Further audiovestibular characterization of DFNB77, caused by deleterious variants in LOXHD1, and investigation into the involvement of Fuchs corneal dystrophy.

This study focuses on further characterization of the audiovestibular phenotype and on genotype-phenotype correlations of DFNB77, an autosomal recessive type of hearing impairment (HI). DFNB77 is associated with disease-causing variants in LOXHD1, and is genetically and phenotypically highly heterogeneous. Heterozygous deleterious missense variants in LOXHD1 have been associated with late-onset Fuchs corneal dystrophy (FCD). However, up to now screening for FCD of heterozygous carriers in DFNB77 families has not been reported. This study describes the genotype and audiovestibular phenotype of 9 families with DFNB77. In addition, carriers within the families were screened for FCD. Fifteen pathogenic missense and truncating variants were identified, of which 12 were novel. The hearing phenotype showed high inter- and intrafamilial variation in severity and progression. There was no evidence for involvement of the vestibular system. None of the carriers showed (pre-clinical) symptoms of FCD. Our findings expand the genotypic and phenotypic spectrum of DFNB77, but a clear correlation between the type or location of the variant and the severity or progression of HI could not be established. We hypothesize that environmental factors or genetic modifiers are responsible for phenotypic differences. No association was found between heterozygous LOXHD1 variants and the occurrence of FCD in carriers.

Discrimination of speech sound contrasts determined with behavioral tests and event-related potentials in cochlear implant recipients.

Cortical potentials evoked with speech stimuli were investigated in ten experienced cochlear implant (CI, type Nucleus 24M) users using three different speech-coding strategies and two different speech contrasts, one vowel (/i/-/a/) and one consonant (/ba/-/da/) contrast. On average, results showed that, compared to subjects with normal hearing, P300 amplitudes were smaller; however, most latencies were within the normal range. Next, individual P300 measures in response to the two speech contrasts were compared to behavioral discrimination scores. Significant within-subject differences in P300 amplitudes and latencies were found for the three speech coding strategies. These differences were in agreement with the behavioral, strategy-dependent discrimination of the speech contrasts.

Vestibular function and temporal bone imaging in DFNB1.

DFNB1 is the most prevalent type of hereditary hearing impairment known nowadays and the audiometric phenotype is very heterogeneous. There is, however, no consensus in literature on vestibular and imaging characteristics. Vestibular function and imaging results of 44 DFNB1 patients were evaluated in this retrospective study. All patients displayed a response during rotational velocity step testing. In 65% of the cases, the caloric results were within normal range bilaterally. The video head impulse test was normal in all patients. In 34.4% of the CT scans one or more temporal bone anomalies were found. The various anomalies found, were present in small numbers and none seemed convincingly linked to a specific DFNB1genotype. The group of DFNB1 patients presented here is the largest thus far evaluated for their vestibular function. From this study, it can be assumed that DFNB1 is not associated with vestibular dysfunction or specific temporal bone anomalies.

Percutaneous titanium implantation in the skull for the bone-anchored hearing aid.

In the 1980s, a new type of bone conduction hearing aid was developed in Göteborg, Sweden. With this new bone-anchored hearing aid (BAHA) system, sound waves are transmitted directly to the skull by means of a titanium screw implanted into the skull. The advantages and disadvantages of the conventional hearing aid and the BAHA are described here. In the 25 patients presented, all the percutaneous implants remained firmly anchored in the skull. One screw was lost through trauma. The scores on the speech recognition-in-noise and the speech recognition-in-quiet tests were significantly higher in 64% and 32% of the patients with a BAHA, respectively.

Binaural application of the bone-anchored hearing aid.

Most, but not all, hearing-impaired patients with air conduction hearing aids prefer binaural amplification instead of monaural amplification. The binaural application of the bone conduction hearing aid is more disputable, because the attenuation (in decibels) of sound waves across the skull is so small ( 10 dB) that even one bone conduction hearing aid will stimulate both cochleas approximately to the same extent. Binaural fitting of the bone-anchored hearing aid was studied in three experienced bone-anchored hearing aid users. The experiments showed that sound localization, and speech recognition in quiet and also under certain noisy conditions improved significantly with binaural listening compared to the monaural listening condition. On the average, the percentage of correct identifications (within 45 degrees ) in the sound localization experiment improved by 53% with binaural listening; the speech reception threshold in quiet improved by 4.4 dB. The binaural advantage in the speech-in-noise test was comparable to that of a control group of subjects with normal hearing listening monaurally versus binaurally. The improvements in the scores were ascribed to diotic summation (improved speech recognition in quiet) and the ability to separate sounds in the binaural listening condition (improved sound localization and improved speech recognition in noise whenever the speech and noise signals came from different directions). All three patients preferred the binaural bone-anchored hearing aids and used them all day.

[A hearing aid anchored in the cranial bone for amplification of bone conduction]. / Een in het schedelbeen verankerd hoortoestel voor versterking van de beengeleiding.

