Effect of anesthetic gas on middle ear fluid.

Tympanometry was performed before (preoperative) and after (intraoperative) the administration of inhalation anesthesia including nitrous oxide and halothane on 109 children undergoing myringotomy with pressure equalization tube insertion. A total of 213 preoperative tympanograms were compared with their intraoperative counterparts and the presence or absence of middle ear effusion at myringotomy. When preoperative tympanograms were consistent with pneumatized middle ears, intraoperative findings demonstrated a mean middle ear pressure increase of +147 daPa. When preoperative tympanometry suggested middle ear effusion, less than 1% demonstrated intraoperative tympanometric changes and/or findings at surgery that would support anesthesia clearing middle ear effusion. Preoperative tympanometric data were poor predictors of the presence or absence of effusion at myringotomy. The relationship between inhalation anesthetics (i.e., nitrous oxide and halothane) and middle ear fluids, and the reliability of tympanometry to predict middle ear effusion are discussed.

Central auditory imperception.

The development of clinically applicable techniques for the evaluation of hearing impairment caused by lesions of the central auditory pathways has increased clinical interest in the anatomy and physiology of these pathways. A conceptualization of present understanding of the anatomy and physiology of the central auditory pathways is presented. Clinical tests based on reduction of redundancy of the speech message, degradation of speech and binaural interations are presented. Specifically performance-intensity functions, filtered speech tests, competing message tests and time-compressed speech tests are presented with the emphasis on our experience with time-compressed speech tests. With proper use of these tests not only can central auditory impairments by detected, but brain stem lesions can be distinguished from cortical lesions.

Acoustical factors of noise created by suctioning middle ear fluid.

OBJECTIVE: To quantify the intensity, spectral content, and duration of exposure for suction noise created during aspiration of middle ear fluid following myringotomy. DESIGN: Case series. SETTING: Tertiary care center. PATIENTS OR OTHER PARTICIPANTS: Convenience sample of 245 myringotomies performed on 124 patients ranging in age from 6 months to 14 years (mean age, 2 years 8 months). MAIN OUTCOME MEASURES: Intensity, spectral content, and duration of exposure associated with suction noise were defined by electroacoustic analysis of high-fidelity tape recordings of the noise created during suctioning middle ear fluid. RESULTS: The intensity of suction noise ranged from 74 to 117 dB; most acoustic energy was concentrated in the frequency range between 1.7 and 6.0 kHz, and the duration of exposure varied from 4 to 23 seconds.

Measures of middle ear admittance during experimentally induced changes in middle ear volume in the hamster.

The relation between middle ear admittance measured at the tympanic membrane and middle ear volume was studied in adult hamsters. A modified tympanometric procedure was used to measure complex admittance at eight test frequencies. Middle ear volume was varied by injecting small amounts of water into the bulla cavity. As bulla volume decreased, the value of admittance magnitude also decreased. The measured values of admittance magnitude could be accurately predicted by the equation for admittance magnitude until the bulla was about 70% filled. The results confirm that measures of middle ear admittance reflect the volume of the middle ear cavity as would be expected of a pure compliance. Where such measures are available in man, they might be used to predict the degree of fluid intrusion into the middle ear cavity.

ABR screening of high-risk infants: effects of ambient noise in the neonatal nursery.

This investigation examined ABR waveforms obtained at five signal intensities (20, 30, 40, 60, and 80 dB nHL) for adults and at three signal intensities (20, 40, and 80 dB nHL) for infants. ABR recordings were obtained in a quiet condition and repeated for three different intensity levels (40, 50, and 60 dBA) of background noise characteristic of a neonatal intensive care unit. The subjects were ten adults and ten infants whose ABRs were judged normal when measured at 20 dB nHL in the quiet condition. Results indicated that high levels of ambient noise (up to 60 dBA) did not influence either absolute wave V or interwave latencies measured for stimulus intensities of 60 and 80 dB nHL. ABR waveforms obtained at stimulus intensities often used for screening (i.e., 20, 30 or 40 dB nHL), however, were substantially altered for some subjects as a function of increasing levels of ambient noise. This observation was most apparent for the infant population and has important implications for the design of infant ABR screening programs.

Cholesteatoma in the pediatric patient.

