["High jugular bulb": clinical feature, radiographical findings and differential diagnosis, a case report].

Anatomically, the top portion of the jugular bulb lies just below the floor of the hypotympanum. In rare instances, it can protrude upward and elevate the floor of the hypotympanum thus placing it in the middle ear. Such a case is called high jugular bulb. This anatomical variation has been found in 3.5% to 6% of the temporal bones studied in several reports. But, clinically, only 43 cases have been reported, because in most cases they are asymptomatic. A 17-year-old female was hospitalized with right hearing disturbance and dizziness. Neurootological examination revealed sensory neuronal hearing disturbance. A caloric test was scaled out. Axial bone window CT scan demonstrated an enlarged jugular bulb and an extended upward projecting hypotympanum. MRI indicated flow void in the same region. Retrograde jugulography has been the most useful method for diagnosis but we were able to diagnose it by noninvasive MR angiography. High jugular bulb is an unfamiliar disease entity for neurosurgeons, but we should remember that it is one of the differential diagnosis for c-p angle regions or jugular foramen regions.