title: Gaze-evoked tinnitus following acoustic neuroma resection: a de-afferentation plasticity phenomenon?
abstract: A review of the prevalence of gaze-evoked tinnitus in patients who have undergone acoustic neuroma resection was undertaken. The relationship of gaze-evoked tinnitus to tumour size, pre-existing tinnitus, side of the lesion or direction of eye gaze was also analysed. The design was a retrospective review of patients who underwent total unilateral translabyrinthine vestibular schwannoma resection by the senior author. Patients 1 year and 5 years following surgery were assessed. Results were obtained by either direct questioning in a clinical setting or via questionnaire. Data was collected on 36 subjects at an average of 14.6 months postoperatively (range 8-20 months) and on 32 subjects at an average 62 months postoperatively (range 56-68 months). Of the first group, 13 had evidence of gaze-evoked tinnitus (36%) compared with six (19%) of the second. The presence of preoperative tinnitus was a significant variable in univariate and multivariate analyses of the presence of postoperative tinnitus and postoperative gaze-evoked tinnitus. In a reduced model multivariate logistic regression using the two groups combined, the significant independent risk factors for gaze-evoked postoperative tinnitus were female sex (P = 0.046, odds ratio = 4.3), right side surgery (P = 0.02, odds ratio = 5.5) and pre-existing tinnitus (P = 0.008, odds ratio = 24.2). Gaze-evoked tinnitus is more common than previously reported in patients undergoing vestibular schwannoma resection. The underlying pathophysiology remains unclear but neural plasticity following unilateral de-afferentation remains a viable theory. The reduced prevalence over time suggests that this phenomenon may represent an active reinnervation process within the brain, which stabilizes with time. The significance of pre-existing tinnitus suggests that mechanisms of neural reorganization modify an existing physiological pathway. Further research is required into the longevity of this phenomenon, preferably with longitudinal studies.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, St Vincent's Hospital Darlinghurst, Australia. nbiggs@ozemail.com.au
authors.forename: N D W
authors.initials: ND
authors.lastname: Biggs
authors.forename: R T
authors.initials: RT
authors.lastname: Ramsden
mesh_terms: D000328:Adult; D000368:Aged; D001306:Auditory Pathways / Q000503:physiopathology; D005133:Eye Movements; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009464:Neuroma, Acoustic / Q000601:surgery*; D009473:Neuronal Plasticity; D011183:Postoperative Complications; D012189:Retrospective Studies; D012307:Risk Factors; D014012:Tinnitus / Q000209:etiology* / Q000503:physiopathology