Evoked acoustic emissions from the human ear. VI. Findings in cochlear hearing impairment.

Click-evoked otoacoustic emissions (CEOAE) were recorded in 28 subjects with mild to moderate flat or steeply sloping cochlear hearing loss. We used the same equipment and recording technique as previously employed in the testing of newborns. A rescaling and subtraction procedure was implemented in an attempt to eliminate the tail of the stimulus artifact. However, in some cases the method also seems to eliminate a true response. In ears with flat losses and with identified CEOAE, no one had a hearing loss exceeding 40 dB HL in the mid-frequency region (0.5, 1 and 2 kHz). Conversely, in ears with flat losses and without CEOAE, no one had a hearing loss less than 30 dB HL in this frequency region. In ears with sloping hearing losses the thresholds at 1 and 2 kHz were most important for the generation of the CEOAE and a significant correlation between the emission amplitude at 70aud (approximately dB p.e. SPL) and the threshold at 1 kHz was found.

On the evidence of auditory evoked magnetic fields as an objective measure of tinnitus.

The purpose of the present study was to determine the utility of auditory evoked magnetic fields as an objective measure of tinnitus. The auditory evoked magnetic fields of 14 patients with tinnitus and of 14 sex- and age-matched controls were measured by means of a 7-channel BTI neuromagnetometer. Stimuli were 1 kHz tone-bursts presented randomly. Tinnitus patients and controls were similar with respect to latencies and amplitudes of the N100m and P200m, and with respect to the locations and moments of the equivalent current dipoles. The present study could not support the notion that specific abnormalities of the auditory evoked magnetic fields are characteristic of patients with tinnitus.

Otologic sequelae after pneumococcal meningitis: a survey of 164 consecutive cases with a follow-up of 94 survivors.

As part of a comprehensive study on sequelae after pneumococcal meningitis, 94 of 111 consecutive survivors were re-examined 4 to 16 years after discharge. Twenty-three patients had otological sequelae after pneumococcal meningitis. In these patients, 17 had hearing losses, 7 had tinnitus, 9 had vertigo, 13 had vestibular areflexia, 4 had loss of smell, and 3 had loss of taste. Among the patients with hearing loss, 4 were bilaterally deaf, 6 were unilaterally deaf, and 2 had mild and 5 had slight hearing losses. From correlations with extensive data from the medical records, preadmission antibiotic treatment appeared to protect from acousticovestibular damage. Purulent otitis media and otosurgical intervention did not correlate to the fatality rate or the development of sequelae. Acute purulent otitis media appeared as a concomitant manifestation, rather than the focus of pneumococcal meningitis.

Bilateral sudden deafness and acute acquired toxoplasmosis.

An 18-year-old woman, while suffering from acute acquired toxoplasmosis, experienced sudden deafness and a total loss of vestibular function first in the right ear and three months later also in the left. Following treatment with sulphadiazine and pyrimethamine, hearing was retrieved to such a degree that the patient was enabled to communicate by means of a body-worn hearing aid and lip-reading. Taking the differential diagnostic possibilities into account, we believe that toxoplasmosis was the cause of the severe hearing loss. Since effective treatment seems to be available, we recommend that patients with acute bilateral sensorineural hearing loss of unknown origin are examined for acute toxoplasmosis with a view to instituting chemotherapy.

Placebo effect in surgery for Menière's disease: nine-year follow-up.

A 9-year follow-up report of our study on endolymphatic shunt procedure versus mastoidectomy is presented. Success has been maintained in about 70% of the patients in both groups and no significant differences between the two groups have been found.

Otospongiosis and sodium fluoride. A clinical double-blind, placebo-controlled study on sodium fluoride treatment in otospongiosis.

The effect of sodium fluoride treatment in patients with otospongiosis has been evaluated in a prospective clinical double-blind, placebo-controlled study of 95 patients. The results showed a statistically significant greater deterioration of hearing loss in the placebo group than in the group actively treated with 40 mg of sodium fluoride daily. These results support the view that sodium fluoride can change otospongiotic, active lesions to more dense, inactive otosclerotic lesions.

Evoked acoustic emissions from the human ear. V. Developmental changes.

Twenty young children, in whom evoked acoustic emissions were recorded at birth, were re-examined at the age of 4 years. None of the children showed evidence of sensorineural hearing impairment and it was possible to record a reproducible emission in all ears, which displayed normal otoscopy and tympanometry (n = 9). The new recordings were compared with those obtained at birth and the latency and the amplitude of the response both appeared unchanged. However, in some ears the frequency content of the dominant part of the emission was considerably lower at the age of four. The implication of this finding is briefly discussed in view of recent data on cochlear development, obtained from animal research.

Evoked acoustic emissions from the human ear. IV. Final results in 100 neonates.

