Clinical Reasoning: Blurred vision and dancing feet

Abstract

A 58-year-old woman presented to a neuro-ophthalmologist with a 5-year history of progressively blurred vision, diplopia, and longstanding bilateral ptosis. She described occasional choking episodes after eating as well as fatigue and shortness of breath after minimal exertion. Her older sibling had received corrective eyelid surgery for ptosis and two nieces had ptosis and proximal myopathy and were being investigated in another center. Direct and consensual pupillary light reflexes were normal with no rapid alternating pupillary defect. Visual acuity was 20/20 on the right and 20/30 on the left. She had bilateral symmetric ptosis obscuring two-thirds of the pupil and restriction of eye movements below 60% of normal in all directions of gaze. Lower limb examination revealed symmetric proximal limb weakness (Medical Research Council grade 4+) with reduced reflexes and flexor plantars. Tandem gait was hesitant. ### Questions for consideration: 1. What are the possible diagnoses? 2. What initial investigations would you recommend? The initial differential diagnosis included Graves thyroid eye disease, a neuromuscular junction disorder (myasthenia gravis or botulism), oculopharyngeal muscular dystrophy, Miller Fisher variant of Guillain-Barre syndrome, and progressive muscular dystrophy. Free thyroxin and thyroid stimulating hormone levels were normal. Thyroid antibodies were negative. Acetylcholine receptor antibody assay was negative and repetitive nerve stimulation to exclude a neuromuscular junction disorder was normal. Electromyography of proximal upper limb muscles revealed an increased number of short duration motor units consistent with borderline myopathy. Nerve conduction velocities were …