Hearing outcomes of cochlear implantation in IP-II (Mondini dysplasia) – A systematic review

OBJECTIVES: Incomplete Partition type II (IP-II), or Mondini dysplasia, accounts for half of congenital cochlear malformations and results in profound sensorineural hearing loss. Cochlear implantation restores hearing in patients with IP-II however low numbers mean reporting of auditory performance outcomes is limited. Here we review English language articles between 2010 and 2025 reporting hearing outcomes following cochlear implantation in individuals IP-II. RESULTS: Categories of Auditory Performance (CAP), Speech Intelligibility Rating (SIR) and parental reports of cochlear implantation in 731 individuals, across 20 studies, with a follow-up of 1-3 years, met the inclusion criteria. Findings suggest that auditory perception and speech develop more slowly in people with IP-II compared to controls but there was no difference between groups by 1-2 years post-implantation. DISCUSSION: Most patients with IP-II have better hearing with a cochlear implant than before. However, there is limited evidence that this is comparable to those with normal middle ear anatomy. Findings were typically derived from questionnaires with small cohorts and short follow-up. CONCLUSION: Patient counselling for people IP-II should identify that prediction of hearing outcomes is uncertain. Informed prognostication of timing of surgery and hearing outcomes after cochlear implantation in IP-II needs further study with long-term follow-up including surgical and hearing outcome measures.