Abstract
The authors reviewed 82 patients with cerebellopontine angle lesions, who were examined audiologically and neurotologically at the University of Tokyo from April 1977 to March 1987. Acoustic tumors (AT) were diagnosed in 58. The others had meningiomas, epidermoids, aneurysms, etc. Nearly all (93.1 %) of those with acoustic tumors had sensorineural hearing loss. Ten patients (17.2%) had an interaural difference of hearing levels of up to 25dB at 500, 1000 and 2000Hz, which was defined as a slight interaural difference and only four (6.9%) had hearing levels of 25dB or better at 500, 1000 and 2000Hz, which was defined as a slight hearing impairment. On the other hand, in those with other lesions, hearing acuity was preserved in fifty percent. Sixteen (66.7%) and fourteen (58.3%) had slight interaural differences of hearing levels and had slight hearing impairment. The results of physiological tests-auditory brainstem response (ABR), stapedial reflex (SR), and caloric test-revealed that ABR is sensitive in patients with AT and other tumors or abnormalities. Caloric test and SR showed good sensitivity in AT but not in other tumors or abnormalities. These findings may help in the differential diagnosis of AT and other tumors or abnormalities.
The authors conclude that ABR has good sensitivity for cerebellopontine angle lesions with slight hearing impairment and that the use of SR and caloric test together with ABR may enable us to distinguish AT from other tumors or abnormalities.
