Cochlear Implantation in a Child With Arnold-Chiari Syndrome, Severe Inner Ear Malformations, and Cochlear Nerve Hypoplasia: A Case Report.

BACKGROUND Arnold-Chiari syndrome is a congenital malformation of the posterior cranial fossa associated with neurological and otoneurological abnormalities, including hearing loss of variable severity. Cochlear implantation in patients with complex central nervous system malformations remains challenging due to uncertain auditory outcomes. This study aimed to evaluate the feasibility and early outcomes of cochlear implantation in a child with Arnold-Chiari syndrome and severe bilateral inner ear malformations. CASE REPORT A 1.5-year-old girl with Arnold-Chiari malformation, hydrocephalus, spina bifida, and profound bilateral sensorineural hearing loss was evaluated for cochlear implantation. Imaging studies revealed severe bilateral inner ear malformations, including cochlear hypoplasia, accompanied by multiple intracranial abnormalities. Despite early hearing aid use, auditory development remained limited. The patient underwent left-sided cochlear implantation with a MED-EL SYNCHRONY 2 device using a standard electrode array. Intraoperatively, significant cerebrospinal fluid leakage ("gusher") occurred during cochleostomy and was successfully controlled using autologous tissues and tissue adhesive. Twelve months after implantation, follow-up audiological evaluation demonstrated improved behavioral auditory responses and increased responsiveness to environmental sounds, as reported by the parents. CONCLUSIONS Cochlear implantation may provide meaningful auditory benefit in selected patients with Arnold-Chiari syndrome despite severe inner ear and central nervous system abnormalities. Comprehensive preoperative imaging and multidisciplinary assessment are essential for surgical planning and prognosis evaluation. Further studies involving larger patient cohorts are required to better define prognostic factors influencing cochlear implantation outcomes in this population.