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Study of cochlear microphonic potentials in auditory neuropathy

INTRODUCTION Auditory Neuropathy/Dyssynchrony is a disorder characterized by the presence of Otoacoustic Emissions and Cochlear Microphonic Potentials, an absence or severe alteration of Brainstem Evoked Auditory Potential, auditory thresholds incompatible with speech thresholds and altered acoustic reflexes. The study of the Cochlear Microphonic Potential appears to be the most important tool for an accurate diagnosis of this pathology. OBJECTIVE Determine the characteristics of the Cochlear Microphonic in Auditory Neuropathy/Dyssynchrony using an integrative review. METHODS Bibliographic survey of Pubmed and Bireme platforms and MedLine, LILACS and SciELO data banks, with standardized searches up to July 2014, using keywords. Criteria were established for the selection and assessment of the scientific studies surveyed, considering the following aspects: author, year/place, degree of recommendation/level of scientific evidence, objective, sample, age range, mean age, tests, results and conclusion. RESULTS Of the 1959 articles found, 1914 were excluded for the title, 20 for the abstract, 9 for the text of the article, 2 for being repeated and 14 were selected for the study. CONCLUSION The presence of the Cochlear Microphonic is a determining finding in the differential diagnosis of Auditory Neuropathy/Dyssynchrony. The protocol for the determination of Cochlear Microphonic must include the use of insert earphones, reverse polarity and blocking the stimulus tube to eliminate electrical artifact interference. The amplitude of the Cochlear Microphonic in Auditory Neuropathy/Dyssynchrony shows no significant difference from that of normal individuals. The duration of the Cochlear Microphonic is longer in individuals with Auditory Neuropathy/Dyssynchrony.

Suppression of Otoacoustic Emissions Evoked by White Noise and Speech Stimuli

Introduction: Suppressing otoacoustic emissions is one of the objectives, noninvasive methods that can be used to assess the efferent auditory system. When the ascending reticular activating system is stimulated, the cortex becomes more alert. The system reacts better to an important stimulus than an unimportant one. Objective: Assess the effect of suppressing otoacoustic emissions by transitory stimulus in the presence of different auditory stimuli in normal listeners. Methods: This cross‐sectional, observational analytical study. The sample was composed of eight participants. The following procedures were adopted: recording otoacoustic emissions, suppression with white noise, suppression with white noise and pure tone, auditory training, new recording of suppression with white noise and pure tone, suppres‐ sion using a speech pattern, suppression using a reversed speech pattern, suppression using familiar speech, and suppression using reversed familiar speech and suppression singing “happy birthday” in a familiar voice. Results: There was a significant difference between the otoacoustic emission values, mainly at frequencies of 1000 and 1500 Hz. Conclusion: Individuals submitted to the effects of suppression exhibit more effective results at frequencies of 1000 and 1500 Hz. Furthermore, it was found that the efferent activity of the auditory system is more efficient when it involves the use of the speech spectrum.