EMG Clinical Applications & Pathology Flashcards

Which EMG finding is most characteristic of amyotrophic lateral sclerosis (ALS)?

Answer: Widespread active denervation with fasciculation potentials in multiple limbs and the tongue

ALS produces widespread active denervation (fibrillations, fasciculations) across multiple body regions including bulbar muscles, reflecting both upper and lower motor neuron involvement.

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

Answer: Prolonged median sensory peak latency across the wrist

Prolonged median sensory peak latency across the wrist segment is the earliest and most sensitive electrodiagnostic finding in carpal tunnel syndrome.

What pattern of abnormality on nerve conduction studies is most consistent with Guillain-Barré syndrome (AIDP subtype)?

Answer: Prolonged distal latencies, slowed conduction velocities, conduction block, and temporal dispersion

AIDP (the most common GBS subtype in the US) is a demyelinating neuropathy characterized by prolonged distal latencies, slow conduction velocities, conduction block, and temporal dispersion.

Which myopathy typically shows short-duration, low-amplitude, polyphasic motor unit potentials (MUPs) with early recruitment on needle EMG?

Answer: Inflammatory myopathy such as polymyositis

Inflammatory myopathies such as polymyositis produce myopathic MUPs (short duration, low amplitude, polyphasic) with early recruitment due to loss of individual muscle fibers.

A patient with bilateral foot drop, absent ankle reflexes, and stocking-glove sensory loss most likely has which electrodiagnostic pattern?

Answer: Length-dependent polyneuropathy with distal sensorimotor involvement

Stocking-glove distribution with absent ankle reflexes is the hallmark of length-dependent polyneuropathy, where the longest nerve fibers are affected first.

Which EMG finding best differentiates a C7 radiculopathy from a median nerve lesion at the elbow?

Answer: Abnormal spontaneous activity in the cervical paraspinal muscles

Abnormal spontaneous activity in cervical paraspinal muscles (which are innervated proximal to the plexus) localizes the lesion to the root level, distinguishing radiculopathy from a peripheral nerve lesion.