EMG Nerve Conduction Studies 3

Question 1

In a preganglionic nerve root avulsion (proximal to the dorsal root ganglion), what is the expected sensory NCS finding in the affected territory?

Accepted Answer

Normal or preserved SNAP despite clinical sensory loss

Answer

Because the dorsal root ganglion (DRG) is spared in a preganglionic avulsion, the peripheral sensory axon does not undergo Wallerian degeneration, preserving the SNAP even though the patient has complete clinical sensory loss.

Question 2

For reliable across-elbow ulnar nerve conduction velocity measurement, the minimum recommended distance between below-elbow and above-elbow stimulation points is:

Accepted Answer

10 cm

Answer

A minimum across-elbow distance of 10 cm is recommended to minimize the proportional impact of measurement error on the calculated conduction velocity; shorter segments risk falsely calculated slowing.

Question 3

Recording the CMAP from the abductor digiti minimi (ADM) is used to evaluate which nerve?

Accepted Answer

Ulnar nerve

Answer

The abductor digiti minimi is innervated by the deep branch of the ulnar nerve; recording CMAP from ADM while stimulating the ulnar nerve at the wrist and elbow is a standard ulnar motor NCS technique.

Question 4

In peroneal nerve palsy at the fibular head, which NCS finding best distinguishes focal demyelination from axonal loss at that site?

Accepted Answer

Conduction block or focal velocity slowing across the fibular head segment

Answer

Focal demyelination at the fibular head produces conduction block or marked velocity slowing across that segment while the distal CMAP amplitude remains relatively preserved; pure axonal loss reduces amplitude at all stimulation sites.

Question 5

The minimum number of F-wave trials recommended per nerve to reliably determine minimum F-wave latency is:

Accepted Answer

10

Answer

AANEM guidelines recommend a minimum of 10 F-wave trials per nerve to reliably capture the minimum latency F-wave and assess chronodispersion without excessive patient discomfort.

(EMG) Electromyography Certification Practice Test

(EMG) Electromyography Certification Practice Test

EMG Nerve Conduction Studies 3