Physical Therapy Assistant Practice Exam

What is the MOST likely diagnosis for a patient with significant weakness of the face and proximal limbs associated with neuromuscular junction issues?

1. Multiple sclerosis

2. Myasthenia gravis

3. Amyotrophic lateral sclerosis

4. Poliomyelitis

The correct answer is: Myasthenia gravis

Myasthenia gravis is the most likely diagnosis for a patient presenting with significant weakness localized to the face and proximal limbs, particularly in the context of neuromuscular junction issues. This autoimmune disorder is characterized by weakness that typically worsens with exertion and improves with rest, affecting voluntary muscle control. The weakness often begins with ocular muscles, leading to ptosis or diplopia, and can progress to affect facial and proximal limb muscles, causing difficulties in tasks such as chewing, swallowing, and arm movements. The underlying mechanism involves antibodies that target the acetylcholine receptors at the neuromuscular junction, impairing the transmission of nerve impulses to muscles, which manifests as the muscle weakness seen in patients with this condition. Other options like multiple sclerosis, amyotrophic lateral sclerosis, and poliomyelitis involve different pathophysiological mechanisms that do not primarily affect the neuromuscular junction in the same manner or do not present with the specific pattern of weakness described. For instance, multiple sclerosis is a demyelinating disease of the central nervous system and presents with a variety of neurological symptoms. Amyotrophic lateral sclerosis affects motor neurons rather than the neuromuscular junction, leading to different patterns of weakness and muscle atrophy