Inner ear malformations – overview, current classifications, challenges in management

Introduction: Some patients with profound sensorineural hearing loss have inner ear malformations. Initially, those were believed to be a contradiction to cochlear implantation. However, with the advance of cochlear implant surgery and technology, it has become possible to treat this group of patients. However, cochlear implantation in the case of inner ear malformations can be associated with numerous surgical difficulties and possible complications. Purpose: The paper aims to present: (1) modern classification of inner ear malformations, (2) surgical and clinical challenges related to all types of malformations, and (3) cases of inner ear malformations identified in the authors’ centers. Material and methods: Of 111 children enrolled for cochlear implantation in three clinical centers, a group of patients with malformations of the inner ear was selected. We analyzed: preoperative imaging studies of patients performed prior to cochlear implantation, hearing tests, surgical protocols of cochlear implantation, results of intraoperative measurements and intraoperative imaging studies. We discuss what is currently believed to be the leading classification of inner ear malformations. Results: In 19/111 (17%) children, we diagnosed severe inner ear malformations in 35 ears. In 13/19 (68%) patients the malfor mations were bilateral and symmetrical, while 6/19 (32%) patients had different malformations in the right and left ear or one-sided malformation. All inner ear malformations described in the classification were found, except for rudimentary oto cyst. The most common are: cochlear hypoplasia, incomplete partition, and enlarged vestibular aqueduct. Discussion: Severe inner ear malformations are a major diagnostic and clinical challenge in children qualified for cochlear implantation. They can preclude or considerably complicate cochlear implantation and postoperative care. Inner ear malformations are found in imaging studies even in 20 to 30% of patients with profound hearing loss.