Postoperative vertigo is one of the common complaints after cochlear implantation (CI). Recently, development of new electrode designs and minimally invasive surgery have enabled preservation of residual hearing. At our department, an atraumatic electrode, FLEXSOFTôí of MED-EL, is inserted via the round window approach (RWA) and dexamethasone is administered intraoperatively and postoperatively to preserve vestibular function, regardless of the level of residual hearing ability. This retrospective study was aimed at determining the frequency of equilibrium dysfunction after minimally invasive CI. Between April 2018 and March 2019, 10 adult patients underwent minimally invasive CI surgery at our institution. The equilibrium function in these patients was assessed based on the symptom of vertigo, nystagmus, results of the caloric reflex test, measurement of vestibular evoked-myogenic potential (VEMP), and static stabilometry, before surgery and at various intervals after the surgery. One year after the surgery, 1/10 patients (10ô) reported dizziness, and nystagmus was observed in 2/10 patients (20ô). There were no abnormal results of the caloric reflex test after the surgery (0/4 side). Examination of the ocular VEMP (oVEMP) showed abnormal values before surgery on all sides. Examination of cervical VEMP (cVEMP) showed abnormal values after surgery on 5/9 sides (56ô). In the static stabilometer test, there was no significant deterioration in either the Romberg's ratio of velocity with foam rubber or the foam ratio of velocity with eyes closed after the surgery. Our study showed that the functions of the saccule can become impaired after minimally invasive CI. cVEMP may be most sensitive for detection of problems after CI surgery, since the saccule is anatomically closer to the implanted cochlea as compared to other vestibular organs.
CITATION STYLE
Yokoi, J., Yanagisawa, S. G., Kakigi, A., Fujita, T., Iwaki, S., Kajimoto, Y., & Nibu, K. I. (2021). Vestibular function in minimally invasive cochlear implantation. Equilibrium Research, 80(1), 31–40. https://doi.org/10.3757/JSER.80.31
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