A review of patients with cholesteatoma at the Children's Hospital of Philadelphia from 1981 to 1986 yielded 161 children. Analysis of data from both outpatient and hospital charts revealed a higher incidence of males to females, and the peak incidence of cholesteatoma appeared to be in the 6-10 year age group. Otorrhea was the most common symptom; and on physical examination, the posterior-superior quadrant was most often affected. Both intact canal wall and open cavity procedures were employed depending upon the site and extent of disease. Seventy-six percent of patients underwent an intact canal wall or middle ear procedure initially, with the remainder requiring an open cavity procedure. Recurrent or residual cholesteatoma was found in 32% of 148 patients at the second procedure, and in 7% of 148 patients if a third procedure was necessary. Pre- and post-operative audiometric findings for 91 patients revealed 21% with decreased hearing post-surgically, 50% with no change in hearing and 29% with improved hearing. Post-operative complications were minimal.

Delayed-onset hearing loss in respiratory distress syndrome: case reports.

The pre-, peri-, and postnatal histories for two infants who suffered respiratory distress syndrome (RDS) are presented. Each infant was diagnosed with RDS within 24 hours after birth, placed on high-frequency jet ventilation, and passed auditory brainstem response (ABR) screening prior to hospital discharge. Both infants were enrolled in a neonatal follow-up program with no report of hearing loss during the first year of life. At 2.5 years of age, each infant was found to have severe-to-profound sensorineural hearing loss. Neither infant suffered kidney failure, rubella, cytomegalovirus, or genetic involvement. Audiologic monitoring after hospital discharge was not performed because each infant passed the ABR screen. Thus, the date of onset and/or progression of hearing loss are unknown. Until additional research findings are available, we recommend that the hearing of any infant diagnosed with RDS be monitored frequently until 3 years of age.

Articulation index and hearing handicap.

This investigation examined the relationship between perceived hearing handicap and the Articulation Index (AI) and the extent to which this relationship was influenced by the variables age, gender, degree of hearing loss, and audiometric slope. Subject age, gender, pure-tone thresholds, and scores for the Self-Assessment of Communication (SAC) and the Significant Other Assessment of Communication (SOAC) were extracted retrospectively from 373 patient files (194 males, 179 females). Correlation analysis revealed a significant (p < .01) negative relationship between AI values and both measures of hearing handicap, and also indicated that SAC/SOAC total scores correlated significantly (p < .01) with each other. Partial correlation analyses revealed that degree of hearing loss was the only variable under study that had substantial influence on the strength of AI/hearing handicap correlations.

The effect of recreational gunfire noise on hearing in workers exposed to occupational noise.

Hearing sensitivity for an experimental group of 278 industrial workers who engaged in recreational shooting was compared with that of an age-matched control group of 278 nonshooting industrial workers to examine the effect of gunfire exposure on auditory thresholds. The influence of age and the number of unprotected gunshot exposures per year also was examined. The subjects in the experimental group completed a questionnaire to define the types of firearms used, the number of years shooting, and the number of protected and unprotected gunshot exposures per year. Results revealed that hearing sensitivity for frequencies 3.0, 4.0, and 6.0 kHz for both ears in the experimental group was an average of approximately 5 to 10 dB poorer than that of the control subjects. Although both subject groups demonstrated poorer 3.0-to-6.0-kHz hearing sensitivity for left-ear compared with right-ear listening, the degree of asymmetry between ears was greater for the experimental subjects. Older shooters had more hearing loss and greater threshold asymmetry than younger shooters, but there was no significant relationship between hearing sensitivity and the number of unprotected exposures per year. This latter finding was attributed to a fourfold increase in the number of unprotected annual exposures that were reported by younger shooters, who had inherently better hearing than did the older shooters.

Comparison of total harmonic distortion measures among hearing aid test systems.

Different types of hearing aid test equipment use different methods to calculate total harmonic distortion (THD). Comparisons of the THD measured by four commercially available systems were made by evaluating eight hearing aids, three times each. The results obtained were significantly different (p less than 0.001) among three of the test instruments. Furthermore approximately 10% of the hearing aids, which met the ANSI S3.22-1976 specifications for THD when tested with an apparatus that measures true THD, failed this measurement when evaluated on the other three systems.

