EEG

Question 1

What are criteria for interictal epileptiform discharges?

Answer 1

<200ms duration
Clearly distinguished from background
Abrupt change
Physiologic field

Question 2

What is the change in dynamic in focal epilepsy ictal EEG?

Answer 2

Change in amplitude
Change in frequency
Propagation
EEG onset and offset

Question 3

What is the sensitivity of 1st EEG for epilepsy?

Answer 3

40%
Repeat EEG doubles this

Question 4

What is the specificity for 1st EEG in epilepsy?

Answer 4

96%+

Question 5

What signs of epilepsy have high PPV?

Answer 5

Contralateral dystonic posturing 94%
Unilateral automatisms 100%
Postictal dysphasia 100% (non dominant)
Contralateral clonic movements 92%
Contralateral forced head version 94%

Question 6

Is EEG used for diagnosis?

Answer 6

No. Only supportive.
EEG does not prove/disprove existence of epilepsy

Question 7

What do alpha waves concomitant with unresponsiveness indicate?

Answer 7

Dissociation

Question 8

What might EEG reveal about encephalopathy?

Answer 8

Severity by degree of slowing of waves
Delta brush indicates anti NMDAR

Question 9

What else might cause slowing of waves?

Answer 9

Drowsiness/drugs

Question 10

What is the frequency of alpha waves?

Answer 10

8-12 hz

Question 11

What do waves slow to before generalised seizure?

Answer 11

4-6 Hz (theta)

Question 12

How do benzodiazepines affect EEG activity?

Answer 12

Increase beta (fast) activity