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M P Brocaar

Publications and source records attributed to M P Brocaar.

34 records · Page 2Linked to original sources
PubMed1988

Brainstem response audiometry. II. Classification of hearing loss by discriminant analysis.

In the companion paper [V.d. Drift et al.; Audiology 27: 260-270, 1988], it was shown graphically that conductive and cochlear hearing loss can be distinguished on the basis of the combinations of the auditory brainstem response threshold with the horizontal shift of the latency-level curve of peak V, its derivative or the latency of peak V at threshold level, respectively. In addition to the patient data used in the companion paper, 22 patients with mixed hearing loss were enrolled in the present study. The statistical technique of discriminant analysis was applied to find the optimum linear combination of auditory brainstem response data for classification of a hearing loss. The brainstem classification 'cochlear hearing loss' agrees with the diagnosis on the basis of the pure-tone audiogram in 85% of the cases. In cases with the brainstem classification 'conductive hearing loss', 93% showed at least a conductive component in the pure-tone audiogram.

Adolescent↗
PubMed1988

Brainstem electric response audiometry in preterm infants.

In the Sophia Children's Hospital in Rotterdam 108 preterm infants were examined with Auditory Brainstem Response (ABR). Ears were categorized as 1) normal sensitivity for post-conceptional age (PCA), 2) probably-mild loss of sensitivity, or 3) a moderate to severe loss of sensitivity. All infants showed ABR peaks, so no "deaf" individuals were found. A bilaterally normal sensitivity was found in 61. A probably-mild loss was found in 22 infants and a moderate to severe loss in 21 infants. The type of loss was conductive in 31 and cochlear in 12. A moderate to severe bilateral cochlear loss was found in 2. This is in line with the literature. Of the 43 infants with a (probable) loss 18 were examined again at 3 months corrected age. Only half of the conductive losses had disappeared, the other half was exacerbated. About 2 out of 3 initially moderate to severe losses were confirmed at follow-up. The moderate to severe losses of the cochlear type were all confirmed.

Audiometry, Evoked Response↗
PubMed1987

The relation between the pure-tone audiogram and the click auditory brainstem response threshold in cochlear hearing loss.

Auditory brainstem response thresholds for 209 ears with cochlear hearing loss were compared with the pure-tone thresholds. It is shown that the pure-tone threshold in the 2- to 4-kHz region has a one-to-one relationship with the auditory brainstem response threshold. Estimating the pure-tone threshold from the auditory brainstem response threshold, the standard error of the estimate is 11 dB. A small part of this estimation error is due to errors in the measurement of the auditory brainstem response threshold and the mean of the pure-tone thresholds at 2 and 4 kHz. The major part is due to unknown factors that are involved in the physiological relationship between the two thresholds.

Audiometry↗
PubMed1985

Methods of analysis of large numbers of audiograms.

The analysis of large numbers of audiograms raises the question if and how we can reduce the amount of data without discarding essential information. The present paper compares two ways of data reduction: principal-component analysis and curve fitting. The methods are tested on the audiograms of a large family suffering from a dominant hereditary, progressive hearing loss, beginning in the high frequencies. It is shown that principal-component analysis rejects information on the shape of the audiogram, as do all methods generally referred to as factor analysis. The information concerned is essential for our understanding of the patient's ability to discriminate speech. Curve-fitting procedures are shown to be effective in data reduction.

Audiometry↗
PubMed1985

Follow-up study in a family with dominant progressive hereditary sensorineural hearing impairment. I. Analysis of hearing deterioration.

An autosomal-dominant progressive hereditary sensorineural hearing loss with onset in the high frequencies was studied in a Dutch family with 105 affected individuals. The hearing loss was analyzed by a curve-fitting procedure. A hyperbolic tangent was fitted into the audiogram. Five characteristics were distinguished: the high-frequency plateau, the low-frequency plateau, the slope, the low cut-off frequency and the high cut-off frequency. Six phases are recognizable in the development of the hearing loss, which is characterized by a two-step progression, first in the high and then in the low frequencies. Great differences in the rate of the deterioration were observed. The age of onset is between 5 and 15 years.

Age Factors↗
PubMed1985

Follow-up study in a family with dominant progressive hereditary sensorineural hearing impairment. II. Clinical aspects.

