Natural History of Hearing Deterioration in Intracanalicular Vestibular Schwannoma BACKGROUND: Intracanalicular vestibular schwannomas have a range of treatment options that can preserve hearing: microsurgery, stereotactic radiotherapy, and con- servative observation. OBJECTIVE: To evaluate the natural course of hearing deterioration during a period of conservative observation. METHODS: A retrospective case review was performed on 47 patients with a unilateral intracanalicular vestibular schwannoma. Evaluation of growth was monitored by repeat MRI scanning. Repeated pure-tone and speech audiometry results were evaluated for subgroups of patients showing growth or no growth and by subsite location of tumor in the internal auditory canal. RESULTS: Patients had a mean follow-up of 3.6 years. Over the entire population, the pure-tone average thresholds at 0.5, 1, 2, and 3 kHz and the word recognition scores both significantly deteriorated from 38 to 51 dB HL, and from 66% to 55%, respectively. Overall, 74% of subjects with good hearing, according to the 50/50 rule, maintained hearing above this rule. There were no significant differences in hearing loss by subsite in the internal auditory canal (porus, fundus, central) or by growth status (stable, growing, shrinking). Only 6 patients showed a large hearing change. This happened early during follow-up, with relatively stable hearing after this. CONCLUSION: Hearing will deteriorate in some intracanalicular vestibular schwanno- mas, regardless of tumor growth. Hearing deterioration, if on a large scale, most likely occurs early in follow-up. The present results using conservative management in these tumors appear similar to those reported for stereotactic radiotherapy or microsurgery. KEY WORDS: Acoustic neuroma, Hearing, Hearing preservation, Intracanalicular, Microsurgery, Stereotactic radiotherapy, Vestibular schwannoma Neurosurgery 68:68–77, 2011 DOI: 10.1227/NEU.0b013e3181fc60cb www.neurosurgery-online.com A vestibular schwannoma (often used syn- onymously with the term acoustic neu- roma) is a benign tumor arising from the Schwann cell covering of the eighth cranial nerve. These tumors often first present with asymmetric hearing loss. Other symptoms may be tinnitus, aural fullness, poor speech discrimination, imbalance, or, rarely, vertigo. Varied explanations for the etiology of hearing deterioration in patients with vestibular schwannomas, including tumor- induced expansion with subsequent increase of pressure in the internal auditory canal, cochlear hair cell loss, vascular compromise, and a change in inner ear fluid composition, have been reported. 1,2 As accessibility to MRI scanning has im- proved, the number of patients with a diagnosis of vestibular schwannoma has increased, and the size of tumor at diagnosis appears to be smaller. In recent years, the management of vestibular schwannomas has become controversial, because several different treatment strategies have been proposed. Intracanalicular tumors present several valid management choices. Their small size allows for the possibility of hearing preservation after sur- gery, but also for policies of conservative Ronald J. E. Pennings, MD, PhD* David P. Morris, MBBS, FRCS (ORL-HNS)* Linda Clarke, RN† Stefan Allen† Simon Walling, MBChB, FRCSC* Manohar L. Bance, MB, MSc, FRCSC* *Division of Otolaryngology – Head & Neck Surgery; and †Division of Neuro- surgery, Department of Surgery, Dalhou- sie University, Halifax, Nova Scotia, Canada Correspondence: Ronald Pennings, MD, PhD, Dalhousie University, Department of Surgery, Division of Otolaryngology – Head & Neck Surgery, 1278 Tower Road, 3184 Dickson Building, VGH Site, QEII HSC, Capital Health, B3H 2Y9, Halifax, Nova Scotia, Canada. E-mail: r.pennings@kno.umcn.nl Received, September 9, 2009. Accepted, April 30, 2010. Copyright ª 2010 by the Congress of Neurological Surgeons ABBREVIATIONS: ANOVA, analysis of variance; HL, hearing level; IAC, internal auditory canal; PTA, pure-tone average; SRT, stereotactic radiotherapy; WRS, word recognition score 68 | VOLUME 68 | NUMBER 1 | JANUARY 2011 www.neurosurgery-online.com RESEARCH—HUMAN—CLINICAL STUDIES TOPIC Research—Human—Clinical Studies Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited.