ABEM Neuromuscular Disorders & Diagnostic Criteria 3

Question 1

On needle EMG, which MUAP characteristic most strongly suggests a myopathic process?

Accepted Answer

Early recruitment of short-duration, low-amplitude, polyphasic MUAPs

Answer

Myopathic MUAPs are short in duration and low in amplitude due to loss of muscle fibers per motor unit, and early recruitment occurs because more units fire to compensate for reduced force per unit.

Question 2

In critical illness polyneuropathy (CIP), which electrodiagnostic pattern is expected?

Accepted Answer

Axonal sensorimotor neuropathy with low CMAP and SNAP amplitudes and active denervation

Answer

CIP is an axonal sensorimotor polyneuropathy occurring in critically ill patients, characterized by reduced CMAP and SNAP amplitudes with fibrillations on needle EMG, without significant conduction velocity slowing.

Question 3

A patient with diabetic lumbosacral radiculoplexus neuropathy (diabetic amyotrophy) would most likely show which finding on needle EMG of the affected limb?

Accepted Answer

Active denervation in multiple lumbar myotomes including paraspinal muscles

Answer

Diabetic amyotrophy (Bruns-Garland syndrome) affects lumbosacral plexus and roots, causing active denervation across multiple myotomes including paraspinal muscles, confirming the proximal and radicular involvement.

Question 4

Which electrodiagnostic feature differentiates multifocal motor neuropathy (MMN) from ALS?

Accepted Answer

MMN shows conduction block in motor nerves without sensory involvement; ALS does not

Answer

MMN is defined by persistent, multifocal motor conduction block with preserved sensory conduction, while ALS shows pure lower motor neuron and upper motor neuron signs without conduction block.

Question 5

In hereditary neuropathy with liability to pressure palsies (HNPP), NCS most commonly reveals:

Accepted Answer

Focal conduction slowing or conduction block at typical entrapment sites with mild diffuse slowing

Answer

HNPP (PMP22 deletion) causes disproportionate focal slowing or block at entrapment sites (carpal tunnel, fibular head) superimposed on mild diffuse sensorimotor demyelinating changes.

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

ABEM Neuromuscular Disorders & Diagnostic Criteria 3