(Kiosk 3) An Atypical Presentation of Myasthenia Gravis: A Case of Focal Wrist Drop Without the Presence of Oculobulbar Symptoms

Case Diagnosis: Myasthenia Gravis

Case Description: 38-year-old male presented with a 3-week history of progressive extensor weakness at the right wrist and fingers. He endorsed associated numbness and tingling in the fingers, difficulty opening containers, dropping items, and a heavy sensation in his upper lip with difficulty moving it. He had no other weakness, sensory complaints, diplopia, dysphagia or other symptoms of cranial nerve or sphincter dysfunction. Physical exam demonstrated wrist and finger weakness with otherwise normal strength and sensation and a normal cranial nerve exam.

Discussion: Myasthenia Gravis is the most common neuromuscular junction disorder. Typical presentation includes symmetrical proximal muscle weakness, muscle fatigue with repetition, and oculobulbar muscle weakness resulting in diplopia, blurred vision, and dysarthria. Distal extremity involvement has rarely been documented in late stages of Myasthenia Gravis, and it is even more uncommon as an initial presenting sign of Myasthenia Gravis.

Setting: Outpatient Physical Medicine and Rehab (PM&R) Clinic

Assessment/Results: Cervical X-Ray, cervical MRI, and CT-head were unrevealing. Nerve conduction studies showed median neuropathy, needle electromyography (EMG) was normal, and repetitive nerve conduction studies were normal except of the radial nerve, with a characteristic decrement of Myasthenia Gravis. Acetylcholine Receptor Antibody testing was positive, and GM-1 antibodies were normal. CT-chest showed non-specific increased thymic tissue attenuation. The patient deferred treatment with pyridostigmine and corticosteroids.

Conclusion: This case uniquely demonstrates unilateral wrist drop as a known but rare initial presentation of Myasthenia Gravis. In the absence of other more common explanations, clinicians should be considerate of such atypical clinical findings to assure prompt workup, diagnosis, and treatment of Myasthenia Gravis.