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Published on: October 8, 2014
Abnormal positive potentials in round window electrocochleography
S J O'Leary1, T E Mitchell, W P Gibson
1Department of Otolaryngology, Royal Victorian Eye and Ear Hospital, Melbourne, Australia.
Insights
An abnormal positive potential (APP) on round window electrocochleograms (RW ECochG) in children may indicate severe hearing loss. Half of affected children required non-auditory communication strategies for development.
Area of Science:
- Pediatric audiology
- Neurophysiology
- Otolaryngology
Background:
- Severe to profound hearing loss in children presents diagnostic challenges.
- Round window electrocochleography (RW ECochG) is a tool for auditory threshold estimation.
- Atypical waveforms may offer further diagnostic insights.
Purpose of the Study:
- To describe an abnormal positive potential (APP) waveform on RW ECochG in children.
- To correlate the occurrence of APP with clinical history and auditory outcomes.
Main Methods:
- Prospective identification and retrospective analysis of clinical data for children undergoing RW ECochG.
- Analysis included audiograms, auditory outcomes, and clinical history.
- Focus on children under 110 months with suspected severe to profound hearing loss.
Main Results:
- APP was observed in 34 children, most pronounced with clicks and 8-kHz tones.
- APP click thresholds averaged 70 dB HL; brainstem evoked potentials showed abnormalities.
- Clinical factors like prematurity, kernicterus, or hypoxia were frequently associated with APP.
Conclusions:
- APP thresholds were lower than neural or behavioral thresholds.
- Children with APP require close follow-up due to a high likelihood of needing non-auditory communication strategies.
Objective:
To describe an atypical waveform, termed an abnormal positive potential (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 analysis was made of these patients' clinical histories, audiograms, and auditory 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 profound 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 positive potential in the absence of a compound action potential (CAP).
Results:
An APP was observed in 34 children. The APP was most marked in response to clicks and 8-kHz tones. The APP click threshold averaged 70 dB hearing loss. The brainstem evoked potential of these children showed an absence 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 them derived no help from a hearing aid, and 8 children received a cochlear implant. Clinical factors frequently associated with APP were prematurity in combination with kemicterus 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.