An autosomal-dominant progressive sensorineural hearing loss in six generations of a large family with 105 affected members was studied. The pattern of inheritance is autosomal dominant with an almost complete penetrance. The age of onset is between 5 and 15 years. Individuals with a normal audiogram at the age of 15 and over will not develop the disorder. Different generations show an identical pattern of progression. Because the age of onset is the same, anticipation is excluded. The hearing loss is symmetrical. Over 40 years, low-frequency losses are greater in females than in males. Epistasis possibly plays a role since affected individuals in branch II of this family have a more severe expression than those in the other two affected branches. No abnormal excretion of organic acids in the urine could be established.

Adolescent↗
PubMed1985

Investigations of the residual hearing capacity of severely hearing-impaired and profoundly deaf subjects.

Speech reception functions (maximum discrimination score for phonemes, speech reception threshold) and auditory functions (pure-tone audiogram, difference limens for frequency and intensity, temporal modulation transfer function, critical ratio and temporal integration) have been investigated in a group of severely hearing-impaired and deaf subjects (median Fletcher index: 80 dB), for different frequency regions (250, 1 000 and 2 000/4 000 Hz). The correlations between the different functions were calculated on the basis of characteristic numbers, derived from the originally measured functions, in the indicated frequency regions. The residual hearing capacities could be described best with two factors, one reflecting the distortion term in the speech reception threshold and the other representing the frequency discrimination for high-frequency tones. It was found that residual hearing capacities are present, at least up to a Fletcher index of 105 dB.

Adolescent↗
PubMed1984

Analysis of hearing loss due to cis-diamminedichloroplatinum-II.

The difference in the hearing threshold before and after treatment with cis-diaminnedichloroplatinum (DDP) is analysed in 69 patients. Hearing loss due to DDP treatment is mainly limited to 8,000 Hz and the incidence is about 40%. The effect of DDP is dose-related, although even at the lowest dose 20% of the patients are affected. The age of the patients is not an important factor. Loss of hearing due to DDP treatment occurs independent of any pre-existent hearing loss although those patients with great pre-existent hearing loss do not show a further loss. Of the patients with hearing loss, 39% show a difference of 20 dB or more between the left and the right ear. Hearing loss due to DDP is of minor importance compared with many of the other side-effects of DDP.

Auditory Threshold↗
PubMed1984

Reliability of auditory function tests in severely hearing-impaired and deaf subjects.

The test-retest variability of a series of auditory functions has been investigated in a group of severely hearing-impaired and deaf subjects (64 ears, median Fletcher index: 80 dB) and in a group of 10 controls with normal hearing. An adaptive forced-choice procedure was used for both groups. The functions were: tone audiogram, difference limen for intensity, difference limen for frequency, modulation transfer function and critical ratio. In spite of sometimes strongly deviating function values within the hearing-impaired group, the test-retest variability of the two groups was found to be of the same order of magnitude, except for the tone audiogram where the variability in the hearing-impaired group was twice that for the control group.

Adolescent↗
PubMed1984

Frequency-specific auditory brainstem responses to clicks masked by notched noise.

Frequency-specific auditory brainstem responses were recorded as a function of the intensity of a click masked by notch-filtered white noise (i.e. band-stop-filtered). The bandwidth of the notch was fixed at five-thirds octave and the center frequency was 0.5, 1.0, 2.0 or 4.0 kHz. For normally hearing subjects the latency of the main peak in the responses is increasing with decreasing center frequency of the notch and with decreasing click intensity. At a click sensation level of 60 dB, the mean of 7 subjects' peak latency was 6.7 ms for the center frequency 4.0 kHz and 10.2 ms for the center frequency 0.5 kHz. The thresholds derived from the frequency-specific responses were within 20 dB above the subjective thresholds of audibility of the clicks as heard when masked by notched noise.

Adult↗
PubMedDate not supplied

The masked threshold to noise ratio in brainstem electric response audiometry: assessment of the conductive loss component by bone-conducted masking.

The aim of this study was to assess the conductive loss component (CLC) by brainstem electric response audiometry. A bone-conducted noise was used to mask out the response to a conventional air-conducted click stimulus. The difference between the levels of the click and the noise is defined as the masked threshold to noise ratio (MTNR). This MTNR was determined for 21 normal ears (MTNR = -13 +/- 5 dB). The increase in MTNR compared to this normative value is a measure of the CLC. For 10 ears with an artificially induced purely conductive loss, the increase in MTNR is in good agreement with the results of conventional pure-tone and brainstem electric response audiometry.

