["Tram-track" sign and "donut configuration" in Tolosa-Hunt syndrome]

We report unique MRI abnormalities seen in a patient with Tolosa-Hunt syndrome (THS). A 60-year-old woman was admitted for left eye symptoms, including periorbital pain, numbness around the left eyebrow, blurred vision, delayed light reflex and impairment of abduction. Laboratory studies were unremarkable except for elevated erythrocyte sedimentation rates. T1-weighted MRI showed a mass lesion in the left orbital apex. Fat-suppressed T2-weighted MRI showed a hyperintense parallel linear lesion on the left optic nerve and a ring lesion around it, producing the "tram-track" sign on the axial view and the "donut configuration" on the coronal view. A diagnosis of THS was made, and corticosteroid therapy was started. Symptoms were improved rapidly, and MRI abnormalities disappeared. Reevaluation of MRI which had been taken at the previous episode of the right eye symptoms two years before also showed the "tram-track" sign and the "donut configuration" on the right. These signs are easy to be recognized and well reflect the stage of the disease. They are thus useful for diagnosing THS and evaluating the effect of the treatment. One should pay attention not only to the cavernous sinus and orbital apex, but also to the optic nerve for the MRI diagnosis of THS.