Electrically evoked auditory brainstem response-based evaluation of the spatial distribution of auditory neuronal tissue in common cavity deformities.
OBJECTIVE
In a common cavity (CC) deformity, the cochlea and vestibule are confluent to form a single cavity without internal architecture, and distribution of auditory neuronal tissue is unclear. The purposes of this study are to reveal the spatial distribution of auditory neuronal tissue in CC deformity using electrically evoked auditory brainstem response (EABR) during cochlear implantation.


METHODS
Retrospective case review.


METHODS
Cochlear implant (CI) center at a tertiary referral hospital.


METHODS
Five patients with CC deformity who underwent cochlear implantation and intraoperative EABR testing.


METHODS
Spatial distribution of electrodes that elicited an evoked wave V (eV) in EABR testing was evaluated in each CC deformity.


RESULTS
Electrically evoked auditory brainstem response testing demonstrated that electrodes attached on the inner wall of the anteroinferior cavity of the CC deformity successfully elicited a reproducible eV in all cases, and the latency of each eV was an approximately 4 ms, which is similar to those reported in patients without an inner ear malformation. Interestingly, in Case 1 with the lowest percentage of eV-positive electrodes (31.8%), CI-aided audiometric thresholds were changed, depending on the frequency allocation to eV-positive electrodes in the programming. Cochlear implant-mediated facial nerve stimulation was observed in 3 of 5 cases, and results of EABR testing were useful for optimizing the device program to decrease facial nerve stimulation without sacrificing CI-mediated auditory performance.


CONCLUSIONS
The results of EABR testing suggested that auditory neuronal elements are distributed to the anteroinferior part of CC deformity, mainly around or near the inner wall of the cavity. In cases with CC deformity, EABR testing is useful to achieve the optimal electrode array placement and to adjust programming parameters of the implanted device, which might be essential to maximize CI outcomes and to decrease facial nerve stimulation.
*Department of Otolaryngology, Kobe City Medical Center General Hospital; †Institute of Biomedical Research and Innovation; and ‡Clinical Laboratory, Kobe City Medical Center General Hospital, Kobe, Japan.
Hiroshi
H
Yamazaki
Yasushi
Y
Naito
Keizo
K
Fujiwara
Saburo
S
Moroto
Rinko
R
Yamamoto
Tomoko
T
Yamazaki
Ichiro
I
Sasaki
D000328:Adult; D000368:Aged; D003051:Cochlea / Q000002:abnormalities* / Q000294:innervation*; D019929:Cochlear Implantation / Q000379:methods; D003054:Cochlear Implants; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014722:Vestibule, Labyrinth / Q000002:abnormalities* / Q000294:innervation*