The Effects of Cochlear Implantation on Vestibular Function

Abstract

Objective Determine the risk posed by cochlear implantation (CI) to the labyrinth. Study Design Prospective cohort study. Setting Academic tertiary referral center. Patients Thirty-six ears belonging to 35 adult CI candidates (mean: 46, range: 23–69 years old). Intervention Cochlear implantation. Main Outcome Measures Vestibular function was assessed using the quantitative 3D head impulse test (qHIT), clinical head impulse test (cHIT), post-headshake nystagmus (HSN), caloric electronystagmography (ENG), vestibular-evoked myogenic potentials (VEMP), dynamic visual acuity (DVA), and Dizziness Handicap Inventory (DHI). Results All 36 ears were tested using qHIT before CI, and 28 ears were tested 4–8 weeks after CI. Quantitative HIT showed 1/28 of ears suffered reduced function. Clinical HIT was 44% sensitive and 94% specific for identification of severe-to-profound vestibular hypofunction confirmed by qHIT. HSN was unchanged in 11/11 subjects. New hyporeflexia was found in 1/16 of ENG-tested ears. VEMP showed either a disappearance of response or an increase in threshold by >10dB in 5/16 ears. Passive DVA showed no change in 16/16 ears. DHI scores worsened in 3/28 and improved in 4/28 subjects. Conclusions Although small, the observed rate of labyrinthine injury was comparable to that for other risks of CI. Thus, it is important to educate CI candidates about possible risk to balance function, particularly when CI of an “only balancing ear” is contemplated. Clinical HIT is useful for detecting severe high-frequency vestibular hypofunction and should be part of the pre-CI physical examination.

Vestibular and taste disorders after bilateral cochlear implantation

“…This could be due to a bilateral impairment of vestibular receptors even when this was not always clearly reflected in the results of our neurootological test battery. This is in line with Melvin [7] and Enticott [5] whose data also show a poor correlation between the postoperative, subjective rating of vertigo and objective neurootological findings. It should be considered that the utricular maculae were not tested and could have been potentially impaired as well [22].…”

“…In general, complications in cochlear implantation are rare nowadays because the procedure has been standardized to minimize any patient's risk. Specific surgical complications (apart from inflammation and bleeding) reported in the literature include an electrode dislocation, facial nerve lesion, but also dizziness and taste disorders [4][5][6][7][8]. The latter potential risks of vestibular and/or taste impairment have to be carefully discussed with the patients when a bilateral implantation is considered.…”

Ocular and cervical vestibular-evoked myogenic potentials in children with cochlear implant

“…The data of oVEMPs after CI have not been reported yet. The rate of postoperative hypofunction was reported to be 13-86% in cVEMP (Todt et al, 2008;Krause et al, 2009;Licameli et al, 2009;Melvin et al, 2009;Krause et al, 2010;Wagner et al, 2010). Jin et al (2006)reported a response rate change in children with severe sensorineural hearing loss: seven of 12 patients presented normal cVEMPs before CI, but all disappeared after CI.…”

“…Todt et al (2008) found a 62.9% response rate of the cVEMP in 39 patients preoperatively, but 13 (21.0%) patients lost their normal responses of cVEMP postoperatively. Melvin et al (2009) reported a deterioration of cVEMP in five of 16 ears (31%) after CI. A cVEMP disappearance rate of 20% after surgery was found by Licameli et al (2009).…”

“…Such injuries included collapse, hydrops, fibrosis, and sensory cell reduction of the organ (Tien and Linthicum, 2002;Handzel et al, 2006). The damage rate of the saccule was reported to range from 21% to 100% (Jin et al, 2006;Todt et al, 2008;Licameli et al, 2009;Melvin et al, 2009;Krause et al, 2010). Several pathologic factors could contribute to the damage.…”