ABEM Nerve Conduction Studies & Electromyography 2

Question 1

Which parameter is most affected by limb temperature cooling during nerve conduction studies?

Accepted Answer

Conduction velocity

Answer

Cooling slows sodium channel kinetics, prolonging action potential duration and reducing conduction velocity by approximately 2 m/s per degree Celsius.

Question 2

A patient presents with median nerve mononeuropathy. On NCS, the distal motor latency is prolonged but conduction velocity across the forearm segment is normal. This pattern is most consistent with:

Accepted Answer

Focal demyelination at the carpal tunnel

Answer

Focal demyelination at the carpal tunnel produces prolonged distal latency while leaving proximal conduction velocity intact.

Question 3

On EMG, which finding most specifically indicates active denervation rather than chronic reinnervation?

Accepted Answer

Fibrillation potentials and positive sharp waves

Answer

Fibrillation potentials and positive sharp waves reflect spontaneous activity of denervated muscle fibers and indicate active denervation.

Question 4

In ulnar neuropathy at the elbow, inching technique is used to:

Accepted Answer

Localize the exact site of focal conduction slowing

Answer

Inching stimulates at 1–2 cm intervals across the elbow to pinpoint the site of maximal conduction slowing or conduction block.

Question 5

Which EMG finding is characteristic of myotonic dystrophy type 1?

Accepted Answer

Myotonic discharges waxing and waning in amplitude and frequency

Answer

Myotonic discharges classically wax and wane in both amplitude and frequency, producing the 'dive bomber' sound on EMG.

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

ABEM Nerve Conduction Studies & Electromyography 2