Fluctuating and/or progressive sensorineural hearing loss in children.

Sensorineural hearing loss (SNHL) which is sudden in onset, fluctuating, and/or progressive complicates medical management, hearing aid selection, and individualized educational planning for a hearing-impaired child. In spite of multidisciplinary evaluation and intervention, a gradual decrease in auditory acuity may continue unabated in a significant number of cases. Intercurrent middle ear disease and inconsistent audiologic technique can account for threshold variation in some cases. The study population consisted of 229 children (132 boys; 97 girls) aged 1 to 19.9 years at first audiogram which revealed at least a mild degree of sensorineural hearing loss in one or both ears (35 unilateral), and who demonstrated threshold variation of 10 dB or more in at least one ear at one or more of the standard audiometric test frequencies (250, 500, 1000, 2000, 4000, and 8000 Hz) and were without concurrent middle ear disease (mean length of follow-up, 4.9 years; mean number of audiograms, 10.3). Of 365 ears demonstrating threshold variation of 10 dB or more, 22 (6%) had purely progressive losses without intercurrent upward fluctuation, 208 (57%) had fluctuating thresholds with gradually progressive losses, and 135 (37%) had intermittent threshold fluctuation without permanent deterioration. The probability of contralateral threshold fluctuation if one ear fluctuated was 0.91, while the probability of contralateral progressive SNHL if one ear progressed was 0.67. Demographic data, presumptive etiology, degree of initial SNHL, audiometric configuration, and symmetry of threshold variation were considered as potential predictors of the likelihood of threshold fluctuation and/or progression.

Physiologic chest sounds and helicopter engine noise.

To develop an amplification system for physiologic chest sounds during air medical transport in jet helicopters, we compared frequency spectra of physiologic chest sounds and Allison C-28 equipped jet helicopter noise. We found that the frequency spectrum of physiologic chest sounds is contained entirely within that of jet rotocraft noise. Attempts to amplify physiologic chest sounds or to filter jet rotorcraft noise will invariably fail to improve perception of chest sounds. Future research must focus on assessment of actual movement of the chest and of each hemithorax, as well as an carbon dioxide production, as indicators of adequate ventilation and proper endotracheal tube position.

Middle ear disease in young children with sensorineural hearing loss.

Early identification of children with sensorineural hearing loss (SNHL), coupled with the provision of appropriate conventional amplification constitute important elements of a (re)habilitative strategy. Often overlooked, however, is the problem posed by recurrent and chronic middle ear disease in the child with coexisting SNHL. This study focuses on 437 (237 boys and 200 girls) consecutive patients with bilateral SNHL, in the moderate range or poorer, who were diagnosed prior to age 5 years at Boys Town National Research Hospital. The mean threshold shift with effusion was 25.0 dB at 250 Hz, 28.5 dB at 500 Hz, 29.5 dB at 1000 Hz, 24.5 dB at 2000 Hz, and 27.5 dB at 4000 Hz. During a median follow-up period of 3.21 years, 154 (35.2%) of these children required surgical placement of tympanostomy tubes because of the severity of middle ear disease and its impact on auditory acuity. Accurate determination of the degree and audiologic configuration of a SNHL may be seriously hindered by a coexisting middle ear effusion. If initial findings indicate the presence of a middle ear effusion, measures of auditory function must be repeated after the effusion has been resolved by medical and/or surgical intervention.

Noise-induced hearing loss in children.

Occupational noise exposure remains the most commonly identified cause of noise-induced hearing loss (NIHL), but potentially hazardous noise can be encountered during leisure-time activities. NIHL in the pediatric population has received scant attention. This study focuses on 114 children and adolescents (ages 19 and under: 90.3% males) who were diagnosed as having probable NIHL on the basis of history and audiometric configuration. In 42 children the loss was unilateral, while the remaining 72 had sensorineural losses of varying configurations in the contralateral ear. The mean age of referral for evaluation was 12.7 years (range 1.2 to 19.8, SD 4.21), although 26% of these losses were diagnosed in children aged 10 years and younger. Such irreversible, but potentially preventable losses, should be given high priority on the public health agenda. Comprehensive, age-appropriate educational programs must be developed for elementary and secondary students and their parents to acquaint them with potentially hazardous noise sources in their environment.

