title: Effect of cochlear implantation on horizontal semicircular canal function.
abstract: The objective of this study was to assess the influence of a cochlear implant (CI) on horizontal semicircular canal (hSCC) function, to test the correlation with symptomatic vertigo and to identify possible risk factors for a postoperative vestibular impairment. In a prospective observational study design, forty-seven adult patients who had undergone cochlear implantation at Cochlear Implant Center at a tertiary referral university hospital, Munich, between 2003 and 2007, were studied. Postoperative vertigo symptoms were assessed using a questionnaire followed by a structured interview. Patients were subjected to caloric and rotational chair vestibular function tests pre- and postoperatively. The CI operation was performed with a retroauricular transmastoidal approach by three different surgeons. Thirty-six implants were Cochlear Nucleus 24 devices and 11 implants were MedEl devices. Twenty-one (45%) patients reported vertigo symptoms after CI. Functional testing of the hSCC yielded valid results in 45 of the 47 patients. Thirty-two percent of patients had a substantially reduced hSCC function after CI. Responses of caloric irrigation showed a significant worsening postoperatively in the CI ears. No direct correlation between a decrease in caloric response and risk of postoperative vertigo symptoms could be established. For the criteria age, sex, implant type, surgeon, cause of deafness, petrous bone CT findings and preoperative vertigo, there were no significant differences between the patients with and the patients without postoperative vertigo. Besides morphological changes, a cochlear implantation also causes functional damage of vestibular parts of the labyrinth. Our study showed a significant worsening of the caloric response. However, this alteration did not lead to vertigo complaints in all patients. It is therefore presumed that additional damage to sensory or visual afferents and central vestibular compensatory mechanisms play a role.
authors.affiliation: Department of Oto-Rhino-Laryngology, Head and Neck Surgery, Ludwig-Maximilians-University Munich, Marchioninistrasse 15, 81377, Munich, Germany. eike.krause@med.uni-muenchen.de
authors.forename: Eike
authors.initials: E
authors.lastname: Krause
authors.forename: Julia P R
authors.initials: JP
authors.lastname: Louza
authors.forename: John-Martin
authors.initials: JM
authors.lastname: Hempel
authors.forename: Juliane
authors.initials: J
authors.lastname: Wechtenbruch
authors.forename: Tobias
authors.initials: T
authors.lastname: Rader
authors.forename: Robert
authors.initials: R
authors.lastname: Gürkov
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002150:Caloric Tests; D019929:Cochlear Implantation / Q000379:methods*; D003054:Cochlear Implants / Q000009:adverse effects*; D003638:Deafness / Q000209:etiology / Q000601:surgery*; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012665:Semicircular Canals / Q000293:injuries*; D011795:Surveys and Questionnaires; D014717:Vertigo / Q000209:etiology* / Q000503:physiopathology; D015837:Vestibular Diseases / Q000209:etiology* / Q000503:physiopathology; D014724:Vestibular Function Tests; D014722:Vestibule, Labyrinth / Q000293:injuries*