The Efficacy of the Hearing Threshold Level at 3 kHz I/O Curve in DPOAE in Screening the High Risk Neonates in NICU / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Universal infant hearing screening has been recommended by the National Institutes of Health. Although the distortion-product otoacoustic emissions (DPOAE) hold promise as a screening technique, the validity oftheir input/output function curve (I/O curve) in the screening of neonates has not been fully investigated. The aims of this study were to determine the efficacy of the I/O curve as a hearing screening test and to investigate the prevalence of sensorineural hearing loss (SNHL)(moderate to severe degree) in high risk neonates. MATERIALS AND METHOD: A total of 69 ears of 35 infants at risk for hearing loss were tested with both DPOAE and auditory brainstem responses (BR). Auditory brainstem response results were used as the standard for hearing. The hearing threshold level at 3 kHz in I/O curve and the amplitude of distortion product in the DP audiogram were calculated and compared with the results of ABR. Neonates whose hearing thresholds were worse than 60 dB in the I/O curve were regarded as 'test-positive' and neonates whose hearing thresholds were worse than 60dB in ABR were regarded as 'disease-positive'. The sensitivity and the specificity of each test were calculated and the correlations between the response of each test and ABR threshold were also studied. RESULTS: The prevalence of SNHL in neonates in the SNUH neonatal intensive care unit was 5.79%. The sensitivity and specificity of the screening test using the I/O curve were 100% and 63.1%, respectively. The test using the DP amplitude for SNHL showed the sensitivity of 100% and the specificity of 18.46%. This was much lower than that of the screening test using the I/O curve. There was a positive correlation between the I/O threshold and ABR threshold (r=0.43), but there were no statistically significant correlations between the DP amplitude and the ABR threshold nor between the DP amplitude and the I/O threshold. CONCLUSIONS: The test using the I/O threshold in DPOAE is suitable for the screening of the SNHL in neonates with high sensitivity and relatively high specificity. Moreover, the I/O threshold could predict the audiometric threshold more correctly than the DP amplitude could.

Clinical Presentation and Management of Labyrinthine Fistula in Chronic Otitis Media with Cholesteatoma / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Labyrinthine fistula is a potentially serious complication of cholesteatoma. During or after surgery, cholesteatoma induced labyrinthine fistula can result in partial or total destruction of cochleovestibular functions.This study aimed to evaluate the efficacy of preoperative tests for predicting fistulas and postoperative hearing results according to surgical management. MATERIALS AND METHODS: A retrospective study of the clinical records of 1,712 patients who were operated for chronic otitis media with cholesteatoma from January 1979 through April 2001 in a tertiary university hospital in Seoul area. Of 1,712 patients studied, patients who were proved to have labyrinthine fistulas during operation for cholesteatoma were collected. The results of the pre- and postoperative bone conduction pure tone average and pure tone threshold at 4 kHz were analyzed in those patients. The fistula test,the temporal bone CT scan (TBCT) and intraoperative findings were also evaluated. RESULTS: Labyrinthine fistulas were found in 140 (8.2%) patients in this study. Fistulas were most commonly found in the lateral semicircular canal (91.7%) and fistulas in lateral semicircular canal were more accurately detected than the fistula of the other sites either by fistula test or by TBCT. Positive fistula test results and positive temporal bone CT findings in labyrinthine fistula cases were recorded in 36.3% and 74.1% of cases, respectively. Canal wall down mastoidectomy procedures were applied in 134 ears (95.7.%). The cholesteatoma matrix was removed in 129 ears (92.1%). The average bone conduction threshold showed no significant difference between pre- and postoperative evaluations overall. But in matrix-removed group, the change in the bone conduction level was significantly different between patients having fistula same or larger than 2 mm and smaller than 2 mm. CONCLUSIONS:The high resolution temporal bone CT scan is highly recommended for detection of labyrinthine fistulas. The postoperative hearing results are not affected by the type of mastoidectomy procedures but may be affected by the management of cholesteatoma matrix when the fistula is large in this study.

Effects of Phase Difference on the Latency of Compound Action Potential (CAP) in the Harmonic Stimulation / 대한이비인후과학회지

BACKGROUND AND OBJECTIVE: Comprehensive auditory evaluation often requires complex sounds in addition to pure tones. The sum of pure tones (harmonic stack) is a useful complex stimulus in examining auditory response interactions. In a harmonic stimulus, the phase relationship between pure tones may affect the results of auditory evaluation. The aim of this study was to investigate the effects of relative phases between harmonic frequencies on the latency of compound action potentials (CAP). MATERIALS AND METHODS: Relative phases between two frequencies of a harmonic were varied systematically and compound action potentials (CAP) were, then, recorded in guinea pigs in response to these stimuli. These latencies were compared with the latency to the harmonic complex with the relative phase of zero. RESULTS: The latency of the CAP was shifted within a restricted range to the stimuli with systematically varied phases. These relative phases between the two frequencies directly affected the temporal waveform of the harmonic stimulus although all of these stimuli exhibited the same frequency spectrum. Some phase spectra appeared to contribute more to the latency difference of the CAP. CONCLUSIONS: Findings indicated that the phase relationship in a tonal complex is important to the latency of the CAP, and the phase should be controlled carefully in the objective auditory evaluation with tonal complex stimuli.

Digitalized Stimulus Synthesis System for Audiological Evaluation / 대한이비인후과학회지

Background and Objective: Fast and reliable methods of synthesizing various auditory stimuli have been demanded both in clinical and in experimental auditory evaluations. Computerized digital stimulus synthesis system was developed to achieve the accuracy of stimulus waveforms, the simplicity of controlling stimulus parameters, and the flexibility of generating complex stimuli. MATERIALS AND METHODS: The system consisted of an AD / DA Board (GW Instrument), Macintosh computer system (Apple Computer Inc), and custom-made timing devices to digitally synthesize auditory stimuli. Developed programs controlled various parameters of this hardware system in real time. RESULTS: The system generated pure tones (default frequency range: 0.001-25000 Hz), harmonic stacks (components up to 10 tones), white noises (with various Gaussian variances). These synthesized stimuli were controlled by systematically varying presentation parameters such as rise / fall times, presentation duration, repetition rates, and phase relationship between frequencies. Conclusions: This stimulus synthesis tool was fast, exact, and versatile in generating and controlling stimuli for the audiological evaluation.

Clinical Analysis of Congenital Stapedial Fixation in Children / 대한이비인후과학회지

BACKGROUND: In congenital stapedial fixation, hearing could be restored by surgery on stapedial footplate. Stapes surgery was not a common operative method especially in children due to reported leakage of cerebrospinal fluid(perilymph gusher) and postoperative sensorineural hearing loss as well as low prevalence of stapedial fixation in Korea. OBJECTIVE: To evaluate the clinical manifestations and surgical results of congenital stapedial fixation. MATERIALS AND METHODS: From Dec. 1980 to Mar. 1996, authors experienced 17 cases of stapes surgery for congenital stapedial fixation in 14 children at Seoul National University Hospital. The clinical manifestations, preoperative and postoperative audiologic findings and complications were analyzed. In 10 ears, total stapedectomies were performed and partial stapedectomies were performed in other 3 ears. In the remaining 4 ears, stapedotomies were performed. RESULTS: Preoperative mean bone and air conduction thresholds were 15 dB, 62 dB respectively and mean air-bone gap was 47 dB. After stapes surgery, mean bone and air conduction thresholds were 12 dB, 32 dB respectively at the last audiologic follow-up. No perilymph gushers or significant sensorineural hearing loss were encountered. CONCLUSION: Stapes surgery is a safe and effective method in the management of congenital stapedial fixation.