Nasopharyngeal carcinoma presenting as a sixth nerve palsy and Horner's syndrome.

The combination of a sixth nerve palsy and ipsilateral Horner's syndrome localises the disease process to the posterior cavernous sinus and can be a result of various pathologies in this region. A 74-year-old Chinese woman presented with a 9-month history of binocular horizontal diplopia worse when looking left. She was found to have a left sixth nerve palsy and Horner's syndrome and MRI revealed an enhancing soft tissue mass in the nasopharynx with involvement of the bones of the skull base and invasion of the left cavernous sinus. Endoscopic biopsy of the mass confirmed the diagnosis of non-keratinising squamous cell carcinoma, which was Epstein-Barr virus positive. She was treated with radiation therapy. Patients with a sixth nerve palsy and ipsilateral Horner's syndrome should have urgent neuroimaging with careful attention to the cavernous sinus since sympathetic fibres join the sixth nerve for a short distance in this location.