Intra-Operative Electrophysiological Monitoring: Comparing the CR220 Hand-Held Device Versus Standard Clinical Software

Background:
Technology for electrophysiology monitoring on a cochlear implant intra-operatively is gaining prominence. Typical measurements involve measuring impedance and Evoked Compound Action Potential (ECAP) to determine the implant integrity and confirm functional neural-electrical interface. This study evaluates the performance of standard clinical software versus a simple hand-held intra-operative measurement device.

Method:
Intra-operative electrophysiological measurements were conducted using the Nucleus hand-held CR220 remote assistant intra-operative measurement unit, and standard Custom Sound EP (CSEP) v4.4 software. Impedance and ECAP measurements were collected for all 22 channels using both CR220 and CSEP respectively. The results were compared with respect to ECAP threshold differences and number of measurable electrodes.

Results:
68 sets of intra-operative measurements were collected from adult and pediatric subjects with and without unusual aetiology during a 6 month period. Total number of measured electrodes on CR220 and CSEP is 1302. Average absolute ECAP threshold difference between CR220 and CSEP is 5.50 CL with SD=6.67 including outliers. ECAP thresholds from CR220 and CSEP had a correlation coefficient of 0.91. There is a high correlation between unusual aetiology and number of non-measurable electrodes in ECAP measurement, however, age and hearing loss history of the patient did not show significant correlations.

Conclusions:
Unusual aetiology was more likely to cause measurement difficulties with both CR220 and CSEP, therefore, more thorough electrophysiological testing such as Electrical Auditory Brainstem Response (EABR) is recommended. Patients with normal aetiology and medical history generally have complete ECAP responses. ECAP responses collected from CR220 and CSEP did not show significant differences.