Effectiveness of cochlear implant in inner ear bone malformations with anterior labyrinth involvement

Objective: To study electrical stimulation, auditory functionality, and language development in patients with inner ear malformations involving the anterior labyrinth who underwent cochlear implantation.

Study design: Retrospective case review.

Setting: Reference hospital for cochlear implantation.

Patients: Review of 14 cases of severe hearing loss with major (common cavity deformity and cochlear hypoplasia) or minor (e.g., incomplete partition and basal turn aplasia) malformations.

Interventions: After cochlear implantation, data were gathered on the threshold (THR) and maximum comfort level (MCL) of the electrical stimulation and the number of functioning electrodes. Auditory responses to speech (EARS protocol) subtests were used to evaluate auditory functionality and language acquisition at 6, 12, and 24 months post-implantation. Tests used were: LIP profile, MTP (3, 6 and 12 words), OLD (open set test) and CLD (close set test). Results were compared with findings in a control group of 28 cochlear implantation patients without these malformations and with congenital hearing loss.

Results: The mean THR was 11.02μC in patients with malformations versus 3.5μC in those without, a significant difference. The THR also significantly differed between groups with major and minor malformations. Fewer functioning electrodes were used in patients with malformations. Auditory functionality scores were best in controls than in patients with malformations, who scored ≤50%, finding the lowest scores in those with major malformations.

Conclusion: Patients with inner ear malformations undergoing cochlear implantation require greater stimuli to obtain an auditory response and have worse auditory functionality outcomes; these differences are greater in those with major versus minor malformations Nevertheless, cochlear implantation appears to be beneficial for all patients with these malformations to a greater or lesser extent.