Audiovestibular findings and location of an acoustic neuroma

Forty-one patients with unilateral acoustic neuroma (AN) were diagnosed by magnetic resonance imaging (MRI) between 1992 and 1997. All cases were anal yzed with respect to tumor location and the results of audiometric examinat ions, auditory brainstem response (ABR) testing, and electronystagmography (ENG), Tumor location was determined by MRI and cases were divided into int racanalicular and extracanalicular sites. Intracanalicular tumors were sign ificantly smaller than the extracanalicular ones The pure-tone hearing thre sholds were better in ears with intracanalicular lesions than in those with extracanalicular ones. Respectively, speech reception thresholds were 33 d B and 45 dB, and speech discrimination scores 79% and 65%. ABR was abnormal in 98% of ANs, but was insufficient for determining tumor location. The EN G pursuit test was more frequently nor mal and the caloric side difference was smaller in ears with intracanalicular than extracanalicular AN. These f indings show that the results of pure-tone and speech audiometry and ENG ar e better in ears with intracanalicular AN, while ABR results are similar re gardless of tumor location.