DOI: https://doi.org/10.36347/sasjs.2026.v12i05.034

Pages: 529-533

Background: Cochlear nerve hypoplasia (CNH) is a congenital anomaly characterized by underdevelopment or absence of the cochlear nerve and represents an important cause of congenital profound sensorineural hearing loss. Cochlear implantation (CI) in patients with CNH remains controversial due to the reduced number of functional nerve fibers, which may limit electrical signal transmission and result in variable auditory outcomes. Accurate preoperative evaluation of both anatomical and functional integrity of the auditory pathway is therefore essential, and a multimodal approach is required, as no single test can reliably predict cochlear implant benefit. Materials and Methods: We report two pediatric cases of bilateral prelingual profound deafness who underwent comprehensive preoperative assessment. Evaluation included behavioral audiometry, auditory brainstem response (ABR) testing, high-resolution computed tomography (CT) of the temporal bone, and magnetic resonance imaging (MRI) with parasagittal views of the internal auditory canal to assess cochlear nerve morphology. Functional assessment consisted of intraoperative promontory stimulation, electrically evoked auditory brainstem responses (EABR), and cochlear implant telemetry with impedance measurements and electrically evoked compound action potentials (ECAPs). Cochlear implantation was performed using a perimodiolar electrode array. Results: Both patients demonstrated bilateral profound sensorineural hearing loss with absent ABR wave V responses at maximal stimulation. Imaging revealed severe cochlear nerve hypoplasia or aplasia associated with inner ear malformations, including internal auditory canal stenosis and vestibular abnormalities, while cochlear morphology was preserved. Despite these findings, promontory testing elicited reproducible low-amplitude responses at high stimulation thresholds, indicating residual neural excitability. Intraoperative EABRs confirmed the presence of electrically evoked resp