Vestibular impairment and cochlear implantation

Abstract

Charts from two different populations of implantees have been reviewed, 21 from a prospective, 72 from a retrospective study, respectively. All the patients were implanted with Clarion(R) devices of different generation. Vestibular testing was based on rotatory, caloric (when possible) and stabilometric measurements, which were carried out pre-operatively and at the following different times: 5 weeks after CI surgery, and 30, 60 and 90 days after CI activation. Hearing thresholds were also assessed in those patients who showed signs of vestibular impairment as well as in a group of patients without vestibular disorders (control). Patients belonging to the retrospective group were all asked to fill a questionnaire regarding their balance condition. Results. In 14.3% of the prospective study group, a grade I and II spontaneous nystagmus was evidenced pre-operatively and remained unchanged during the whole assessment period. A grade II spontaneous nystagmus was present in 3 patients (21.4%) of the same group after surgery. In the immediate post-operative period, vestibular impairment was displayed as true rotational vertigo in 21.4% and unsteadiness in 42.8% of the study group. Severe unsteadiness was present during the first 2 days after activation in 14.3% of the subjects. In 21.4% of the patients a VPPB episode occured. In the retrospective study group, 26.4% of the subjects referred pre-operative dizziness and 25 patients (34.7%) referred immediate post-operative vertigo episodes, which remained in a milder form after CI activation in 12% of them. The hearing threshold showed to deteriorate in both vestibular-impaired and control CI population without significant difference.

Dexamethasone Is One of the Factors Minimizing the Inner Ear Damage from Electrode Insertion in Cochlear Implantation

“…There have been several studies about the steroid effect on HP after CI [Causon et al, 2015;Chang et al, 2009;Rajan et al, 2012], which was universally recognized. In case of vestibular preservation by steroid application, a change of vestibular function after CI was reported in several studies [Filipo et al, 2006;Katsiari et al, 2013;Meli et al, in press;Robard et al, 2015] but the evidence and the accurate mechanism of preservation effect were still not corroborated. Further research has been ongoing about several issues: the type of steroid, the method of use, timing of application, and the extent of inner ear penetration [Chandrasekhar, 2001;Chang et al, 2009;Mikulec et al, 2009;Rajan et al, 2012;Salt, 2010;Salt et al, 2011;Zou et al, 2010].…”

The Effects of Cochlear Implantation on Vestibular Function

“…When assayed using ENG testing, 0-43% of implanted ears exhibited a decrease in horizontal semicircular canal (SCC) function (2,3,(5)(6)(7)(14)(15)(16)(17)(18)(19)(20). Rotary chair testing revealed that 20-38% of implanted patients had a significant decrease in vestibular function after CI (18,19). OVAR revealed no change in vestibular function (19) after CI in one study.…”

“…Caloric stimulus on ENG testing is roughly equivalent to a 0.001-0.01 Hz head rotation (for which horizontal SCC input contributes minimally to gaze stabilization in daily life). Similarly, rotary chair testing probes the low-to mid-frequency band of the VOR response (~0.1-1 Hz) (15,18,19) leaving untested responses to the higher frequency (~1-16 Hz) components of head movement for which only the VOR can stabilize gaze (23,24). Extrapolating results of a single vestibular test to all vestibular endorgans and across the entire range of physiologically relevant stimuli is analogous to characterizing hearing using only a single pure-tone threshold while ignoring the remainder of the spectral range of normal hearing.…”

Methylprednisolone Applied Directly to the Round Window Reduces Dizziness after Cochlear Implantation: A Randomized Clinical Trial

“…Hearing can be near normal in the low frequen-Enticott/Eastwood/Briggs/Dowell/ O'Leary Audiol Neurotol 2011;16:289-303 290 rates of preservation are achieved in the immediate postoperative period [Filipo et al, 2006;Gantz et al, 2005;Gstoettner et al, 2006;Woodson et al, 2010].…”