Evoked acoustic emissions were recorded from both ears in a series of 100 consecutive normal newborns. We used the same stimulus, a 2-kHz click, and recording technique as previously described. Analysis of the data showed that evoked emissions could be identified in all ears, except one at 70 dBaud (i.e. approximately 30 dB nHL). No significant differences could be demonstrated between males and females or between left and right ears with regard to the latency of the emissions, the peak-to-peak amplitude, the main frequency component, or the waveform correlation between the two 70 dBaud recordings in each ear. However, a significant correlation between left and right ears was found for the amplitude and frequency of the emissions. Practical and methodological problems related to the recording were elucidated. The tail of the stimulus artifact sometimes interfered with the first part of the emissions even though the recordings were made in a time window delayed 5 ms relative to the stimulus onset. We tried to solve this artifact problem by different off-line techniques, but found no useful solution. We therefore continued to use only a cosine tapering of the first 2 ms of the time window. Three different ways of determining latencies were evaluated and we found that the 'envelope' technique was the most simple and reliable. Recording of evoked acoustic emissions is a quick and non-invasive method and provided that the presence of the emissions is related to normal cochlear function, it can be used as a screening test in newborns.(ABSTRACT TRUNCATED AT 250 WORDS)

Endolymphatic sac-mastoid shunt surgery. A nonspecific treatment modality?

The reason for the effectiveness of endolymphatic sac-mastoid shunt surgery in the treatment of patients with Meniere's disease is still open for debate. In a double-blind study, published in 1981, we could not demonstrate any difference between the effect of a simple mastoidectomy and a regular endolymphatic sac-mastoid Silastic sheet shunt. However, a significant reduction in symptoms could be demonstrated in both groups, and 70% of patients in both groups could be classified as successes. The patients were reexamined 3 years after surgery, and it was still not possible to demonstrate any differences between the sham and the active surgery. In this study, no significant differences between the two groups have been found at follow-up averaging 84 months, and success has been maintained in about 70% of patients. The only three failures, who have consistent vertiginous attacks, have been confined to the actual shunt group. Two patients in the active group have lost their hearing as compared with none in the sham group, and 35% of the patients have now developed bilateral disease. We believe that endolymphatic sac-mastoid shunt surgery is a nonspecific treatment modality, and we find no need for sac shunt surgery. The vast majority of the patients can be successfully treated by nonsurgical means, but we emphasize that above all the patient must be assured that in the event of persistent debilitating symptoms, a surgical solution to the problem is available.

Otospongiosis and sodium fluoride. A blind experimental and clinical evaluation of the effect of sodium fluoride treatment in patients with otospongiosis.

The effect of sodium fluoride treatment in patients with otospongiosis has been evaluated blindly in a morphological and microchemical element analysis of otospongiotic specimens together with a prospective clinical double-blind, placebo-controlled study. The results show that using the calcium/phosphorus ratio as an indication for bone maturity, the sodium fluoride treatment can stabilize otospongiotic lesions in retaining calcium relative to phosphorus. The clinical double-blind, placebo-controlled study of 95 patients showed a statistically significant worse deterioration of the hearing loss in the placebo group than in the active treated (40 mg sodium fluoride daily) group, supporting the view that sodium fluoride can change otospongiotic, active lesions to more dense, inactive otosclerotic lesions. We have postulated in the past that the actual mechanism of the cochlear loss is toxic enzymes produced by histiocytes at the periphery of the microfoci, and it may be that sodium fluoride has some effect on these enzymes.

Evoked acoustic emission: clinical application.

Stimulated acoustic emissions were recorded in response to tonal stimuli at 60 dB p.e. SPL in a small group of normal-hearing adults. Power spectral analysis reveals that the evoked activity from each ear contains energy in preferential frequency bands and the change of stimulus frequency has only a minor effect on the power spectra, i.e. the maximum jumps from one spectral peak to another. Experiments with deconvolution demonstrate that the emission generating system at least at a fixed intensity can be regarded as being linear and characterized by its impulse response which is similar to the emission evoked by click stimuli. It is concluded that significant information is obtained by the click rather than by the tonal stimuli. The click-evoked emissions were also recorded from both ears in a consecutive series of 100 full-term and otherwise normal babies 2-4 days after birth. The emission amplitudes were of the same order of magnitude as those previously found in normal-hearing adults. Cross-correlation analysis was performed in order to evaluate reproducibility and the combination of amplitudes and correlation coefficients from supra-threshold recordings and the no-stimulus recordings reveals presence of a true emission from all ears tested. It is concluded that the cochlear echo can be recorded in normal-hearing newborns with an extremely low rate of type I errors.

