Cochlear Implantation in Cases of Inner Ear Malformation: A Novel and Simple Grading, Intracochlear EABR, and Outcomes of Hearing

Abstract

Objective: To propose a simple grading of inner ear malformation (IEM) and investigate intracochlear electrical auditory brainstem response (EABR) and outcomes for hearing in terms of the novel grading system. Study Design: Retrospective case review. Setting: Tertiary referral center. Patients: Sixty patients with IEMs who received cochlear implants. Intervention: Grading according to observation of modiolus deficiency and/or internal auditory canal (IAC) cochlear nerve deficiency (CND). Main Outcome Measure: Intracochlear EABR and categories of auditory performance (CAP) scores were assessed; children in school were categorized according to the type of school attended. Results: Among 60 patients, 38% were classified as Grade I (modiolus present + normal cochlear nerve), 22% as grade II (modiolus deficiency + normal cochlear nerve), 33% as grade III (modiolus present + IAC CND), and 7% as grade IV (modiolus deficiency + IAC CND). During the operation, 93% of Grade I, 36% of Grade II, 23% of Grade III, and 50% of Grade IV patients showed typical EABR waves. CAP scores of 4 or more were obtained from 91% of Grade I, 62% of Grade II, 35% of Grade III, and 25% of Grade IV. Whereas none of children in Grades III and IV entered main stream school, 55% of Grade I and 25% of Grade II entered mainstream schools. Conclusions: Outcomes of hearing with cochlear implantations in IEM children depend on the severity of IEM and IAC CND. Our novel grading of IEM is simple and can be useful for understanding the severity of IEM.

Intraoperative EABR Testing Predicts Strength of Cochlear Implant Stimulation Optimized After Long-Term Use in Pediatric Malformation Ears

“…Most deaf children without malformation exhibited eV on the initial activation of the CI (19), whereas malformation ears often failed to show eV (7,8,20). The IP-2, IP-1, CC, and CND groups showed 100, 85.0, 81.8, and 54.8% of the eV-positive rate, respectively, consistent with these previous studies.…”

“…Like pediatric CI users without malformation, objective measurements during cochlear implantation, such as electrically evoked compound action potential (ECAP) and electrically evoked auditory brainstem response (EABR), might help optimize CI stimulus in the malformation ears. ECAP was detected in only 25% of the malformed ears (5), whereas positive EABR was reported in 50% of CND cases and greater than 75% of all malformed ears (5–8), suggesting that EABR rather than ECAP is more appropriate as an objective measurement for the malformed ears. These studies used intraoperative EABR testing to predict postoperative CI outcomes but did not compare the EABR results and strength of postoperative CI stimuli in malformation cases.…”

A 3-Year Follow-Up and Radiological Analysis of Cochlear Implantation Patients with Cochlear Nerve Deficiency and Modiolar Deficiency-Type Malformations

“…Due to the limited number of cases, previous studies have reported the CI outcomes of CND patients without grouping them according to cochlear malformations (4,5,10). To take both the CN and cochlea into consideration, Minami et al (11) categorized patients into four grades according to the observation of modiolar deficiency and/or CND: grade I (present modiolus + normal CN) patients had significantly greater CAP scores than grade II (deficient modiolus + normal CN), grade III (present modiolus + CND) and grade IV (deficient modiolus + CND) patients. Approximately 7% of patients had CND combined with modiolar deficiency-type malformations, and only 25% of them achieved CAP scores of 4 or more.…”