1. For Neurology Residents
EEG
For Neurology Residents
2009

2. Not exactly EEG, but… …things you need to know. Epilepsy and driving.
Epilepsy and pregnancy

3. I. What is an EEG and how is it recorded ?
OUTLINE
I. What is an EEG and how is it recorded ?
II. How do you read an EEG ?
III. The use of EEG
IV. Slideshow/Quiz

4. WHAT IS AN EEG AND HOW IS IT RECORDED?
PART I
WHAT IS AN EEG AND HOW IS IT RECORDED?

5. Recording procedure 20-30 minutes, relaxed patient Eyes opened/closed
Photic stimulation, Hyperventilation
+/- sleep +/- pain, noise

7. PART II
HOW DO YOU READ AN EEG ?

8. Why do you need to know this?
Exams
Emergencies
To understand the reports

9. An organized approach Orient yourself.
Is there normal brain activity present or is it altered ?
Is there abnormal activity present ?
What is the state ?
Is it age – appropriate ?
Are there any artifacts present ?

10. 1. ORIENT YOURSELF Montage (bipolar or referential) F7, F8 Time scale
Sensitivity (amplitude, positive/negative)
Other channels (EKG, EOG)

11. 2. Is there normal brain activity or is it altered?
Is the stuff that is supposed to be there actually there ?
Is there evidence of a structural lesion or a toxic/metabolic process that has altered the normal EEG background activity?

12. Normal brain activity Waves: Delta 1-3 Hz
Theta Hz
Alpha Hz
Beta > 12 Hz
Posterior dominant alpha rhythm with eye closure.
Alpha rhythm ≠ alpha frequency
Low amplitude, frontal Beta activity.

13. The typical EEG

14. Normal deviations from normal (!)
Drowsiness
Sleep
Age (young and old!)
Activation procedures
(a) Hyperventilation
(b) Photic stimulation

15. Background abnormalities
Slowing (theta or delta)
Focal or diffuse
Bilaterally synchronous or not
Rhythmic vs. irregular/polymorphic
High vs. low amplitude
Intermittent vs. continuous
Can be more subtle
Attenuation of amplitude
Asymmetry of alpha
Etc…

16. Focal slowing

17. Generalized slowing Ebersole & Pedley

18. “Disturbance of the background activity”
Summary
Focal slowing
= rule out structural lesion
Generalized rhythmic slowing
= consider deep structural lesion or destructive process
Polymorphic generalized slowing
= very nonspecific
“Disturbance of the background activity”

19. 3. Abnormal activity
Is there any stuff there that should not be there at all ?
Not simply alteration of the background
Usually, we are asking if there is epileptic activity (interictal or ictal).

20. Focal Inter-ictal activity
Spikes and sharp waves !
Phase reversal
Recurrent and consistent
With a field
Followed by slow wave
Asymmetrical
Not explained by artifact

21. Focal epileptic activity

22. Focal epileptic activity

23. Terminology “Potentially epileptic abnormality”
“Epileptiform abnormality”
Spike, patting artifact, spike

24. Phase Reversal

25. Non-epileptic phase reversal (normal background activity)

26. Generalized Inter-ictal Activity
Generalized spike and wave

27. Ictal Activity (Seizures)
Electrographic lasts > 10 sec
Seizures not defined by single pattern; spikes, spike and wave, slowing, attenuation etc…
Rhythmic activity that changes with time

28. Partial complex seizure with secondary generalization

29. Neonatal seizure

30. Neonatal seizure cont…

31. 3 Hz spike and wave (from Ebersole and Pedley)

32. Summary Interictal epileptic activity = spikes and sharp waves
= evolving rhythmic activity

33. 4. State 4 Sleep stages, plus REM 1. Lose α, slow EOM, v-waves
2. Spindles, K-complex, v-waves
3. Delta < 50%
4. Delta > 50%
REM: -looks normal (i.e. awake), need EOG, EMG etc…
Sleep onset
Most consider stage 1 sleep = drowsiness
But…some define sleep onset as appearance of v-waves, others as sleep spindles.

34. Don’t Forget… 5. Age Prior to birth, continuous evolution of EEG
Posterior-dominant rhythm by 6-12 months; alpha frequency by 4-8 years
6. Artifacts
EKG or pulse
Eye movement
Electrode
Muscle/movement
Electrical
Weird and wonderful

35. Electrode artifact

36. Eye Movements

37. EKG Artifact

38. Head movement artifact during a pseudoseizure

39. So how do you read an EEG? “Plan and scan” Organized Approach Scanning
Orient
Normal
Abnormal
Age and State
Artifacts
Scanning
Vertical
Horizontal

40. Scanning

41. Focal slowing

42. If all else fails…
Describe what you see
From Fisch and Spehlmann