Acoustic Stimulation↗
PubMedDate not supplied

Click-evoked oto-acoustic emissions in 1036 ears of healthy newborns.

Click-evoked oto-acoustic emissions (EOAEs) were recorded in 1036 ears of healthy newborns and in 71 normal-hearing adult ears. Newborns aged between 3 and 238 h were examined in a separate but not silent room of the obstetric ward. The adults were tested in a quiet but not sound-treated room. The recordings were more difficult in the newborn than in the adult, which was mirrored in recording parameters such as the time required for measurement (up to 7 min in newborns vs. 1-2 min in adult ears). Recording was always successful in adults, while retests were necessary in 4% of newborns. Also the artefact-rejection level and the stimulus stability were more favourable in adults. Still, EOAE recording for screening purposes in newborns seems feasible. Response levels in newborns (range 1.6-38.6; mean 20.2 dB SPL) appear to be higher than in adults (range 2.7-20.6; mean 12.8 dB SPL). The overall prevalence of EOAEs in newborns amounted to 93.4% and appeared to be age related. It rises from 78% in ears from newborns younger than 36 h to 99% in ears of newborns older than 108 h. This rise may be related to the middle ear clearance of amniotic fluid in the first days post partum. The prevalence in newborns older than 3-4 days is comparable with the prevalence of 97.2% in adults. Therefore, newborns should not be screened before the age of 4 days. In search of an objective EOAE detection variable, the prevalence of EOAEs for different age groups was calculated for various criterion values of reproducibility. These prevalences were compared to subjectively scored EOAE prevalences in the same age groups. A reproducibility criterion of about 50% appears to be useful for mass screening in newborns.

Acoustic Stimulation↗
PubMedDate not supplied

Click-evoked oto-acoustic emissions in very-low-birth-weight infants: a cross-sectional data analysis.

For the purposes of studying the phenomenon of evoked oto-acoustic emissions (EOAEs) in very-low-birth-weight (VLBW) infants, and the conditions affecting the utility of EOAE ear screening in this population, click EOAEs were repeatedly recorded in ears of 144 VLBW infants, at different postconceptional ages of the infants and at two different test sites, i.e. in the neonatal high-care unit (ward), or at the neonatal outpatient clinic. The postconceptional age of the infants examined in the ward was 30-49 weeks and 37-66 weeks for the infants examined at the outpatient clinic. Overall 840 recording attempts were done. In the ward 86% of these attempts (388) were successful against 60% (of 452 attempts) at the outpatient clinic. In the latter group of infants the success rate of recording was only 33% at the corrected age of 6 months, which is significantly less than the 66% until the corrected age of 3 months. For a cross-sectional analysis of age effects one ear of each successfully recorded infant was selected. Analysis of the 127 successful recordings revealed that the EOAE prevalence was 71% in the ward (54% for infants receiving extra oxygen per naso) and 91% at the outpatient clinic. Compared with healthy newborns, VLBW infants are much more difficult to test, especially at the outpatient clinic. However, the EOAE prevalence at this test site is the highest and approaches that in healthy newborns. At the outpatient clinic response levels of EOAEs recorded approach levels found in healthy newborns. The higher success rate of recording in the ward and the lower EOAE prevalence are two counteracting factors as to the utility of EOAE-based ear screening of VLBW infants.

Cross-Sectional Studies↗
PubMedDate not supplied

Hearing loss in students at a conservatory.

We tend not to think of music as noise but as a pleasant sound. Yet, played loud enough, music can become a threat to the human ear. The question arises whether professional musicians suffer from hearing losses caused by their playing of music. The hearing of students at the Rotterdam conservatory was studied; medical students served as a reference group. High percentages of audiometric noise dips (16%) and high-frequency losses (20%) were found in students of the conservatory, as well as a high percentage (72%) of extended high-frequency losses relative to the reference curves of Dreschler et al. Surprisingly, an equally large (and in the high-frequency region an even higher) percentage of hearing losses was found in the control group of medical students with the same median age. In sum, the exposure of conservatory students to the practice of music has as yet had no effect on their hearing.

Adolescent↗