Effect of hearing AIDS on auditory function in infants with perinatal brain injury and severe hearing loss

Background

Approximately 2–4% of newborns with perinatal risk factors present with hearing loss. Our aim was to analyze the effect of hearing aid use on auditory function evaluated based on otoacoustic emissions (OAEs), auditory brain responses (ABRs) and auditory steady state responses (ASSRs) in infants with perinatal brain injury and profound hearing loss.

Methodology/Principal Findings

A prospective, longitudinal study of auditory function in infants with profound hearing loss. Right side hearing before and after hearing aid use was compared with left side hearing (not stimulated and used as control). All infants were subjected to OAE, ABR and ASSR evaluations before and after hearing aid use. The average ABR threshold decreased from 90.0 to 80.0 dB (p = 0.003) after six months of hearing aid use. In the left ear, which was used as a control, the ABR threshold decreased from 94.6 to 87.6 dB, which was not significant (p>0.05). In addition, the ASSR threshold in the 4000-Hz frequency decreased from 89 dB to 72 dB (p = 0.013) after six months of right ear hearing aid use; the other frequencies in the right ear and all frequencies in the left ear did not show significant differences in any of the measured parameters (p>0.05). OAEs were absent in the baseline test and showed no changes after hearing aid use in the right ear (p>0.05).

Conclusions/Significance

This study provides evidence that early hearing aid use decreases the hearing threshold in ABR and ASSR assessments with no functional modifications in the auditory receptor, as evaluated by OAEs.     

Characteristics of the hearing loss in unilateral cleft lip and palate-influence on communication

Etiology of otitis media with effusion (OME) is still unclear and often described as multi-factorial. It is very usual finding in cleft palate population. We tested relationship between the hearing level, audiometric frequencies, aging and ear side in unilateral cleft lip and palate 101 children (UCLP) and subgroups of left (UCLP)(L) and right cleft side (UCLP)(R). Group of left ears is prone to higher frequency and more severe hearing disturbances than groups of right ears, with less chance of normalizing hearing level with aging. Characteristics of hearing loss level and its improvement, in UCLP children depend of cleft type, ear side and age group.     

Genetic characteristics of recessive sensorineural hearing loss

Genetic characteristics of recessive sensorineural hearing impairment mediated by 5 recessive genes were studied. One of these is responsible for early progressive hearing loss, others causing congenital deafness. The incidence of early progressive recessive hearing loss in a population is 1:20,000, gene frequency being 0.007; the incidence of heterozygotes for this gene is 1.4%. The incidence of each of 4 forms of recessive congenital hearing loss in a population is 1.125:10,000, the frequency of these genes being 0.0106; the incidence of heterozygotes for each of these genes is 2.1%. The total frequency of all recessive genes for sensorineural hearing impairment is 0.0494 and the incidence of heterozygotes for all genes is 9.9%. The frequency of different genotypes for recessive genes specifying sensorineural hearing loss was established, based on the data obtained.     

Beta blockers and loss of hearing.

Loss of hearing in a 43 year old man during treatment with metoprolol was dose related and disappeared within a few months after the drug had been stopped. The hearing impairment was of mixed type, with an air bone gap without any disorder of the middle ear observable by conventional clinical methods. Similar scattered reports from international sources on loss of hearing during treatment with beta blockers are also presented.     

GJB2-associated hearing loss undetected by hearing screening of newborns

The hearing loss caused by GJB2 mutations is usually congenital in onset, moderate to profound in degree, and non-progressive. The objective of this study was to study genotype/phenotype correlations and to document 14 children with biallelic GJB2 mutations who passed newborn hearing screening (NHS). Genetic testing for GJB2 mutations by direct sequencing was performed on 924 individuals (810 families) with hearing loss, and 204 patients (175 families) were found to carry biallelic GJB2 mutations. NHS results were obtained through medical records. A total of 18 pathological mutations were identified, which were subclassified as eight inactivating and 10 non-inactivating mutations. p.I128M and p.H73Y were identified as novel missense GJB2 mutations. Of the 14 children with biallelic GJB2 mutations who passed NHS, eight were compound heterozygotes and 3 were homozygous for the c.235delC mutation in GJB2, and the other three combinations of non-c.235delC mutations identified were p.Y136X-p.G45E/p.V37I heterozygous, c.512ins4/p.R143W heterozygous, and p.V37I/p.R143W heterozygous. These 14 cases demonstrate that the current NHS does not identify all infants with biallelic GJB2 mutations. They suggest that the frequency of non-penetrance at birth is approximately 6.9% or higher in DFNB1 patients and provide further evidence that GJB2 hearing loss may not always be congenital in onset.     

Attenuation of noise-induced hearing loss using methylene blue

The overproduction of reactive oxygen species (ROS) and reactive nitrogen species (RNS) has been known to contribute to the pathogenesis of noise-induced hearing loss. In this study, we discovered that in BALB/c mice pretreatment with methylene blue (MB) for 4 consecutive days significantly protected against cochlear injury by intense broad-band noise for 3 h. It decreased both compound threshold shift and permanent threshold shift and, further, reduced outer hair cell death in the cochlea. MB also reduced ROS and RNS formation after noise exposure. Furthermore, it protected against rotenone- and antimycin A-induced cell death and also reversed ATP generation in the in vitro UB-OC1 cell system. Likewise, MB effectively attenuated the noise-induced impairment of complex IV activity in the cochlea. In addition, it increased the neurotrophin-3 (NT-3) level, which could affect the synaptic connections between hair cells and spiral ganglion neurons in the noise-exposed cochlea, and also promoted the conservation of both efferent and afferent nerve terminals on the outer and inner hair cells. These findings suggest that the amelioration of impaired mitochondrial electron transport and the potentiation of NT-3 expression by treatment with MB have a significant therapeutic value in preventing ROS-mediated sensorineural hearing loss.     

Compensatory processes during unilateral loss of vestibular function]

Changes in the compensation of the sequences of the unilateral loss of the labyrinthine function were studied in rabbits. Destruction of the labyrinth was accompanied by ocular nystagmus, increase of frequency of respiration and heart contractions, and EEG-activation. Investigations carried out showed these reactions to be extinguished at different time. At the late periods of labyrinthectomy a considerable asymmetry of nystagmus reaction to the angular accelerations equal in intensity, but opposite in direction was revealed. Stimulation of an intact otolith labyrinth was accompanied by the appearance of positional nystagmus. The results obtained indicated imperfection of the compensatory mechanisms during complete unilateral loss of the vestibular function.