Cochlear implant surgery and perioperative dizziness is associated with utricular hyperfunction

Abstract

BACKGROUND: Dizziness is a common perioperative complication after cochlear implantation (CI). To date, the exact cause behind this phenomenon remains unclear. There is recent evidence to suggest that otolith function, specifically utricular, may be affected shortly after CI surgery, however whether these changes are related to patient symptoms has not yet been investigated. OBJECTIVE: To determine whether CI surgery and perioperative dizziness is associated with changes on utricular function. METHODS: We performed an observational study on patients undergoing routine CI surgery. Utricular function was assessed using the Subjective Visual Vertical (SVV), and perioperative dizziness was determined using a questionnaire. The study followed patients before surgery and then again 1-day, 1-week and 6-weeks after implantation. RESULTS: Forty-one adult CI recipients participated in the study. The SVV deviated away from the operated ear by an average of 2.17° a day after implantation, 0.889° 1 week and –0.25° 6 weeks after surgery. Dizziness contributed to a tilt of 0.5° away from the implanted ear. These deviations were statistically significant. CONCLUSIONS: CI surgery causes utricular hyperfunction in the operated ear that resolves over 6 weeks. SVV tilts were greater in participants experiencing dizziness, suggesting that utricular hyperfunction may contribute to the dizziness.

Four-Point Impedance and Utricular Dysfunction Is Associated with Postoperative Dizziness after Cochlear Implantation

“…Although this paper’s findings provide further support for the notion that acute cochlear inflammation or endolymphatic hydrops may underlie SVV deviation and dizziness, we did not observe all the associations between 4PI, SVV, and dizziness that might have been expected if a simple relationship existed between these outcomes and the cochlear pathology. For example, unlike Truong and colleagues (19), we did not find that dizziness was related to greater SVV deviation away from the operated ear. Apart from differences in sample size, and methodological differences between this study and those of Bester et al (20), Razmovski et al (36), and Truong et al (19), another possible contributing factor may be differing sensitivities of each measurement or percept.…”

“…We also showed that SVV angle significantly deviated away from the operated ear at 1 day and 1 week, before returning to preoperative levels by 1 month. This finding is consistent with other studies showing similar results after cochlear implantation (19,28,29). However, the patient’s experiences of dizziness were not associated with a significantly different deviation in SVV angle.…”

“…The utricle is filled with endolymph and suspended within the vestibule on the membrana limitans, floating in perilymph (41). Thus, changes in the hydrostatic balance between these two fluid compartments could lead to bowing of the sensory cells, potentially resulting in an increase in the resting activity of utricular afferent neurons (19). Although a reduction in perilymph volume immediately after surgery might be expected, this seems unlikely to persist in the forthcoming weeks, when SVV deviation was found in this study.…”

“…Instead, this time course reflects that expected of endolymphatic hydrops. Therefore, the deviation in SVV angle away from the operated ear at 1 day and 1 week after surgery could arise from ipsilateral utricular hyperfunction caused by endolymphatic hydrops (19). Endolymphatic hydrops is a downstream consequence of labyrinthine inflammation.…”

“…Estimated SVV angle was standardized such that a positive angle indicated a deviation away from the operated ear. At each time interval, dizziness symptoms were classified using a diagnostic algorithm taken from Truong et al (19) (Supplementary Fig. 2, http://links.lww.com/MAO/B670).…”