Placebo effect in surgery for Meniere's disease: a three-year follow-up study of patients in a double blind placebo controlled study on endolymphatic sac shunt surgery.

In a previously published double blind, placebo controlled study, the efficacy of an endolymphatic sac-mastoid shunt was compared with a purely placebo operation (mastoidectomy) in controlling the symptoms in 30 patients with typical Meniere's disease. Minor differences could be demonstrated after one year between patients with the shunt versus the sham operation, but the greatest difference was between the pre- and postoperative scores, and both groups improved significantly. It was concluded that the impact of the various endolymphatic sac shunts upon the symptoms in patients with Meniere's disease is highly unspecific, and that the 70% improvement in both our groups was most likely caused by a placebo effect. The patients have now been regularly followed for a minimum of 3 years and the symptoms registered whenever present. The results of hearing tests, the patients' own evaluation, and the investigator's evaluation (while still unaware of the type of operation in each patient) show that the 3-year results are the same as our results from the first year: no significant difference could be found between the two groups.

Two versus seven days penicillin treatment for acute otitis media. A placebo controlled trial in children.

103 children between 1 and 10 years of age participated in a double-blind placebo-controlled trial testing the effect of penicillin-V, 55 mg/kg/day, for two days versus seven days in acute otitis media. No significant differences could be demonstrated with regard to earache, healing of the tympanic membrane, tympanometry, fever or common cold symptoms. 76% in the group treated for seven days had a satisfactory course of the disease, compared to 71% in the group treated for two days (p greater than 0.1). In spite of the relatively small number of patients, it is concluded that the effect of penicillin for additional five days in acute otitis media after the initial treatment for two days, can at most be marginal. The advantages of a shortened treatment period are several; the authors have outlined a new treatment modality, consisting of masterful inactivity for 8-12 hours, penicillin-V for two days, and myringotomy in refractory cases, after a new evaluation by the otologist. We believe hereby to be able to reduce penicillin consumption in children with acute otitis media to about 15% of the previous level, without increasing the risk of serious complications.

Placebo effect in surgery for Meniere's disease: three-year follow-up.

In 1981 we published the results of a double-blind, placebo-controlled study in which the efficacy of a regular endolymphatic sac mastoid shunt was compared with a purely placebo operation (mastoidectomy) in controlling the symptoms of 30 patients with typical Meniere's disease. Minor differences could be demonstrated between the shunt and the sham operation, but the greatest difference was between the preoperative and postoperative scores, and both groups improved significantly. It was concluded that the impact of the various endolymphatic sac shunts on the symptoms of patients with Meniere's disease is nonspecific, and that the 70% improvement in both groups was most likely caused by a placebo effect. At the time of the presentation, the results were based on a 1-year follow-up of all patients. As of January 1982 the patients had been followed for a minimum of 3 years. The 3-year results are the same as our results from the first year: no significant difference could be found between the two groups.

Evoked acoustic emissions from the human ear. III. Findings in neonates.

Stimulated acoustic emissions were recorded in a consecutive series of 20 full-term and otherwise normal neonates with the equipment and method previously used in adults. One ear randomly chosen was tested in each baby, and otoscopy and tympanometry were normal in all ears. A 2 kHz click stimulus was presented with a repetition rate of 10/sec and the recordings were performed at three intensities, i.e. 70, 50 and -20 dBatt (dBatt approximately dB p.e. SPL). The 50 dB recording was repeated for check of reproducibility. A clear and reproducible response could be identified from all ears at 50 dBatt. However, as in the adults, the response pattern differed significantly from one ear to another, both regarding the number of 'echoes', their latencies, response amplitudes, and frequency content. The 'echo' group latencies and amplitudes were within the same range as in normal adults and the amplitude input-output curves exhibited a clear non-linearity. The relationship between latency and frequency was just as ambiguous as in the adults. Also, in the neonates, the cross correlation analysis proved to be an efficient method to indicate whether or not a true response was present. The results from this investigation are compared with those described in the literature from other audiological tests and it is concluded that the recording of the stimulated acoustic emissions could be applicable as a screening procedure in newborns.

Evoked acoustic emissions from the human ear. I. Equipment and response parameters.

Using signal averaging technique, stimulated acoustic emissions can be recorded from the human ear with a probe in the external ear canal. An acoustic click stimulus was used, produced by half a sinusoid of 2 kHz with the polarity corresponding to the rarefaction mode. A number of different techniques were developed in order to evaluate the latency and configuration of the emissions objectively. Recordings from a normal-hearing subject served as an example and a clear response could be traced down and below the psychoacoustic threshold. The threshold was elevated and the response pattern altered when a sensorineural hearing loss was induced by ingestion of acetylsalicylate. No response could be recorded from a deaf ear with an intact eardrum and a mobile ossicular chain.