Effect of congenital inner ear malformations (IEMs) on electrically evoked compound action potential (ECAP) responses in cochlear implant children

PurposeThe study was designed to assess the electrically evoked compound action potential (ECAP) responses in children with inner ear malformations compared to children with normal inner ear anatomy.MethodsThe study included 235 prelingual deaf children who were implanted in cochlear implant unit in King Fahad University hospital-Imam Abdulrahman Bin Faisel University. Subjects were using either Cochlear Nucleus or Medel cochlear implant devices. We had 171 (64.5%) subjects with normal inner ear anatomy and 94 (35.5%) subjects with inner ear malformations (IEMs) and they were classified into 6 groups according to inner ear anatomy. Fourteen subjects (14.9%) subjects had enlarged vestibular aqueduct (EVA), 30 (32%) subjects had Mondini deformity, 25 (26.6%) subjects had incomplete partition type two (IPII), 9 (9.6%) subjects had incomplete partition type one (IPI) and 16 (17%) subjects had hypoplastic cochlea type III or IV. Intraoperative electrically evoked compound action potential (ECAP) responses were analyzed and compared in all subjects.Results and conclusionsMeasurable ECAP responses can be elicited in patients with IEMs in most of the channels. Severe malformations can affect the prevalence of measuring ECAP and getting identifiable waveform morphology. Additionally, increased thresholds and lower slope of AGF was observed in IEMs specially in more severe malformations (e.g. IPI). IPI patients with better word recognition scores tended to show more identifiable ECAP measurements. This could suggest the presence of some correlation between ECAP responses and patients' performance after cochlear implantation.

Automated summary

The study aimed to assess the ECAP responses in children with inner ear malformations compared to children with normal inner ear anatomy. It was found that measurable ECAP responses can be elicited in most channels in patients with IEMs. However, severe malformations can affect the measurement of ECAP and the identification of waveform morphology. Additionally, patients with more severe malformations tend to have higher thresholds and lower slope of AGF. IPI patients with better word recognition scores tend to show more identifiable ECAP measurements, suggesting a possible correlation between ECAP responses and patients' performance after cochlear implantation.