Incomplete partition type III revisited-long-term results following cochlear implant

Area of Science:

• Otolaryngology
• Neurosurgery
• Audiology

Background:

• Incomplete Partition type III (IP III) is a malformation characterized by a missing lamina cribrosa between the cochlea and internal auditory canal (IAC).
• Cochlear implantation (CI) in IP III patients carries a risk of electrode array insertion into the IAC.
• Evaluating surgical protocols and outcomes in IP III patients is essential for improving CI efficacy.

Purpose of the Study:

• To assess CI surgery protocols, long-term audiological outcomes, and electrophysiological data in patients with IP III.
• To analyze mapping data, stapedius reflexes, electrode impedances, and ECAP thresholds in IP III patients post-CI.
• To compare speech discrimination scores in IP III patients with a control group with normal cochlear morphology.

Main Methods:

• Eight IP III patients who underwent cochlear implantation with perimodiolar electrode arrays were retrospectively analyzed.
• Mapping data, stapedius reflexes, electrode impedances, and ECAP thresholds were evaluated.
• Speech discrimination was assessed using standardized tests and compared to a matched control group.

Main Results:

• A significant increase in pulse width, electric load, and basal electrode impedances was observed in IP III patients 3 years post-CI.
• Intraoperative electrically-evoked stapedius reflexes were successfully measured in all IP III patients.
• Speech recognition scores in IP III patients were lower than in controls, though not statistically significant.

Conclusions:

• The observed increase in electrode impedances over time in IP III patients may be attributed to fibrosis and cochlear nerve neurodegeneration.
• Long-term audiological results following CI in IP III patients are generally stable.
• Intraoperative imaging and stapedius reflexes are recommended to ensure correct electrode array placement in IP III cases.