Delayed hearing loss following vestibular schwannoma surgery: Behavioural and electrophysiological responses in the early postoperative period

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Audiology
Degree name
Master of Audiology
Publisher
University of Canterbury. Communication Disorders
Journal Title
Journal ISSN
Volume Title
Language
Date
2008
Authors
Feldman, Melanie Blair
Abstract

Some patients suffer hearing loss in the early postoperative period following vestibular schwannoma (VS) excision despite having intact hearing immediately after surgery. As this phenomenon has rarely been documented or described, the putative mechanism remains vague. The objective of the current study was to document the patterns of change in behavioural and electrophysiological responses in patients following VS surgery to better describe the phenomenon of delayed hearing loss. In particular, we aimed to determine whether the impairment that eventually leads to delayed hearing loss is neural or cochlear in origin.

Auditory function was monitored in six adult patients who underwent surgery at Christchurch Public Hospital for excision of unilateral vestibular schwannoma through the retrosigmoid approach. Patients were assessed pre- and postoperatively by puretone audiometry, speech audiometry, tympanometry, distortion product otoacoustic emissions (DPOAEs), and auditory brainstem response (ABR). When measurable hearing was demonstrated postoperatively, pure-tone audiometry, speech audiometry and ABR were assessed at 24 hour intervals following surgery. Transtympanic electrocochleography (ECochG) was carried out if wave I of the ABR was lost during the postoperative period. Postoperative monitoring revealed that 4 patients suffered permanent anacusis and the remaining 2 patients had permanent hearing preservation. There were no patients who experienced delayed hearing loss in the early postoperative period. A phenomenon similar to delayed hearing loss was observed in case 2 who demonstrated loss of ABR wave I on the 7th postoperative day. Postoperative ECochG recorded in this case showed an enhanced negative SP on the operated side. The findings of this study are discussed in detail with particular reference to the underlying pathophysiology.

Description
Citation
Keywords
Audiology, vestibular schwannoma, acoustic neuroma, electrophysiology
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
Rights
Copyright Melanie Blair Feldman