Aplasia of sigmoid sinus with high-lying jugular bulb.

A 25-year-o ld woman was admitted with a 20 year history of pulsatile tinnitus. She had been aware of " buzzing " in her right ear since she was a ch ild. There was no history of otalgia, hearing loss, nor ear discharge. Th e physical examination revealed a blue hypotympanic mass medial to an intact right tympanic membrane. Increasing the air pressure in the external canal failed to cause a blan ching of the mass (Brown sign) . There was no audible bru it. An audiogram showed a minimal low-toned ipsilateral conductive loss. Electronystagmorgraphy, posturography, and rotation testing were normal. Petrous pyramid tomography showed a large right jugular foramen but without any obvious bony erosion. CT and cerebral angiography failed to reveal any mass lesion or abnormality. Venous films were not obtained at angiography.