Cranial Nerve IX and X Weakness: An Unusual Initial Presentation of Myasthenia Gravis

Abstract

BACKGROUND Myasthenia gravis (MG) is an autoimmune disease characterized by antibodies binding skeletal muscle acetylcholine receptors (AChR). Rarely does the disease manifest with orolaryngeal symptoms before ocular ones. We present a case of MG that on initial presentation had symptoms of cranial nerves (CN) IX and X weakness, including dysphagia and dysphonia. CASE REPORT A 51-year-old woman with panic attacks presented to the Emergency Department (ED) with complaints of her throat closing, swallowing difficulty, and hoarse voice. Multiple ED visits revealed no etiology. However, she developed stridor, which prompted further evaluation. Laryngoscopy and imaging studies revealed no gross abnormalities; therefore, her symptoms of dysphonia and difficulty breathing were attributed to anxiety. Her hospital course was complicated by a cardiac arrest requiring intubation. ECHO, CTA chest, and MRI brain were unremarkable. Her cardiac arrest was hypothesized as being secondary to laryngeal spasm. During her ICU course, she failed extubation multiple times due to acute respiratory failure. An autoimmune etiology was suspected, prompting a paraneoplastic screen, which revealed elevated levels of AChR antibodies at 124 mmol/L. MG was diagnosed and treatment with plasmapheresis and steroids was initiated. However, complications of thrombocytopenia, anemia, and ARDS ensued, so MG treatment was discontinued. The patient was eventually transferred to a LTACH. Thereafter, at outpatient followup, her MG was treated with mycophenolate and prednisone, which led to significant symptom improvement. CONCLUSIONS MG commonly presents in the third decade with clinical features of ptosis, diplopia, and facial weakness. However, initial and isolated symptoms of dysphagia and dysphonia are rare, leading to missed diagnoses. Our case of a middle-aged woman posed a diagnostic challenge because of her uncommon presentation and comorbidities of panic attacks and obesity. This case highlights the crucial need for a high index of clinical suspicion for MG in any patient presenting with symptoms of CN IX and X weakness.