Auditory brainstem response. Sensory assessment by bone conduction masking

Auditory brainstem response (ABR) thresholds to clicks were determined for 15 normal hearing adults and for four patients with conductive, sensorineural, or mixed hearing losses. Conductive losses were created in five of the normal hearing adult subjects for which threshold assessment was repeated. The response to a click at 5 dB above threshold was masked with a high-pass, bone-conducted noise. For both the patients and the normal subjects, subtracting 15 dB from the amount of noise required to mask this ABR response approximated sensory threshold. Tympanometry was performed on all patients, except one exhibiting unilateral congenital atresia, to confirm middle ear status.

Auditory brainstem responses in children with otitis media with effusion

Auditory brainstem responses (ABR) were recorded in 14 infants and toddlers and 12 school-age children with a previous history of recurrent otitis media with effusion (OME), or otoscopic and tympanometric evidence of persistent OME, or both. ABR tests were performed immediately before and after myringotomy and tympanostomy tube insertion in the younger subjects. For the school-age children, ABR tests were performed following otoscopy, tympanometry, and pure tone audiometry. The results demonstrate that the latency of both wave I and wave V of the ABR was sensitive (82% and 100%, respectively) to the presence of OME. Wave I also identified the absence of OME (specificity = 100%) whereas wave V did not (specificity = 25%). ABR latency was significantly decreased postoperatively in ears found to have OME, but not in ears found to have no OME. In the school-age subjects the ABR was used to predict the conductive hearing loss at 4000 Hz with less than a 20 dB error in virtually all subjects. The ABR latency delay was also found to be related to conductive hearing impairment at lower pure tone frequencies and to the average conductive loss at a variety of pure tone frequencies. Predictions of the presence of a conductive hearing loss from these relationships promise to be impressively accurate. The results suggest that the ABR can be a valuable tool for detecting the presence of conductive hearing impairment in infants and young children suspected to have OME and perhaps as an estimate of the degree of impairment.

An evaluation of speech audiometry by bone conduction in hearing-impaired adults

Pure-tone thresholds, speech reception thresholds (SRT), and speech discrimination scores (DS) were obtained by ac and bc on 20 normal-hearing and 30 hearing-impaired adults. Correlations between the SRT and pure-tone thresholds (ave. of .5, 1, and 2 kc/s) were significant by both ac and bc. Correlations between DS by ac and bc were also highly significant, indicating the value of the bc DS in specific difficult cases. The clinical observation was confirmed statistically of decreasing DS with increasing sensorineural hearing loss.

Hemifacial microsomia: priorities and sequence of comprehensive otologic management

Hemifacial microsomia is evidenced by the clinical spectrum of microtia, mandibular deformities, and middle ear malformations. This constellation of defects suggests that the most efficacious treatment will be multidisciplinary management, which includes the otolaryngologist, audiologist, plastic surgeon, and temporal bone radiologist. In the past, microtia--the most clinically apparent malformation--usually has been studied and treated with respect to the area of special interest of the investigator, whether from an otologic, reconstructive, or radiologic perspective. Newer management, however, utilizes the combined skills of the clinical and behavioral disciplines in the treatment of the microtic auricle, associated middle ear pathology, and hearing loss. Such multidisciplined approach, commencing during the first year of life, is deemed advisable to cope with the severe unilateral or bilateral hearing loss which may lead to potentially serious sensory deprivation and impede adequate language development in these children.

[Brain stem potentials evoked by "click" (author's transl)]

The authors describe the results of click at a recurrence frequency of 10 C/S in evoked responses of the brain stem, firstly in twenty normal individuals, with headphones or in a free area, making it possible to define a range of physiological responses to the different intensities, then in seventeen pathological individuals consisting of six cases of conduction deafness and eleven of perceptive deafness. On the basis of this study, they attempt to demonstrate the value of this type of examination not only in the determination of objective auditory threshold, but also in that of the type of deafness: conductive or perceptive. The method even makes it possible to approximately define the general appearance of the frequency distribution at the threshold according to the slope of the different latencies of P5. In the opinion of the authors, the chief advantages are the decrease in the time required for the test and the possibility of its use in the study of prosthetic gain.

