Optic nerve MRI enhancement in posterior ischaemic optic neuropathy due to internal carotid artery dissection.

Posterior ischaemic neuropathy (PION) is characterized by infarction in the retrobulbar optic nerve. A 73-year-old man suddenly experienced blurred vision in his left eye and intermittent weakness in his right hand. He had visual defects of superior lateral quarter and inferior medial quarter areas in the left eye. Gadolinium-enhanced magnetic resonance imaging (MRI) revealed segmental enhancement in the left optic nerve. A cerebral angiogram showed a left internal carotid dissection (ICD). He did not have fever, and his laboratory and cerebrospinal fluid tests were normal. These findings were suggestive of PION associated with ICD. No reports of PION caused by ICD has been reported and his is the first case in which MRI showed optic nerve enhancement due to ICD.