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Biomedical subjects

N J Johnsen

Publications and source records attributed to N J Johnsen.

At least 19 recordsLinked to original sources
PubMed1993

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.

Adolescent↗
PubMed1992

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.

Acoustic Stimulation↗
PubMed1991

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.

Acute Disease↗
PubMed1991

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.

Adolescent↗
PubMed1989

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.

Child, Preschool↗
PubMed1989

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.

Adult↗
PubMed1988

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)

Audiometry, Evoked Response↗
PubMed1985

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.

Adult↗
PubMed1984

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.

Adult↗
PubMed1983

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.

Adult↗
PubMed1983

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.

Acoustic Stimulation↗
PubMed1982

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.

Acoustic Stimulation↗
PubMed1982

Evoked acoustic emissions from the human ear. II. Normative data in young adults and influence of posture.

Click-evoked acoustic emissions were recorded in 10 normally hearing young adults and evaluated by methods previously described. Five of the subjects were tested on both ears. A clear response could be traced down to or below the psychoacoustic threshold in all ears. However, the response pattern differed significantly from one ear to another, yielding an intra- and intersubject variability of the same order of magnitude. The key parameter of the evoked emission seems to be the group latency, since both peak-to-peak amplitude and frequency content are defined only at a specific latency. Two methods were applied to establish group latencies objectively and the two latency measures were almost identical. The individual input-output functions, based on peak-to-peak amplitude values as well as RMS values, exhibited nonlinearity. The latency versus frequency relationship was ambiguous. Retests of five ears at 4-5 week intervals demonstrated a high stability of the response pattern from the individual ear. Five subjects were tested in the sitting as well as in the recumbent position and the response pattern were unaffected by posture.

Acoustic Impedance Tests↗