Positional vertigo and cochlear implantation.

OBJECTIVE: To identify patients developing positional vertigo after cochlear implantation. STUDY DESIGN: Prospective study on a cohort of patients undergoing cochlear implantation. SETTING: Academic tertiary referral center. PATIENTS: The study included 70 consecutive patients who underwent vestibular evaluation before and after cochlear implantation. INTERVENTION: Medical record review. MAIN OUTCOME MEASURE: Recorded vestibular symptoms after cochlear implantation. Patients with positional vertigo were considered case subjects, whereas those without vestibular symptoms were considered case controls. RESULTS: Benign paroxysmal positional vertigo (BPPV) occurred in 8 patients (on the cochlear implant [CI] side in 7 patients, and in the other ear in 1). One patient had BPPV of the lateral semicircular canal on the implanted side, and 7 patients had BPPV of the posterior semicircular canal (on the same CI side in 6 patients, and on the opposite side in 1), which were detected and presented during the last examination. In 5 patients, the onset of symptoms varied from 7 to 130 days after implant activation; in 2 patients, the onset occurred before activation. CONCLUSION: Three different mechanisms are proposed for the occurrence of BPPV in patients with CI. The first focuses on the fall of bone dust particles into the cochlea during cochleostomy. In the second, the vibration caused by drilling the cochlea would be sufficient to dislodge otoconia into the labyrinth. The third hypothesis suggests dislodging of an otolith because of the electric stimulation. In our patients, conservative approaches have been used with a minimal invasive cochleostomy and without perilymph suction. Thus, the vibratory trauma affecting the cochlea during cochleostomy seems to play a fundamental role in the development of paroxysmal vertigo in patients with implant.

Vestibular impairment and cochlear implantation.

CONCLUSION: Cochlear implantation (CI) may induce vestibular impairment soon after surgery as well as after implant activation. This impairment seems to be independent from the cause of deafness and can be considered a possible complication from the intra-operative trauma and, to minor degree, from the ongoing electric stimulation. It would also seem that vestibular damage occurs independently from the likelihood of post-operative hearing deterioration. In unilateral selected CI cases, vestibular examination can be proposed as additional pre-operative exam for selection of the ear to be implanted. OBJECTIVES: This study has been planned in order to get evidence of eventual impairment of the vestibular apparatus after cochlear implantation as well as to verify whether the impairment could be related to different variables, such as cause of deafness, concomitant hearing deterioration, surgical trauma and duration of electrical stimulation. METHOD: 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.