Observations on Mastoid versus Ear Canal Recorded Cochlear Microphonic in Newborns and Adults

Abstract

The cochlear microphonic (CM) may play an important role in the diagnosis of auditory neuropathy (AN) in newborns. However, since the CM tends to mirror the waveform of the acoustic stimulus, conscientious recording methodology must be applied to separate true response from artifact. The difficulty in achieving this separation has limited the clinical usefulness of the CM. In an effort to call attention to the importance of recording protocol when measuring the CM, the present study was designed to optimize CM recordings in humans by investigating the following parameters: (1) secondary minus electrode recording site (mastoid versus ear canal [EC]), (2) stimulus parameters, and (3) grounding and shielding conditions. Normative data were collected in full-term newborns (n = 7) and adults (n = 4) with no known risk factors for cochlear or retrocochlear pathology. Results suggest that the CM is easier to separate from stimulus artifact using an EC electrode and toneburst stimuli. In addition, electromagnetic shielding and grounding of the electrode cables and the acoustic transducer were effective in reducing and/or eliminating stimulus artifact. Results from this normative study may be helpful in improving the diagnostic utility of the CM in AN and other hearing-related disorders.

Using a Concha Electrode to Measure Response Patterns Based on the Amplitudes of Cochlear Microphonic Waveforms Across Acoustic Frequencies in Normal-Hearing Subjects

“…Thus, we focused on the response patterns, not on comparison with OAE measurements. This is consistent with other CM studies in this area, which also did not include OAE measurements (Dallos 1981;Kusakari et al 1988;Ponton et al 1992;Ferraro & Durrant 2002;Riazi & Ferraro 2008;Zhang 2010). This study has established a response pattern and has laid a foundation for new studies in the future.…”

“…As such, interest in the development of an approach using noninvasive narrowband CM measurements is increasing. Some research has already been done which may facilitate the development of the CM approach in the assessment of cochlear functions (Zhang & Abbas 1993;Riazi & Ferraro 2008;Zhang 2010).…”

Characteristics of cochlear microphonics in infants and young children with auditory neuropathy

“…However, so far, there is still no physiological method in clinical practice accepted as a specific approach with definite significance to differentiate sites-of-lesion in AN patients. In the last decade, investigation of CMs has been one of the foci of AN research [7][8][9][10][11][12][13][14][15], but the role of the CM I/O function curve in AN diagnosis was seldom reported. This paper introduces our research on CM evoked by clicks through the ABR test in infants and young children with AN.…”

Predicting Auditory Nerve Survival Using the Compound Action Potential

“…Several techniques for recording auditory evoked potentials have been developed to improve differential diagnosis of hearing disorders such as acoustic neuromas, auditory neuropathy, and Ménière's disease/endolymphatic hydrops (Don et al 2005;Ferraro & Durrant 2006;Riazi & Ferraro 2008) and to predict prognosis in cochlear implant recipients (Hall 1990;Gibson & Sanli 2007). Mills (2006) suggested that the combined use of auditory brain stem response (ABR) thresholds and distortion-product otoacoustic emission (DPOAE) amplitudes could differentiate between hearing loss related to stria vascularis damage and noise-induced hearing loss in an animal model.…”