Cochleostomy management in patients with enlarged vestibular aqueduct receiving cochlear implants

Enlarged vestibular aqueduct (EVA) is the most common, radiographically evident abnormality of the inner ear in association with congenital or early onset sensorineural hearing loss. It can occur in isolation or in association with other inner ear malformations, such as the Mondini malformation. Cochlear implantation is an effective hearing rehabilitation option for patients with profound hearing loss, even in the presence of EVA and many other inner ear anomalies. However, congenital anomalies of the inner ear are associated with an increased incidence of both cerebrospinal fluid (CSF) leak at cochleostomy and aberrant facial nerve course, which can lead to postoperative CSF leak, meningitis, and facial nerve complications in association with cochlear implantation. In isolated EVA, a CSF leak is presumably caused by the dilated endolymphatic sac, which defectively allows communication with the subarachnoid space CSF in the posterior fossa. Additionally, occult osseous modiolar and interscalar septum deficiencies may exist and, thus, allow communication with the subarachnoid space CSF at the distal internal auditory canal. Therefore, modifications of the cochleostomy technique may be necessary in patients with EVA and other inner ear anomalies. We routinely use temporalis muscle to pack the cochleostomy site after electrode insertion. Additionally, oxidized nitrocellulose and temporalis muscle are used to pack the eustachian tube before cochleostomy to prevent CSF rhinorrhea in such patients.