Pseudomyasthenia resulting from a posterior carotid artery wall aneurysm: A novel presentation: Case report

OBJECTIVE AND IMPORTANCE: Painful oculomotor palsy can result from enlargem ent or rupture of intracranial aneurysms. The IIIrd cranial nerve dysfuncti on in this setting, whether partial or complete, is usually fixed or progre ssive and is sometimes reversible with surgery. We report an unusual oculom otor manifestation of a posterior carotid artery wall aneurysm, which mimic ked ocular myasthenia gravis. CLINICAL PRESENTATION: A 47-year-old woman developed painless, intermittent , partial IIIrd cranial nerve palsy. She presented with isolated episodic l eft-sided ptosis, which initially suggested a metabolic or neuromuscular di sorder. However, digital subtraction angiography revealed a left posterior carotid artery wall aneurysm, just proximal to the origin of the posterior communicating artery. INTERVENTION: The aneurysm was successfully clipped via a pterional craniot omy. During surgery, the aneurysm was observed to be compressing the oculom otor nerve. The patient's symptoms resolved after the operation. CONCLUSION: The variability of incomplete IIIrd cranial nerve deficits can present a diagnostic challenge, and the approach for patients with isolated IIIrd cranial nerve palsies remains controversial. Although intracranial a neurysms compressing the oculomotor nerve classically produce fixed or prog ressive IIIrd cranial nerve palsies with pupillary involvement, anatomic va riations may result in atypical presentations. With the exception of patien ts who present with pupil-sparing but otherwise complete IIIrd cranial nerv e palsy, clinicians should always consider an intracranial aneurysm when co nfronted with even subtle dysfunction of the oculomotor nerve.