Unilateral hearing loss in children.

Recent reports suggest that early onset, severe unilateral sensorineural hearing loss (USNHL) in children may be associated with significant deficits in auditory and psycholinguistic skills and school performance. This report reviews a consecutive series of 324 children and adolescents (202 males, 122 females) with documented USNHL evaluated at the Boys Town National Research Hospital. The left ear was affected in 168 (52%) and the right ear in 156 (48%). Based on speech frequency threshold averages (i.e., 500, 1000, and 2000 Hz), the losses were classified by severity as follows: borderline, 43 (13%); mild, 51 (16%); moderate, 40 (12%); severe, 19 (6%); profound, 31 (10%), and anacusic, 50 (15%). The remaining 90 children (28%) had high frequency losses (i.e., above 2000 Hz). The mean and median age of diagnosis were 8.78 years and 7.75 years. Temporal bone imaging studies, auditory brainstem responses (ABRs), and vestibular evaluations were performed on selected cases. Etiology was uncertain in 34.8% of cases, while hereditary factors (12.6%), head trauma (10.8%), and perinatal risk factors (10.7%) were the most commonly identified etiologies. Thirty-one percent of the children had scholastic or behavioral problems in school. A concerted effort aimed at early identification and intervention in cases of USNHL is warranted.

Severe versus profound sensorineural hearing loss in children: implications for cochlear implantation.

The advent of cochlear implants for children has stimulated interest in the specific sensory deficits and communicative capabilities of children with severe or profound bilateral sensorineural hearing loss. Appropriate management of these children and their families requires an appreciation of the multifaceted developmental and educational challenges confronting deaf children, even after cochlear implantation. Evaluation results from 200 children with bilateral sensorineural deafness (63 severe/137 profound, anacusic, and fragmentary) reveal significant differences between these two subpopulations. Within the profoundly impaired group, important differences were also noted in the children's ability to benefit from conventional amplification, depending on residual hearing at or above 1000 Hz. Strategies for assessing auditory function and aided benefit in severely and profoundly hearing-impaired children must involve a pediatric test battery, serial evaluations, and parental cooperation/support. When selecting candidates for cochlear implantation, it is inappropriate to categorize severely hearing-impaired children with those children having profound sensorineural losses. Even profoundly impaired populations are not homogeneous, and rehabilitation potential with conventional amplification must be determined on an individual basis, over time.

Auditory brainstem responses from graduates of an intensive care nursery: normal patterns of response.

Auditory brainstem responses (ABR) were obtained from graduates of an intensive care nursery (ICN) when those babies were in stable physiological states and ready for hospital discharge. Intensity ranged from ABR threshold to 80 dB nHL, and all recordings were made in a sound-isolated chamber. The data reviewed here are from 585 babies having presumably normal hearing, based upon bilateral ABR thresholds of 30 dB nHL or less. To insure that estimates of population statistics were not biased by high correlations between ears, only the data from the left ears were used in most analyses. Larger correlations were observed between conceptional age (CA) and ABR latencies than between either gestational age (GA) or chronological age (CHA) and the same latencies. Data were grouped into six CA groups for further analyses. Distributions of all response-component latencies were similar in shape and depended upon CA, showing orderly decreases in latency with increasing age. None of these distributions differed significantly from normal, and they were well fitted by normal ogives. Thus, accurate estimates of percentiles can be obtained from the means and standard deviations. The results indicate that it is important to take CA into account when evaluating ABR latencies.

The effects of tocainide on audiological and electrophysiological responses in humans.

