Tolosa-Hunt syndrome: focus on MRI diagnosis.

Experience with modern neuroimaging techniques, computed tomography (CT) and magnetic resonance imaging (MRI) scans, in the diagnosis of Tolosa-Hunt syndrome (THS) is reviewed. Conventional CT scan remains normal in about two-thirds of these patients. In the reported 22 patients meeting the IHS criteria for a THS diagnosis on whom an MRI study was performed, MRI revealed a convex enlargement of the symptomatic cavernous sinus by an abnormal tissue isointense with gray matter on short TR/TE images and isohypointense on long TR/TE images. This abnormal tissue markedly increases in signal intensity after contrast injection. MRI seems also to be the ideal technique to follow progressive resolution of the abnormal tissue after steroids. Therefore, normal MRI would probably exclude THS, whereas in the appropriate clinical setting of steroid-responsive painful ophthalmoplegia, MRI showing the cavernous sinus abnormality described here suggests a diagnosis of THS. From these data, we propose that the fourth IHS criterion for THS diagnosis, "Exclusion of other causative lesions by neuroimaging and (not compulsory) carotid angiogram" should be changed to "Finding by MRI of specific cavernous sinus abnormalities (with the characteristics described herein) which slowly resolve with steroid treatment".