Internal carotid artery aneurysm with incomplete isolated oculomotor nerve palsy: a case report

Oculomotor nerve palsy is a common and well-described disease with diverse etiologies. Clinicians should quickly and correctly diagnose and treat oculomotor nerve palsy according to its characteristics and the accompanying symptoms and signs. Intracranial aneurysm is an important and frequent cause of oculomotor nerve palsy. Considering the catastrophic consequences of rupture, the possibility of an urgent, life-threatening disease should always be considered.

A 63-year-old Chinese woman presented with intermittent left ptosis and diplopia and painless incomplete oculomotor nerve palsy without pupil involvement. She manifested no mydriasis or extraocular muscle weakness, and the light reflex was normal. Other cranial nerves and somatosensory and somatomotor examinations were normal. The neostigmine experiment and electromyography were normal, so the diagnosis of myasthenia gravis was excluded. Brain magnetic resonance angiography showed a 4-mm aneurysm located at the cavernous segment of the left internal carotid artery. Unfortunately, the patient refused digital subtraction angiography and was discharged home without further treatment.

Neuroimaging must be performed to exclude intracranial aneurysms in oculomotor nerve palsy regardless of whether the pupils are involved, as aneurysm rupture carries substantial morbidity and mortality.