Intelligibility of time-altered speech in relation to chronological aging.

The Northwestern University Auditory Test Number 6 (NU-6) measure of speech discrimination was time compressed and presented to four age groups ranging from 54 to 84 years of age. Experimental stimuli were presented at sensation levels of 24, 32, and 40 dB to an equal number of right and left ears and male and female subjects. Results indicated that intelligibility decreased as a function of increasing time compression and age and decreasing sensation level. Changes in speech intelligibility associated with the aging process appear to be closely allied to changes in the temporal resolving power of the central auditory processing system.

The development of middle-ear admittance in the hamster.

A high-frequency admittance meter was developed and used to study the maturation of physiological function in the middle ear of neonatal golden hamsters (Mesocricetus auratus). The middle-ear input admittance in the frequency range of 0.8-1.8 kHz was measured in animals ranging in age from 6 to 69 days postpartum. Admittance magnitude was found to increase steadily with age, beginning on day 16, to asymptotic values at each test frequency. There were no obvious differences in admittance growth rates within the range of frequencies tested. However, an analysis of the slopes of the admittance ma;nitude frequency response curves revealed an increase from 4.6 dB/octave for animals 25 days old or younger, to 6.3 dB/octave for all older animals. This difference between younger and older subjects indicates that the development of the middle ear in the golden hamster is more complex than a simple increase in pure compliance.

Middle ear immittance in rheumatoid arthritis.

Audiologic and electroacoustic immittance measurements were obtained from each ear of 23 patients with rheumatoid arthritis and 13 normal control subjects. Audiologic findings revealed 14 patients with rheumatoid arthritis with hearing loss of either conductive (three patients) or sensorineural (11 patients) type, while only two control subjects demonstrated hearing loss, both of sensorineural type. Immittance data revealed abnormal findings in 59% of the patients with rheumatoid arthritis as compared to only 4% of the control subjects. The increased incidence of sensorineural hearing loss in the sample with rheumatoid arthritis could not be readily explained. The observed prevalence of abnormal immittance findings in patients with rheumatoid arthritis suggested either increased middle ear stiffness or increased stiffness associated with decreased stability of ligamentous anchorage.

Meningitis and hearing loss in children.

The hospital records for 100 cases of meningitis in which acute audiometric data has been obtained were reviewed. The incidence of sensorineural hearing loss was found to be 6%. The severity of hearing impairment varied from mild to profound and was frequently bilateral and irreversible. Two-cases showed asymmetrical involvement, and in one case, there was subsequent improvement in threshold sensitivity. Factors that influenced the incidence of neurologic sequela included severity of the initial disease process, age of the patient, and duration of symptoms before diagnosis and treatment. We discuss the pathophysiologic mechanisms that may account for such hearing loss, and we emphasize the importance of early diagnosis and intensive antimicrobial therapy. Careful neurologic evaluation is required after recovery and must include periodic sequential audiometric testing.

Vision and hearing during deferoxamine therapy.

To determine the frequency of eye and auditory complications and their relationship to drug dosage and iron stores in patients receiving deferoxamine, we studied 52 regularly transfused patients who received deferoxamine by subcutaneous or intravenous infusion in doses from 26 to 136 mg/kg/day, and whose serum ferritin levels of 185 to 17,775 micrograms/L reflected a wide range of iron stores. Forty-nine patients (94%) had no evidence of drug-induced visual or auditory abnormalities. Symptomatic loss of vision and hearing developed in one patient; both problems improved when chelation therapy was stopped. Of the 51 symptom-free patients, one had a mild degree of macular stippling and one had a mild, bilateral, high-frequency sensorineural hearing loss. Eye and ear abnormalities in the symptom-free patients did not progress despite continuation or resumption of chelation therapy at the same dosage. Patients with ophthalmologic and audiologic abnormalities did not receive higher doses of deferoxamine and did not have lower serum ferritin levels than patients without such abnormalities. These findings demonstrate that eye and ear abnormalities during chelation therapy with deferoxamine may not occur uniformly at as high a frequency as previously reported, even in patients who receive large doses of the chelating agent or who have only modest amounts of excessive iron.