[Causes of inner ear deafness; a critique of therapy (author's transl)]

In spite of recent criticisms, the diagnosis of inner ear hearing impairment is based on both pure tone thresholds and suprathreshold tests. The acoustico-facial reflex is useful only when used in conjunction with the suprathreshold tests.--Noise-induced deafness is generally confined to the higher frequencies of sound, and only exceptionally involve the middle frequencies as well. Low-tone hearing impairment may represent a partial symptom of Meniere's Disease as well as functional hearing loss. Zoster oticus produces a sensory hearing impairment but not a neural one, as might be expected from the neurotropy of the Herpes virus. Patients with socalled presbyacusis exhibit criteria of inner ear pathology which may represent a summation of different noxious agents damaging the inner ear throughout life rather than result from the physiologic process of aging. Traumatic hearing impairment seldom progresses, and usually involves central parts of the auditory pathways following blunt trauma.--We believe that uncritical therapy with vasodilating drugs is not useful in sensory hearing loss, especially if it is continued for months and if several drugs are employed at the same time. The danger of an unintended decrease in blood pressure is greater in these patients since many also suffer from hypotension which can then cause vascular insufficiency to the inner ear, similar to the "steal" effect. Therapy for inner ear hearing loss remains the responsibility of the otolaryngologist, and should still be based on proper diagnosis.

Cholesteatoma with intact tympanic membrane: a report of 41 cases

Aural cholesteatoma may present itself as an unexplained hearing impairment without either perforation or otorrhea and without radiologic evidence of bone destruction. The etiology is probably congenital. In our cholesteatoma cases, 3.7% occur in individuals with an intact tympanic membrane. Most of these patients have had the disease 5 years or less and 50% are under 20 years of age. Complications of the disease are uncommon in this group. All but 1 of our 41 cases were managed with the intact canal wall technique. Most were reexplored (planned second-stage) and residual disease was encountered in 32%. One should keep the possibility of a congentital cholesteatoma in mind wheneger encountering a unilateral serous otitis media or an unexplained unilateral conductive hearing impairment, regardless of the patient's age.

Vascular anomalies of the middle ear

The patient presenting with a red mass behind the eardrum and a pulsating tinnitus may well have a vascular tumor. One must be ever mindful, however, that the mass may represent a congential vascular anomaly. The most common one seen is the uncovered jugular bulb in which the vessel extends superiorly into the middle ear to or above the incudostapedial joint. More rare is the uncovered and posteriorly displaced carotid artery. The purpose of this paper is to review the literature on the subject of vascular anomalies of the middle ear and temporal bone and to discuss the diagnosis and management of these lesions. Illustrative case reports with color photographs are presented as well.

Application of brain stem response in brain-injured children

The early components of the auditory evoked potential within 10 msec following an auditory stimulus are attributed to the brain stem auditory nuclei and pathways. In pediatric neurology the auditory brain stem response (ABR) can be applied to: 1) differential diagnosis of hearing impairment in young children including objective threshold measurement of hearing, 2) electrophysiological evaluation of maturation of the auditory pathways, 3) diagnosis of the site and/or extent of neurlogical diseases affecting the brain stem and 4) observation of a degenerating process of degenerative diseases in the central nervous system. The paper is especially concerned with the application of ABR to severe neurological diseases in children including central auditory dysfunction, cerebral palsy, infantile spasm, adrenoleucodystrophy, anoxic brain damage and Down's syndrome. Value and limitation of ABR audiometry in the clinical practice were mentioned, and a special emphasis was placed on the fact that all types of auditory tests including behavioral, electrophysiological, and developmental tests are indispensable, because the ABR, like other indicators, also has its own limitation.

Clinical accuracy of tuning fork tests

A review of the literature reveals a surprisingly sparse amount of true documentation concerning the validity of using tuning forks as an adjunctive measure in the diagnosis of hearing impairment. Most reports are historical or anecdotal. With this in mind, a protocol was set up to identify the value of three standard tuning fork tests--the Rinne, the Weber, the Bing Occlusion--at frequencies of 256, 512 and 1024 Hz. The data were compared to otologic examination, audiometry and acoustic impedance. Results indicate the Rinne, Weber and Bing Occlusion tests do not accurately predict the type of hearing impairment as frequently as the literature suggests.

Auditory brain stem evoked responses to bone-conducted signals

Auditory brain stem evoked responses to air-conducted and bone-conducted signals were recorded in subjects with normal hearing and in subjects with conductive hearing loss. In normal subjects, the latency to wave V for bone-conducted signals was approximately 0.5 ms longer than the latency for air-conducted signals delivered at the same sensation level. In conductive hearing loss, the separation of the latency-intensity functions for air conduction and bone conduction (corrected for the 0.5-ms delay) provided a valid estimate of the behavioral air-bone gap in the 1,000- to 4,000-Hz region.

