The Compound Action Potential in Subjects Receiving a Cochlear Implant

Area of Science:

• Neuroscience
• Audiology
• Biomedical Engineering

Background:

• The total response (TR) in cochlear implant (CI) patients accounts for 40-50% of speech perception variance.
• TR comprises both hair cell and neural components.
• Adding the compound action potential (CAP), a neural-only response, may improve TR's predictive power.

Purpose of the Study:

• To investigate if the CAP can improve the prediction of speech perception outcomes in CI subjects.
• To determine the correlation between CAP measurements and speech perception scores.

Main Methods:

• Intraoperative electrocochleography (ECochG) was performed on 238 adult and pediatric CI subjects.
• CAP was measured via amplitude and a fitted scaling factor.
• Results were correlated with consonant-nucleus-consonant (CNC) word scores at 6 months post-implantation.

Main Results:

• A measurable CAP was present in only about half of the subjects.
• CNC scores showed weak correlations with both CAP amplitude (r=0.20) and scaling factor (r=0.25).
• TR alone accounted for 43% of speech perception variance; CAP addition did not improve this.

Conclusions:

• Cochlear implant pathology frequently renders the CAP absent or highly variable.
• The TR is a more robust predictor of speech perception outcomes in CI patients than the CAP.