This study reports on the systematic audiological evaluation of 18 cardiac patients receiving tocainide, an orally administered cardiac antiarrhythmic agent. The results of an audiological site of lesion test battery were compared with auditory brain stem response (ABR) measures. Of 35 ears tested, 17 (48%) presented ABR findings consistent with retrocochlear pathology. Audiological signs of retrocochlear pathology occurred less frequently and often in patients in whom ABR results suggested normal hearing or cochlear hearing loss. These data demonstrate that an extraneous agent, in this case tocainide, can affect ABR transmission times and that it is important to recognize such possible effects in order to interpret ABR data appropriately.

Cerebrospinal fluid parameters and auditory brainstem responses following meningitis.

Auditory brainstem responses were measured in 94 children under 24 months of age immediately following treatment for bacterial meningitis. Evidence of peripheral hearing loss (thresholds of 30 dB HLn or greater) was found in 47% of the patients. In addition, 9% had prolonged interwave latencies, indicating the possible presence of retrocochlear pathology. Other clinical data were examined as well. CSF glucose concentration correlated with both the presence and magnitude of hearing loss (as measured by auditory brainstem responses). Magnitude of hearing loss also was associated with the presence of seizures. Although all children recovering from meningitis should be assessed for hearing loss, those who have had low CSF glucose concentrations and seizures appear to be at high risk.

Some comparisons between auditory brain stem response thresholds, latencies, and the pure-tone audiogram.

Aspects of auditory brain stem responses (ABR) and pure-tone behavioral audiograms were compared in patients with cochlear hearing loss. Click-evoked ABR thresholds appeared to be related most closely to the audiometric thresholds at 2000 and 4000 Hz, with relatively poor agreement at either 1000 or 8000 Hz. These results were related to the amplitude spectrum of the eliciting stimulus. The slope of the wave V latency-intensity function appeared to be related to the configuration of the hearing loss. Patients with high-frequency sensorineural losses had steeper slopes than normal subjects, whereas patients with flat sensorineural losses had shallower slopes. These results were related to the principle that response latency is determined by the cochlear region that predominates the ABR for different stimulus intensities.

The effects of stimulus duration on ABR and behavioral thresholds.

ABR and behavioral thresholds were estimated as a function of stimulus duration for three normal and two hearing-impaired subjects. Stimuli were 2000-Hz tone bursts with 0.5-ms rise/fall times and durations ranging from 1 to 256 or 512 ms. For both groups of subjects, ABR thresholds were independent of stimulus duration. Normal subjects showed greater improvement in behavioral thresholds as a function of duration than did subjects with hearing losses. Thus, it appeared that ABR and behavioral thresholds were affected differently by changes in stimulus duration and that the magnitude of these differences could depend upon the presence of hearing loss. These data indicate that temporal integration may be one factor which makes comparisons between ABR and behavioral thresholds complicated. In the present study, the magnitude of hearing loss, measured by the ABR, would have been underestimated if normal behavioral thresholds for short-duration stimuli were used as the reference.

Quantifiable hearing and no ABR: paradox or error?

Reports concerning the inability to record at least wave V of the ABR in patients with quantifiable hearing have generally been confined to patients with demonstrable neurological diseases. Four patients with no neurological evidence of brainstem dysfunction in whom the ABR's were either absent or showed thresholds inappropriate for the audiometric configurations are presented.

Cochlear distortion: effect of direct-current polarization.

Intermodulation components (combination tones) appearing in microphonic potentials were measured from guinea pig cochleas with and without polarizing direct currents passing through the cochlear partition. At moderate intensities of stimulus the polarization had a qualitatively different effect on the distortion components than on their eliciting primaries or on pure tones simulating the distortion products. At high intensities, the primaries and the combination tones were similarly influenced by the polarizing current. It is concluded that cochlear distortion is a two-stage process, mechano-electrical at low levels and mechano-hydraulic at high levels.