EMG Nerve Conduction Studies

Question 1

Which nerve conduction parameter directly reflects the speed of the fastest-conducting motor nerve fibers between two stimulation points?

Accepted Answer

Nerve conduction velocity

Answer

Distal motor latency

Answer

CMAP amplitude

Answer

CMAP duration

Question 2

What does a reduced compound muscle action potential (CMAP) amplitude on motor nerve conduction studies primarily indicate?

Accepted Answer

Loss of functioning motor axons

Answer

Demyelination of motor fibers

Answer

Slowing of the fastest-conducting fibers

Answer

Increased temporal dispersion

Question 3

In adults, the H-reflex is most reliably and consistently obtained from which nerve-muscle pair?

Accepted Answer

Tibial nerve / soleus

Answer

Ulnar nerve / abductor digiti minimi

Answer

Median nerve / abductor pollicis brevis

Answer

Peroneal nerve / extensor digitorum brevis

Question 4

A prolonged F-wave latency with a normal distal motor latency and normal nerve conduction velocity most likely suggests:

Accepted Answer

Proximal conduction slowing or nerve root pathology

Answer

Focal entrapment at a distal site

Answer

Neuromuscular junction dysfunction

Answer

Pure sensory neuropathy

Question 5

In carpal tunnel syndrome, which NCS finding is typically the earliest and most sensitive indicator?

Accepted Answer

Prolonged median sensory peak latency across the wrist

Answer

Reduced CMAP amplitude at the wrist

Answer

Slowed median motor NCV in the forearm

Answer

Absent median F-wave

Question 6

The widely accepted AANEM criterion for definite conduction block is a reduction in CMAP amplitude or area with proximal versus distal stimulation of more than:

Accepted Answer

50%

Answer

20%

Answer

35%

Answer

75%

Question 7

Temporal dispersion in nerve conduction studies refers to:

Accepted Answer

Widening of CMAP duration with proximal versus distal stimulation

Answer

Increased CMAP amplitude with proximal stimulation

Answer

Decreased sensory latency at distal stimulation sites

Answer

Uniform slowing of conduction velocity across the entire nerve