[Incomplete partition type III revisited-long-term results following cochlear implant. German version]

Exploration of different electrode types inserted in a 3D model of a patient with incomplete partition type III inner ear malformation

BACKGROUND

Incomplete partition type III (IP III) represents a rare malformation of the inner ear, posing challenges during cochlear implantation due to inevitable cerebrospinal fluid (CSF) leaks and the potential misplacement of electrodes within the internal auditory canal (IAC). Despite the absence of a consensus on electrode selection, literature suggests both straight and perimodiolar electrodes as viable options for proper insertion. Limited implantation series contribute to the ambiguity in electrode choice. In this study, we evaluated the insertion performance of three electrode types in a 3D model simulating an IP III patient's inner ear.

METHODS

A 3D model replicating the inner ear of a patient with IP III undergoing surgery was created, incorporating a canal wall up mastoidectomy and an enlarged round window approach. Insertions were carried out using a straight electrode, a perimodiolar electrode, and a slim perimodiolar electrode, inserted through a sheath in the basal turn of the cochlea. Electrode positions were assessed after each insertion, with each type being tested 20 times.

RESULTS

Successful insertion rates were 95 % for the slim perimodiolar electrode, 85 % for the perimodiolar electrode, and 75 % for the slim straight electrode. Notably, the slim perimodiolar electrode required an adapted insertion technique due to the altered cochlear position in IP III cases. Statistical analysis revealed the slim perimodiolar electrode's superiority over the slim straight electrode in achieving successful insertions.

CONCLUSIONS

The 3D model of the IP III inner ear proved to be an effective tool for electrode testing and insertion training prior to surgery. Following multiple insertions in the 3D model, the slim perimodiolar electrode demonstrated the highest success rate, emphasizing its potential as the preferred choice for cochlear implantation in IP III cases.

X-linked Malformation Deafness: Neurodevelopmental Symptoms Are Common in Children With IP3 Malformation and Mutation in POU3F4

Supplemental Digital Content is available in the text.

Incomplete partition type 3 (IP3) malformation deafness is a rare hereditary cause of congenital or rapid progressive hearing loss. The children present with a severe to profound mixed hearing loss and temporal bone imaging show a typical inner ear malformation classified as IP3. Cochlear implantation is one option of hearing restoration in severe cases. Little is known about other specific difficulties these children might exhibit, for instance possible neurodevelopmental symptoms.

Embryology, Malformations, and Rare Diseases of the Cochlea

Despite the low overall prevalence of individual rare diseases, cochlear dysfunction leading to hearing loss represents a symptom in a large proportion. The aim of this work was to provide a clear overview of rare cochlear diseases, taking into account the embryonic development of the cochlea and the systematic presentation of the different disorders. Although rapid biotechnological and bioinformatic advances may facilitate the diagnosis of a rare disease, an interdisciplinary exchange is often required to raise the suspicion of a rare disease. It is important to recognize that the phenotype of rare inner ear diseases can vary greatly not only in non-syndromic but also in syndromic hearing disorders. Finally, it becomes clear that the phenotype of the individual rare diseases cannot be determined exclusively by classical genetics even in monogenetic disorders.