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Visual evoked potentials and magnetic resonance imagings of Tolosa–Hunt syndrome before and after steroid therapy

Tolosa–Hunt syndrome (THS) consists of painful ophthalmoplegia caused by cavernous sinus inflammation, and is responsive to steroid therapy. Magnetic resonance imaging (MRI) is of value in the diagnosis of this condition. As optic nerve involvement was mentioned in an early work on THS by Hunt et al. (1), longitudinal changes in the pattern-reversal, visual evoked potential (VEP) and MRI were examined in a patient with THS. In this case, the VEP before treatment was found to be prolonged and reduced in its P100 latency, although the optic nerve was both clinically and radiologically found to be intact. The patient, a 25-year-old Japanese woman, had no remarkable history. She presented with acute severe pain behind the left eye. She also showed mild diplopia while gazing laterally to the left, and was not aware of this symptom until pointed out by the physician. Ocular examination revealed slight paresis of the left 6th cranial nerve. No blepharoptosis was noted in either eye and both optic fundi had a normal ophthalmoscopic appearance. Visual acuity andGoldmann perimetry were normal on both sides, and all other neurological findings were within normal limits. The results of plain skull radiograph, computed tomography of the brain and the analysis of cerebrospinal fluid did not suggest a diagnosis. Furthermore, the relevant laboratory data were normal except for a slightly increased erythrocyte sedimentation rate. The initial T2-weighted coronal MRI using the spin echo method (TR 1⁄4 3300 ms, TE 1⁄4 88 ms) revealed an abnormal high-intensity area in the left cavernous sinus because it was being restricted by the intracavernous carotid artery (arrowhead) which was not adjacent to the left orbital apex and separated from the optic chiasm (Fig. 1, left). VEP of the left eye, with full field stimulation performed simultaneously with the initial MRI was prolonged and showed reduced P100 latency (Fig. 2, left). On the basis of a tentative diagnosis of THS, the patient was treated with oral prednisolone (1 mg/kg daily) for 3 weeks, which was gradually tapered off over the following 4 weeks. The steroid therapy dramatically improved her orbital pain and diplopia without any residual symptoms and signs.