The Wildervanck syndrome: cervico-oculo-acoustic dysplasia

The Wildervanck syndrome consists of the Klippel-Feil deformity of the spine, eyeball retraction, lateral gaze weakness, and hearing loss. Conductive hearing loss, as well as a more frequently occurring sensorineural hearing loss, is caused by dysplasia of the inner ear. Typically, polytomograms demonstrate a bulbous vestibule and dilated lateral semicircular canals with basilar impression of the skull. The Duane's eyeball retraction phenomenon completes the syndrome; this may be explained either by misdirected innervation of the extraocular muscles or by atrophy or fibrosis of the lateral rectus muscles.

Influence of otitis media on hearing and development

Otitis media affects nearly every child at some time; many children have mild-to-moderate hearing losses for prolonged periods. The effects of these losses on language and educational development may be significant; possible mechanisms are discussed. Especially in suboptimal listening situations, speech perception may be impaired by even a mild hearing loss. Patterns of imperception are predicted by comparison of composite audiometric data from children with middle ear effusions with speech power data, and by analysis of sound pressure waveforms of speech filtered to simulate the typical hearing loss of these patients. A new method of analysis of brain stem evoked responses, yielding response components attributable to binaural interaction, is reported. This and other evoked response techniques may be able to identify objective changes in auditory nervous system function attributable to relative sensory deprivation during development. Finally, directions for further research in this area are discussed.

Occupational hearing loss. The significance of asymmetrical hearing thresholds

In 1873 consecutive patients referred for compensation assessment for presumed industrial hearing loss, 281 (15%) had an average difference in hearing threshold between the ears of 15 dB at 1/2, 1, 2 and 4 kHz. An unrelated cause was found in 115 (6%). It was due to trauma in 37 (2%), unexplained in 32 (1.7%) and attributed to noise exposure in 97 (5.2%). The possible mechanisms for noise as a cause are discussed and include shielding of one ear from noise, unequal recovery after severe noise exposure, and unequal sensitivity of the ears. After extensive investigation, including X-rays, vestibular tests and some myelograms, no treatable disorder was discovered.

The correlation between negative middle ear pressure and the corresponding conductive hearing loss in children. A 12-month study of 352 unselected 7-year-old children

An epidemiological study of negative middle ear pressure in children made it possible to test its relationship to conductive hearing loss. About 350 children were subjected to a screening procedure recording audiogram and middle ear pressure five times during a 12-month period. Those children who failed to perceive just one tone or who had a middle ear pressure equal to or worse than -150 mmH2O in one or both ears were referred to the Hearing Clinic for conventional audiometry and middle ear pressure measurement each month. By computing the weighted average of the regressions for each child, a straight linear relationship was found between negative pressure and conductive hearing loss. In addition, a frequency dependence was found, the hearing loss being maximal at about 500 Hz. In general, the study shows that tympanometry is of limited value in predicting hearing loss in a child. The threshold for pathology of about -150 mmH2O, being a predisposing factor in secretory otitis media, corresponds to the upper confidence limit of the normal range of hearing loss found in this series. There is no distinct value of negative pressure that clearly distinguishes between normal and pathological condition, but it is concluded that a middle ear pressure worse than -150 mmH2O should be considered a probable hearing handicap.

Diagnostic delay in deafness - the effect of active case finding

Impaired hearing, sensorineural or conductive, was detected in 464 (25 per cent) of the 1,876 children tested during visits with a mobile hearing clinic in rural northern Ontario. Seven severe to profoundly deaf preschool children were identified; expected prevalence in this population is 5--10 preschoolers. Three older children (7--15 years of age), also, were found to have severe to profound deafness that previously had been undetected. Previously, initial identification of severe sensorineural hearing loss in this age group in these areas was at an average age of 30 months. Since visits by the clinic this is 18 months. Conductive hearing losses that had inhibited learning were identified earlier than the reported average (6.4 years vs 5.3--9.0 years of age). Follow-up has shown more effective management of conductive hearing loss since visits by the clinic. Few rural Ontario communities with populations under 10,000 have adequate surveillance for hearing problems. The goal of The Hospital for Sick Children's Mobile Hearing Clinic is to identify early all children with hearing problems and to speed the introduction of a better program for the recommendation and fitting of hearing aids, including proper counselling in the use of amplification.