The evidence base for the application of contralateral bone anchored hearing aids in acquired unilateral sensorineural hearing loss in adults.

. Acquired unilateral sensorineural hearing loss reduces the ability to localize sounds and to discriminate in background noise. . Four controlled trials attempt to determine the benefit of contralateral bone anchored hearing aids over contralateral routing of signal (CROS) hearing aids and over the unaided condition. All found no significant improvement in auditory localization with either aid. Speech discrimination in noise and subjective questionnaire measures of auditory abilities showed an advantage for bone anchored hearing aid (BAHA) > CROS > unaided conditions. . All four studies have material shortfalls: (i) the BAHA was always trialled after the CROS aid; (ii) CROS aids were only trialled for 4 weeks; (iii) none used any measure of hearing handicap when selecting subjects; (iv) two studies have a bias in terms of patient selection; (v) all studies were underpowered (vi) double reporting of patients occurred. . There is a paucity of evidence to support the efficacy of BAHA in the treatment of acquired unilateral sensorineural hearing loss. Clinicians should proceed with caution and perhaps await a larger randomized trial. . It is perhaps only appropriate to insert a BAHA peg at the time of vestibular schwanoma tumour excision in patients with good preoperative hearing, as their hearing handicap increases most.