Bilateral Cochlear Implantation in Four Children / 대한이비인후과학회지

The benefits of bilateral cochlear implants (CIs) include better understanding of speech in noise and localization of sound sources. Following the improvement observed in adults, children were also included in the bilateral CIs program. The aim of this study was to investigate the impact of bilateral CIs use on speech perception in quiet and in noise. Four children underwent testing from 9 to 18 months after activation of bilateral hearing. Speech perception tests in quiet and in noise (signal to noise ratio of +10 dB) were performed in all children with the first CI alone and bilaterally. Subjects showed varying degrees of improved performance on speech perception tests in quiet and in noise according to bilateral auditory experience. Bilateral CIs can offer a substantial benefit in speech perception in quiet and in noise. The extent of the advantage, however, may require a more prolonged period of adjustment and learning.

Vestibular Evoked Myogenic Potentials Produced by Stimulation with 500 Hz-tone Burst / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Vestibular evoked myogenic potential (VEMP) is muscle reflex caused by surface electrodes following repeated high-intensity auditory stimulation. The current study attempted to determine whether VEMP can be consistently evoked from the sternocleidomastoid muscle (SCM) by the 100 dB air-conducted and 50 dB bone-conducted 500 Hz-tone burst. SUBJECTS AND METHOD: Air-conducted and bone-conducted VEMPs in response to 500 Hz-tone burst were recorded from the SCM of 13 normal volunteers. Subjects were seated on their chairs and made to hold their heads turned up as far as possible towards the side, contralateral to the stimulated ear voluntarily. Two different sound durations (rise/fall time=2 msec, plateau time=2 msec[2/2] and rise/fall time=5 msec, plateau time=5 msec[5/5]) were presented through a insertphone or bone vibrators. Latencies and amplitudes of p13 and n23 responses were measured. RESULTS: All normal volunteers showed p13-n23 responses to 50 dB bone-conducted tone burst as well as to 100 dB air-conducted tone burst. The values of latency of p13 and n23 were the most reliable at 5/5 air-conducted in evaluation by coefficiency of variance. Mean p13 and N23 latencies by airconducted tone burst were significantly longer than those of bone-conducted. Mean p13-n23 amplitudes by air-conducted tone burst were significantly larger than those by bone-conducted at 2/2 sound duration. CONCLUSION: VEMP could be consis-tently evoked by the 100 dB air-conducted and 50 dB bone-conducted 500 Hz-tone burst, especially at 5/5 air-conducted.

Comparison of Auditory Brainstem Response and Auditory Steady-State Response Thresholds in Infants and Young Children / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The aim of this study was to assess the accuracy of threshold estimates determined by the auditory steady-state response (ASSR) in a group of sedated infants and young children with a range of hearing losses. MATERIALS AND METHOD: Two studies were performed because the behavioral audiometric information was not available from infants and young children. In the first study, a retrospective analysis was performed for 36 children (mean age: 3 years 4 months) who had completed auditory brainstem response (ABR) and pure tone audiometry to verify that ABR threshold is a good predictor for pure tone threshold in our laboratory. The ABR thresholds to 500 Hz, 1000 Hz tone-pip and click were compared with behavioral thresholds. In the second study, a prospective analysis of 23 children (mean age: 12 months), the ABR thresholds to 500 Hz, 1000 Hz tone-pip and click were compared with ASSR thresholds to amplitude and frequency modulated tones. RESULTS: The first study in which strong correlations were found between ABR and pure tone thresholds (r> or =0.92) demonstrated that ABR thresholds could be used to predict the pure tone thresholds. The second study which showed that ASSR thresholds were highly correlated with ABR thresholds (r> or =0.93) indicated that ASSR thresholds provided reliable audiometric information in infants and young children. CONCLUSION: These studies showed that ASSR could be used to estimate hearing thresholds with reliable accuracy in infants and young children.

Auditory Neuropathy: A Report of Three Cases / 대한이비인후과학회지

Auditory neuropathy is a hearing disorder characterized by an absent or severely abnormal auditory brainstem response, with preservation of the cochlear microphonics and otoacoustic emissions. This suggests that outer hair cell (OHC) function is normal but that auditory function proximal to the OHCs is impaired. These patients demonstrate mild to severe hearing loss for pure tones and impaired word discrimination out of proportion to pure tone loss. Hearing aid alone is of little or no benefit in patients with auditory neuropathy. Visual support via cued speech or signed language can be a fail-safe method for insuring language development. Recently, there are some reports that cochlear implantation is highly successful in patients with auditory neuropathy. We report three cases (two children and one woman) with auditory neuropathy. Each patient was tested with cochlear microphonics, otoacoustic emissions, auditory brainstem response and middle latency response, etc. All three patients had normal cochlear microphonics or otoacoustic emissions with absent auditory brainstem response. Two of them had evidence of a peripheral neuropathy. We should be aware of auditory neuropathy and implications for its management, which differs from treatment of sensorineural hearing loss. Auditory neuropathy also raises a concern about the risk of false-negative findings when newborn hearing screening is restricted to otoacoustic emissions.