Critical bandwidth in patients with acoustic neuroma.

Eleven patients with verified acoustic neuroma had critical band estimation performed by the method of loudness summation using noise bands centered around 1 kHz. The normal loudness difference between broad band noise and narrow band noise was reduced at all levels except the highest. Judged as single individuals, 9 of the 11 patients had a normal critical band. The pooled data indicated a normal critical band, both in patients with hearing loss less than 50 dB HL and in patients with hearing loss greater than or equal to 50 dB HL. The results are similar to those obtained in patients with Ménière's disease (Bonding, 1978c) and thus CB-measurements cannot be utilized for differentiating between cochlear and retrocochlear lesions. However, at the highest test levels applied the loudness difference between broad band noise and narrow band noise appeared to have some correlation to the presence or absence of recruitment.