EMG EMG Clinical Applications & Pathology

Question 1

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

Accepted Answer

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

Answer

Purely sensory nerve conduction slowing with normal needle EMG

Answer

Isolated proximal muscle fibrillations limited to one limb

Answer

Normal EMG with prolonged F-wave latencies only

Question 2

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

Accepted Answer

Prolonged median sensory peak latency across the wrist

Answer

Absent median motor CMAP

Answer

Prolonged ulnar distal motor latency

Answer

Reduced sural sensory amplitude

Question 3

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

Accepted Answer

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

Answer

Reduced CMAP amplitudes with normal conduction velocities

Answer

Absent sensory responses with preserved motor conduction

Answer

Normal motor studies with reduced sensory amplitudes only

Question 4

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

Accepted Answer

Inflammatory myopathy such as polymyositis

Answer

Chronic neurogenic disorder such as spinal muscular atrophy

Answer

Acute denervation injury

Answer

Neuromuscular junction disorder such as myasthenia gravis

Question 5

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

Accepted Answer

Length-dependent polyneuropathy with distal sensorimotor involvement

Answer

Bilateral L5 radiculopathy

Answer

Bilateral common peroneal mononeuropathy

Answer

Lumbosacral plexopathy

Question 6

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

Accepted Answer

Abnormal spontaneous activity in the cervical paraspinal muscles

Answer

Prolonged median motor distal latency

Answer

Reduced median sensory nerve action potential amplitude

Answer

Absent H-reflex