Neurophysiology

Question 1

What is EEG useful for?

Answer 1

• Seizures/epilepsy - risk of recurrence and classification (NOT USED TO DIAGNOSE OR EXCLUDE)
• Recording events - long-term monitoring
• Coma/altered consciousness - wide differential diagnosis, to identify treatable causes (i.e. non-convulsive status epilepticus, encephalopathy)
• Dementia, cognitive decline - only useful in certain scenarios

NB - Useful to record along with video (videotelemetry)

Question 2

Leads on an EEG

Answer 2

• F - frontal
• T - temporal
• O - occipital
• C - central
• P - parietal

Question 3

Epileptiform activity on an EEG

Answer 3

• Spikes and sharp waves - activity which stands out from the background
• Generalised or focal - helps classify once diagnosis made (all leads = generalised, some leads - focal)

Question 4

Electromygraphy (EMG)

Answer 4

• Demyelinating (i.e. GBS) - action potentials delayed
• Axonal (i.e. diabetes, alcohol) - action potentials smaller

NB - Can also use needle EMG to see voluntary activation and recruitment of muscles over fasciculations and fibrillations.

EMG used for muscle disorders, NMJ disorders, entrapments and peripheral neuropathies.

Question 5

Evoked potentials

Answer 5

• Stimulate peripheral receptor or a peripheral nerve (eyes, ears, median or tibial nerves)
• Record cortical response
• Used to identify silent or previous demyelinating lesions