Magnetic resonance imaging in acute optic neuropathy by sphenoidal mucocele.

A 45-year-old man suffered sudden visual loss with Marcus-Gunn pupil and a central scotoma in the right eye as evaluated by visual field examination. The patient's right visual acuity was 0.02 (0.08 x -4.5 D). T1-weighted magnetic resonance imaging (MRI) demonstrated a cystic lesion of high intensity in the right sphenoid sinus. Short T1 inversion recovery (STIR) images presented a cystic lesion of high intensity in the right sphenoid sinus. In addition, a ring-shaped high intensity signal was seen surrounding the right optic nerve. Post-contrast fat suppression T1-weighted images did not demonstrate any enhancement within the right optic nerve. After intranasal sphenoidectomy, good recovery of the right visual acuity was noted. On subsequent MRI, the cystic lesion in the sphenoid sinus disappeared. Also, the ring of high intensity surrounding the right optic nerve became unclear. It was thought that the ring of hyperintensity seen on the STIR images demonstrated cerebrospinal fluid in the dilated perioptic subarachnoid space. Therefore, these MRI findings suggested that the acute visual loss resulted from a disturbed blood supply to the optic nerve due to compression by the sphenoidal mucocele, and not due to an inflammatory process.