Cochlear Implantation in Arnold-Chiari Malformation Type 1: Expanding the Boundaries of Pediatric Neuro-Otology

Arnold-Chiari malformation (ACM) is a rare congenital hindbrain anomaly, with types 1-4 depending of degree of herniation of posterior fossa contents. The incidence of type 1 ACM is highest, with most cases being asymptomatic. Cases are incidentally picked up; however, some may present with headache, cough, paresthesia, and very rarely, symptoms of compression of lower cranial nerves such as sensorineural hearing loss. Surgical challenges are anticipated due to associated skeletal malformations and raised intracranial pressure. The youngest reported case-a 3-year-old girl with delayed speech and language milestones-is presented, in whom ACM type 1 was incidentally diagnosed. Audiological workup revealed profound sensorineural hearing loss in both ears. After multidisciplinary clearance, she underwent right-sided cochlear implantation. Intraoperative challenges faced were dilated emissary veins, an anteriorly placed sigmoid sinus, and a low-lying dura. However, a full electrode insertion was achieved and confirmed on neural response telemetry. The postoperative course was uneventful. Literature review suggests this to be the youngest reported case of cochlear implantation in ACM type 1. While hearing loss in this case may have been unrelated to ACM, nonetheless, successful cochlear implantation is feasible with meticulous preoperative planning and intraoperative vigilance. After a thorough anatomical assessment, multidisciplinary preoperative workup, intraoperative vigilance, and neuro-anesthetist backup, cochlear implantation can be safely performed in children with ACM type 1.