Unusual presentation of an isolated III Cranial Nerve palsy from brain metastasis

Isolated 3rd cranial nerve (CN) palsy is a rare presentation of brain metastasis. It is more commonly associated with other neurologic conditions such as myasthenia (MG), diabetic neuropathy, multiple sclerosis (MS), posterior communicating artery aneurysm (PCOM) and trauma. Asymptomatic character or unspecific symptoms related to an occult malignancy often times make the diagnosis and work-up for a third nerve palsy challenging. Our case illustrates an isolated 3rd CN palsy from brain metastasis secondary to a poorly differentiated sarcomatoid lung carcinoma detected in a diagnostic process initiated by a neuro-ophthalmologic examination.