Abnormal positive potentials in round window electrocochleography

Objective: To describe an atypical waveform, termed an abnormal positive po tential (APP), on round window electrocochleograms (RW ECochG) of children and to relate its occurrence to clinical history. Study Design: APPs were identified prospectively, and a retrospective analy sis was made of these patients' clinical histories, audiograms, and auditor y outcomes (hearing aid, cochlear implant, or nonauditory communication) Setting: Tertiary referral teaching hospital, day surgery and clinics. Patients: All 431 children <110 months of age suspected of a severe to prof ound hearing loss who underwent RW ECochG From January 1993 to August 1997. Intervention: Diagnostic RW ECochG for auditory threshold estimation. Main Outcome Measure: The presence on the RW ECochG of the APP: an early po sitive potential in the absence of a compound action potential (CAP). Results: An APP was observed in 34 children. The APP was most marked in res ponse to clicks and 8-kHz tones. The APP click threshold averaged 70 dB hea ring loss. The brainstem evoked potential of these children showed an absen ce of waves, or a broad positive wave with no subsequent waves. Twenty-nine of 30 behavioral audiograms obtained were indicative of severe to profound hearing loss. Auditory outcomes were available from 26 children; 45% of th em derived no help from a hearing aid, and 8 children received a cochlear i mplant. Clinical factors frequently associated with APP were prematurity in combination with kernicterus or hypoxia. Conclusions: APP thresholds were lower than neural thresholds or behavioral thresholds. Children with APP need close follow-up, because half of those studied needed nonauditory strategies to develop effective communication.