The purpose of this study was to compare hearing and understanding with a bone conduction hearing aid of a new type and with conventional models. The new instrument, BAHA (bone anchored hearing aid) is connected with the skull percutaneously rather than transcutaneously as with the conventional instruments. In the ENT department of Nijmegen University Hospital the understanding of speech with both types of hearing aid was evaluated thoroughly. The patients had a middle-ear loss with in addition an inner-ear loss of 60 dBHL at most. A conventional air conduction hearing aid (behind or inside the ear) was unsuitable for them because of, for instance, chronic runny ears or anomalies of the auditory meatus. A conventional bone conduction hearing aid containing a transducer pressing on the skin was rejected because of poor understanding or serious side effects such as headache and pressure pains. At the first session a titanium screw was implanted in the skull behind the ear. The percutaneous superstructure was put into place a few months later at a second session. In none of the patients were there peroperative problems or postoperative infections of any importance. Understanding of speech in silence and in noise was evaluated with the BAHA and with the conventional aid. Differences in understanding of speech were regarded as significant if they amounted to more than twice the known intra-individual standard deviation. As to understanding of speech in silence, 7 of the 15 patients were found to understand significantly better with the BAHA than with a conventional aid. In the other patients no difference was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Progressive hereditary hearing impairment caused by a MYO6 mutation resembles presbyacusis.

Since deafness is the most common sensorineural disorder in humans, better understanding of the underlying causes is necessary to improve counseling and rehabilitation. A Dutch family with autosomal dominantly inherited sensorineural hearing loss was clinically and genetically assessed. The MYO6 gene was selected to be sequenced because of similarities with other, previously described DFNA22 phenotypes and a pathogenic c.3610C > T (p.R1204W) mutation was found to co-segregate with the disease. This missense mutation results in a flat configured audiogram with a mild hearing loss, which becomes severe to profound and gently to steeply downsloping later in life. The age-related typical audiograms (ARTA) constructed for this family resemble presbyacusis. Speech audiometry and results of loudness scaling support the hypothesis that the phenotype of this specific MYO6 mutation mimics presbyacusis.

Hearing with the bone-anchored hearing aid (BAHA, HC 200) compared to a conventional bone-conduction hearing aid.

Sixteen patients have been fitted with a standard bone-anchored hearing aid (HC 200), to replace their conventional bone-conduction aid. The average pure tone threshold at 0.5, 1 and 2 kHz varied from 35 to 75 dB HL, with a sensorineural component varying from 0 to 30 dB HL. The patients' performance with the bone-anchored aid was compared to that with the conventional bone-conduction aid in an acoustic-free field. The maximum phoneme score in quiet was 100% in most patients; in 6 patients, the score with the bone-anchored aid was better (range from 5 to 10%). The speech-in-noise ratio was significantly better in 11 patients (range from -1.4 to -8 dB). None of the patients had poorer results on either test with the bone-anchored aid. The improved speech recognition was ascribed to better performance of the hearing aid in the higher frequency range (above 2 kHz) and to relatively less distortion.

Use of the event-related P300 potential in cochlear implant subjects for the study of strategy-dependent speech processing.

The present overview is a compilation of the results of several event-related potential (ERP) studies on auditory cortical processing, performed in the Evoked Potential Laboratory of the University Medical Centre of Nijmegen. To study speech perception performance in cochlear implant (CI) subjects, ERPs were obtained from subjects with poor and moderate performance. The present report describes the relationships between speech-coding strategies, the presentation of speech by the CI processor, the P300 potential as a measure of speech discrimination, time effects in the long term and speech recognition in relation to ERPs.

Speech-evoked cortical potentials and speech recognition in cochlear implant users.

Processing in the auditory cortex may play a role in the unexplained variability in cochlear implant benefit. P300 and N1/P2 were elicited in post-lingually deaf cochlear implant users wearing a Nucleus multichannel cochlear implant. Four sound contrasts were presented (500-1,000 Hz, /ba/-/da/, /ba/-/pa/ and /i/-/a/). N1 and P2 were present in all subjects for all conditions. Prolonged N1, P2 and P300 latencies were found in the cochlear implant group compared to a control group of subjects with normal hearing. Cochlear implant users show smaller amplitudes of N1 for all the speech signals as well as smaller amplitudes of P2 for the consonants compared to the controls. P300 results of the cochlear implant users were compared to behavioural results of speech recognition testing. A relation was found between P300 amplitude and magnitude for the 500-1,000 Hz and /i/-/a/ contrasts and behavioural speech recognition in cochlear implant users. The results suggest that P300 measurements are useful and have additional value to speech recognition evaluations in cochlear implant users.

The super-bass bone-anchored hearing aid compared to conventional hearing aids. Audiological results and the patients' opinions.

Twelve patients with severe mixed hearing loss (PTA ranging from 70 to 108 dB HL) were provided with the percutaneous 'super-bass HC 220' bone-anchored hearing aid (BAHA) to replace their former hearing aid. Five had previously worn an air-conduction hearing aid (behind-the-ear type, BTE) which could no longer be used because of recurrent otorrhoea; the others had previously worn a conventional (transcutaneous) bone-conduction hearing aid (CBHA) which had caused serious complaints, such as headaches or skin irritation. Free-field speech audiometry in the subgroup of patients who used to wear a CBHA revealed that the maximum intelligibility score with the BAHA was equal to or better than that obtained with the CBHA (range from 0 to +27%). In three of the five patients who used to wear a BTE, the speech scores were poorer with the BAHA than with the BTE (range from -13 to -40%). For the remaining two patients, the difference in scores was 0 and +10%. In conclusion, speech recognition with the BAHA HC220 in the patients with severe mixed hearing loss was comparable to, or better than, that with a CBHA. Compared to an air-conduction hearing aid, the results may be considerably poorer. The results of the questionnaire were in good agreement with the measurements and support the conclusions.