EMG Nerve Conduction Studies 2

Question 1

Which pattern of NCS findings is most characteristic of a demyelinating polyneuropathy?

Accepted Answer

Prolonged latencies, slowed conduction velocities, and possible conduction block

Answer

Reduced amplitudes with normal conduction velocities

Answer

Absent F-waves with normal distal motor studies

Answer

Incremental CMAP response to repetitive nerve stimulation

Question 2

At low-frequency repetitive nerve stimulation (2–3 Hz), a greater than 10% decremental response in CMAP amplitude is characteristic of which condition?

Accepted Answer

Myasthenia Gravis

Answer

Lambert-Eaton Myasthenic Syndrome

Answer

Botulism (early stage)

Answer

Myotonic dystrophy

Question 3

High-frequency repetitive nerve stimulation (20–50 Hz) produces a significant incremental (facilitated) CMAP response exceeding 100% in which condition?

Accepted Answer

Lambert-Eaton Myasthenic Syndrome

Answer

Myasthenia Gravis

Answer

Congenital myasthenic syndrome

Answer

Botulism (chronic stage)

Question 4

When performing a median-to-ulnar sensory comparison study across the palm, a latency difference greater than how many milliseconds between the two nerves suggests carpal tunnel syndrome?

Accepted Answer

0.4 ms

Answer

0.2 ms

Answer

1.0 ms

Answer

2.0 ms

Question 5

In axonal polyneuropathy, what is the expected NCS pattern?

Accepted Answer

Normal or near-normal NCV with reduced CMAP and SNAP amplitudes

Answer

Slowed NCV with preserved CMAP and SNAP amplitudes

Answer

Conduction block at typical entrapment sites

Answer

Prolonged distal latencies with normal conduction velocities

Question 6

The reference (inactive) recording electrode in motor nerve conduction studies is optimally placed:

Accepted Answer

Over an electrically inactive area such as a tendon or bony prominence

Answer

Proximal to the active electrode along the nerve trunk

Answer

At the stimulation site cathode

Answer

At a point equidistant between the two stimulation sites

Question 7

The medial antebrachial cutaneous nerve, commonly studied in brachial plexus evaluations, arises from which structure?

Accepted Answer

Medial cord of the brachial plexus

Answer

Posterior cord of the brachial plexus

Answer

Lateral cord of the brachial plexus

Answer

C5-C6 nerve roots directly