Tinnitus loudness in quiet and noise after resection of vestibular schwannoma.


OBJECTIVES: (1) To use a loudness model to assess the influence of loudness recruitment on estimates of the loudness of tinnitus obtained by loudness matching; (2) To compare the effect of background noise on the loudness of tinnitus for individuals who are unilaterally deaf after resection of vestibular schwannoma (VS) and those with idiopathic tinnitus. BACKGROUND: After translabyrinthine resection of VS, patients experience unilateral deafness and tinnitus in the operated ear. Most complain that their tinnitus is more bothersome in noisy environments, unlike those with idiopathic tinnitus. PARTICIPANTS: Unilaterally deaf individuals experiencing tinnitus as a consequence of VS surgery and a comparison group with idiopathic tinnitus. METHODS: Participants adjusted the level of a probe tone at the frequency where their hearing was best to match the loudness of their tinnitus in quiet; for VS participants, matches were made using a probe in the unaffected ear. Matches were then obtained in the presence of threshold-equalizing noise. RESULTS: For those with idiopathic tinnitus, the probe loudness level, calculated using a loudness model, was almost invariant with hearing loss at the probe frequency and was usually between 20 and 50 phons. For the VS group, the probe loudness level ranged from 6 to 51 phons. With increasing threshold-equalizing-noise level, the loudness match decreased slightly for the comparison group but increased significantly for the VS group. CONCLUSION: The tinnitus in quiet had a moderate loudness for both groups. Background noise slightly decreased tinnitus loudness for most participants with idiopathic tinnitus but increased tinnitus loudness for VS participants. We propose 2 possible mechanisms for the effect of noise in the VS group.