ABEM Neuromuscular Disorders & Diagnostic Criteria

Question 1

Which of the following is a hallmark symptom of myasthenia gravis?

Accepted Answer

Fluctuating muscle weakness

Answer

Myasthenia gravis is an autoimmune disorder characterized by fluctuating muscle weakness that worsens with activity and improves with rest. This hallmark symptom is due to antibodies blocking or destroying acetylcholine receptors at the neuromuscular junction, impairing signal transmission between nerves and muscles. The variability in weakness throughout the day or with exertion is highly characteristic.

Question 2

What test is commonly used to diagnose Guillain-Barré Syndrome?

Accepted Answer

Nerve conduction studies

Answer

Guillain-Barré Syndrome (GBS) is an acute inflammatory demyelinating polyneuropathy affecting the peripheral nervous system. Nerve conduction studies (NCS) are critical for diagnosing GBS by revealing characteristic findings such as slowed conduction velocities, prolonged latencies, and conduction blocks. These findings indicate widespread demyelination of peripheral nerves, which is the pathological basis of GBS.

Question 3

What is a common diagnostic feature of amyotrophic lateral sclerosis (ALS)?

Accepted Answer

Combined upper and lower motor neuron signs

Answer

Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease that uniquely affects both upper motor neurons (in the brain and spinal cord) and lower motor neurons (in the brainstem and spinal cord). This combination leads to a distinct clinical presentation of both spasticity, hyperreflexia (upper motor neuron signs), and muscle weakness, atrophy, and fasciculations (lower motor neuron signs). This dual involvement is a key diagnostic feature.

Question 4

Which neuromuscular disorder typically shows a decremental response on repetitive nerve stimulation?

Accepted Answer

Myasthenia gravis

Answer

Myasthenia gravis is characterized by a decremental response on repetitive nerve stimulation, meaning the amplitude of the muscle action potential decreases with successive stimulations. This occurs because the limited number of available acetylcholine receptors at the neuromuscular junction become progressively saturated or desensitized. This impaired neuromuscular transmission leads to the observed decrement.

Question 5

What condition is primarily characterized by muscle inflammation and weakness?

Accepted Answer

Polymyositis

Answer

Polymyositis is an inflammatory myopathy primarily characterized by inflammation of the muscles, leading to progressive muscle weakness, particularly in the proximal muscles. This condition is distinct from neuropathies or other muscle disorders as its primary pathology involves direct inflammation within the muscle tissue itself. The inflammation causes muscle fiber damage and subsequent weakness.

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

ABEM Neuromuscular Disorders & Diagnostic Criteria