Incomplete Partition Type 3 (IP-III) is a rare congenital cochlear malformation and is associated with X-linked deafness radiologically characterized by the absence of the modiolus, absence of cribriform plate and an enlarged internal auditory canal (IAC) with preserved interscalar septa. Preoperative recognition of this anomaly is essential, as cochlear implantation (CI) is challenging due to the high risk of perilymphatic gusher. We present the case of a 4-year-old male with delayed speech development and bilateral severe-to-profound sensorineural hearing loss (SNHL). Otoacoustic emission (OAE) and BERA reported severe to profound bilateral hearing loss with probable cochlear origin. High-resolution computed tomography (HRCT) of the temporal bone revealed a cochlea with corkscrew appearance, absence of the modiolus, and an enlarged IAC, consistent with IP-III. Magnetic Resonance Imaging (MRI) showed a normal cochlear nerve with no additional labyrinthine malformations. These findings confirmed the diagnosis of IP-III, guiding preoperative evaluation for cochlear implantation, given the potential surgical risks. This case highlights the critical role of HRCT and MRI in diagnosing IP-III, a rare but clinically significant cochlear anomaly. Recognizing its distinct radiological features is essential for differentiating it from other incomplete partition anomalies (IP-I, IP-II) and for anticipating intraoperative complications during cochlear implantation.
Keywords: Cochlear implant; HRCT temporal bone; Hearing loss; Incomplete partition; Inner ear; Malformation.
© 2026 The Author(s).