 1980) = Not associated with Sx
WHAM (Wake, High voltage, Anterior, Male); higher association with Sx
What to say in clinical interpretation?

30. Six per Second Spike and Wave

31. Vertex Waves
Comment: VERY apiculate in childhood; much less so in elderly
Distinguish from CZ spikes

32. POSTS and Lambda Waves
Attention to the STATE of the patient, eyes open/closed, and POLARITY will solve this problem
Distinguish from occipital spikes

33. Lambda
Patient Reading

34. Transients vs. Rhythms Benign patterns that “look like spikes”
Some comments on interictal spikes
Generalized
Focal Temporal
Benign patterns that “look like seizures”

35. 27 year old with Hx of Absences & GTC Seizures

36. Same Patient: Fragments: Should not deter you from Dx of GGE

37. Electrical Field of Temporal Spikes
Gibbs FA, Gibbs EL. Atlas of Electroencephalography F7
Rahey S, Sadler RM, 1990

38. Field of Anterior Temporal Spikes and Electrodes
Silverman “Anterior temporal” (T1-2)
Mandibular notch (MN1-2)
“Mini-sphenoidal”
Sphenoidal
Semi-invasive
Foramen ovale
Invasive
Nasopharyngeal
Historical interest only

39. Expanded Positions

40. Extra Electrodes: Which is best?
Many studies; most unblinded and small numbers
Sadler and Goodwin (1989): SP, MN (surface or subdermal), AT all > NP, F7/8, A1/2
Bottom line: “SP, MN, AT are better than none”; add electrodes inferior to original standard positions

41. Montage for Anterior-Mesial Temporal Epilepsy
Combined coronal and AP bipolar
Use additional inferior electrodes (no excuses in digital era)
“Double length” sleep deprived recording

44. Transients vs. Rhythms Benign patterns that “look like spikes”
Some comments on interictal spikes
Generalized
Focal Temporal
Benign patterns that “look like seizures”

45. Benign Patterns May Look Like Seizures
Rhythmic Temporal Theta Bursts of Drowsiness
Slow alpha variant
Others…

46. Benign Patterns May Look Like Seizures
Rhythmic Temporal Theta Bursts of Drowsiness
Slow alpha variant

47. Rhythmic Temporal Theta Bursts of Drowsiness (RMTD; PMV)
08:42:0308:42:03

48. Rhythmic Temporal Theta Bursts of Drowsiness (RMTD; PMV)
08:42:03
08:42:19

49. Rhythmic Temporal Theta Bursts of Drowsiness (RMTD; PMV)
Burst or train of 4-6 Hz rhythmic waves; often “notched”.
Mainly temporal location
Unilateral, bilateral, or shifting from side-to-side
Drowsiness promotes its appearance
Does NOT evolve like a seizure!
Highly reactive (e.g. eye opening aborts)

50. Failure to Employ Activation Techniques for NES?
May obviate need for inpatient video-EEG
Have a protocol

51. Thank You! See You in 2018