Unilateral Ptosis and Bulbar Symptoms as the Initial Presentation of Late-Onset Acetylcholine Receptor Antibody-Positive Myasthenia Gravis Mimicking Acute Ischemic Stroke in an 82-Year-Old Man

Abstract

Myasthenia gravis is an autoimmune disorder of the neuromuscular junction. In older adults, it may present with bulbar and ocular symptoms that resemble acute stroke. Ocular myasthenia is typically asymmetric and often bilateral; persistent unilateral ptosis in this context can be misleading. An 82-year-old man with type 2 diabetes mellitus, chronic kidney disease, cataracts, and macular degeneration presented with a two-week history of fatigable dysphagia, slurred speech, and new-onset unilateral left ptosis. Symptoms were worse towards the end of the day. He denied diplopia and limb weakness. On examination, he was alert with marked left ptosis, mild left facial weakness, and normal limb strength and gait. A working diagnosis of ischemic stroke was made. Computed tomography of the head, magnetic resonance imaging of the brain with magnetic resonance angiography, and carotid Doppler ultrasound showed no acute vascular pathology. Speech and language therapy assessment demonstrated moderately dysarthric but functional speech and a safe swallow using compensatory strategies. ENT review was arranged as a safety assessment to exclude structural lesions or throat pathology in view of his recent swallowing difficulty, sensation of food sticking on the left side, and intermittent nasal speech later in the day; flexible nasal endoscopy was normal. Neurology review noted fluctuating bulbar symptoms with isolated unilateral ptosis, normal extraocular movements, and a normal limb examination, raising suspicion for myasthenia gravis. Pyridostigmine was started with rapid improvement in ptosis, speech, and swallowing. By the following day, both eyes were open, and he was seen reading, although transient recurrence of ptosis was observed during reassessment, consistent with fatiguability. Computed tomography of the chest excluded thymoma. During brief withdrawal of pyridostigmine for neurophysiology, unilateral ptosis and dysphagia recurred. Nerve conduction studies and limited single-fibre electromyography were non-diagnostic. Subsequent serology confirmed positive acetylcholine receptor antibodies (13.8) and negative anti-MuSK antibodies. He was treated with pyridostigmine and oral prednisolone with gastric and bone protection and close monitoring of glycaemic control. At follow-up, he remained asymptomatic, with full resolution of unilateral ptosis and bulbar symptoms. Persistent unilateral ptosis with fluctuating bulbar symptoms in an elderly patient, normal neuroimaging, and preserved limb strength should prompt consideration of myasthenia gravis despite an initial stroke pathway. As most cases classically present before the age of 50-60 years, this presentation in an 82-year-old man also illustrates very late-onset acetylcholine receptor antibody-positive disease. This case highlights that unilateral ocular involvement does not exclude myasthenia gravis and that close attention to fatigability and symptom evolution can prevent misdiagnosis and support timely, appropriate treatment.