Sixth nerve palsy as the presenting symptom of metastatic colon carcinoma

Isolated cranial mononeuropathies in patients over 50 years of age most commonly result from microvascular ischemic demyelination. A 51-year-old female without vasculopathic risk factors presented with isolated sixth nerve palsy. Magnetic resonance imaging (MRI) of the brain and orbits revealed a cavernous sinus lesion that was diagnosed as a meningioma. Laboratory tests showed abnormal liver function, and an abdominal computerized tomogram demonstrated an obstructive colonic mass with liver metastasis. The pathology tests of specimens taken during a laparotomy diagnosed colon adenocarcinoma. The MRI interpretation was changed to cavernous sinus metastasis from a primary adenocarcinoma of the colon. This case had common cranial nerve symptoms but with a very rare etiology, emphasizing the importance of a high index of suspicion of remote origins in patients with isolated sixth nerve palsy and no atherosclerotic risk factors.