Electrically Evoked Auditory Brain Stem Responses for Lateral and Medial Placement of the Clarion HiFocus Electrode

• Published in: Ear and hearing Vol. 24; no. 2; pp. 184 - 190
• Main Authors: Firszt, Jill B, Wackym, Phillip A, Gaggl, Wolfgang, Burg, Linda S, Reeder, Ruth M
• Format: Journal Article
• Language: English
• Published: Baltimore, MD Lippincott Williams & Wilkins, Inc 01-04-2003; Lippincott Williams & Wilkins
• Subjects: Adult; Aged; Aged, 80 and over; Auditory Threshold - physiology; Biological and medical sciences; Ear, auditive nerve, cochleovestibular tract, facial nerve: diseases, semeiology; Electric Stimulation - instrumentation; Electrodes, Implanted; Evoked Potentials, Auditory, Brain Stem - physiology; Female; Head and neck surgery. Maxillofacial surgery. Dental surgery. Orthodontics; Humans; Male; Medical sciences; Middle Aged; Non tumoral diseases; Otorhinolaryngology. Stomatology; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Surgery of the ear, the auditive nerve and the facial nerve; Human; Positioning; Brain stem; Internal ear disease; Auditory disorder; Electrodes; Electrodiagnosis; Treatment; Auditory evoked potential; Cochlear implant; ENT disease; Perception hearing loss; Sensory hearing loss
• ISSN: 0196-0202; 1538-4667
• DOI: 10.1097/01.AUD.0000061230.58992.9A

OBJECTIVEThe purpose of this study was to compare the electrically evoked auditory brain stem response (EABR) for lateral and medial placement of the Clarion HiFocus cochlear implant electrode array via the electrode positioning system (EPS).
DESIGNTwenty-five adult and pediatric cochlear implant recipients participated in the study. Intraoperatively recorded EABRs were evoked by stimuli via three intracochlear electrodes representing apical, medial, and basal locations, and responses were elicited before and after positioner insertion. Evoked potential measures of wave V amplitude and threshold were examined for statistical significance using ANOVA for repeated measures and Chi-Square methods.
RESULTSFor a given supra-threshold stimulus level, the increase in EABR wave V amplitude was significantly larger after EPS placement compared to before EPS placement for electrodes 1 (apical) and 13 (basal). Likewise, when the stimulus was decreased to obtain a minimal amplitude, the wave V threshold was significantly lower after EPS placement for electrodes 7 (medial) and 13. The number of measurements that showed decreased wave V threshold after EPS insertion was significantly dependent on intracochlear electrode location.
CONCLUSIONSPlacement of the Clarion Electrode Positioning System following HiFocus electrode insertion resulted in a reduction in the electrical current required to activate the auditory system. The effect of the EPS was greatest for the basal location, demonstrated by lower wave V thresholds and a larger percentage increase in wave V amplitude. The EABR reflected electrophysiologic changes relative to lateral-to-medial changes in intracochlear electrode position due to the EPS.