Disclosures: Lauren A. White, DO: No financial relationships or conflicts of interest

Case Description: Patient presented to the emergency department (ED) with three weeks of dysphagia and dysarthria; acutely worse over the last week. Computed tomography (CT) of the brain was negative for stroke, and he was discharged. He returned two days later with total inability to swallow, now unable to control his lower facial muscles. Magnetic resonance imaging (MRI) of brain and cervical spine showed asymmetric atrophy of the caudate nuclei suspicious for Huntington Disease; no infarct. Examination revealed facial diplegia, chorioform movements, intact deep tendon reflexes, and bilateral positive Babinski sign. Differential diagnoses included Guillain-Barré variants, motor neuron disease, and neuromuscular junction disorder. Cerebrospinal fluid was negative for albuminocytologic dissociation. Electromyography (EMG) showed diffuse denervation and neuropathic recruitment pattern in the genioglossus, bilateral upper extremities, and thoracic and lumbar paraspinal muscles. Facial and ulnar motor repetitive nerve stimulation (RNS) demonstrated >10% decrement at rest, and immediately and one minute post-exercise. Routine nerve conduction studies were unremarkable. Symptoms improved with intravenous immunoglobulin and pyridostigmine. Serum acetylcholine receptor antibodies were positive, confirming diagnosis of myasthenia gravis (MG). Further workup showed anterior mediastinal mass; biopsy positive for thymoma.

Setting: Tertiary care hospital

Patient: 66 year old male with history of diverticulitis, and family history of Huntington Disease in his mother.

Assessment/Results: He stabilized on pyridostigmine and was able to speak and swallow without issue. He later underwent thymoma resection just prior to submission; long term outcomes to follow.

Discussion: Fatigueable weakness is classic on RNS in MG. Motor unit action potentials are often small with short duration, in contrast to what we saw in our patient. Regardless, we suspect denervation was due to the severity of his disease rather than an additional neurologic process.

Conclusion: Cases of severe MG may show diffuse denervation and neuropathic recruitment on EMG. In these cases, serum antibody markers and full neurologic workup are especially important.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/rapid-onset-myasthenia-gravis-with-severe-denervation-and-neuropathic-recruitment/