Medical genetic evaluation for the etiology of hearing loss in children

The purpose of the medical genetic evaluation is to identify the etiology of the hearing loss. To do so requires a multidisciplinary team that includes the otolaryngologist, audiologist, medical geneticist, and radiologist. A number of tests and procedures are now available to assist in the search for the cause of hearing losses. The importance of sensitivity when providing genetic counseling is emphasized. Molecular genetics offers potential for continued progress in understanding the etiologies of hearing loss. Recent advances in this area are discussed.     

Immunological abnormalities in patients with etiology unknown sensorineural hearing loss

An immunological study was carried out in 50 patients with etiology unknown sensorineural hearing loss, including the following: 12 low tone deafness, 7 sudden deafness, 8 unilateral deafness, 7 idiopathic bilateral progressive sensorineural hearing loss and 14 other bilateral sensorineural hearing loss. Twenty-five out of 50 of the cases demonstrated immunological abnormalities. A full array immunological tests were performed with the following results. High immnunoglobulin titers showed in 18 out of 50 cases. Six cases were positive for antinuclear antibody. The anti-DNA antibody assay revealed high titers in 2 cases. Also, anti-rheumatoid factor antibody assay showed high titers in 6 cases while abnormal values of complements in serum were detected in 6 cases, though an immune complex was demonstrated in only one case. Also, it was noted that six patients with immunological abnormalities have autoimmune diseases. The above results indicated that some cases of etiology unknown sensorineural hearing loss may have an immunological link.     

Sensorineural hearing loss in patients reaching chronic renal failure in childhood

An analysis of 25 patients with carcinoids of the colon (1,94% of the amount of patients with cancer of the colon) was made. In the recent decade this disease has become 2 times more frequent. Sixteen patients had carcinoids of the rectum, 9 patients had carcinoids of the right half of the colon. Malignant carcinoids were diagnosed in 16 cases, 8 of them being located in the right half. Radical operations are recommended for all carcinoids of the right half of the colon and for tumors of the rectum if more than 2 cm.     

Cigarette smoking and hearing loss: the epidemiology of hearing loss study

CONTEXT: Clinical studies have suggested that cigarette smoking may be associated with hearing loss, a common condition affecting older adults. OBJECTIVE: To evaluate the association between smoking and hearing loss. DESIGN: Population-based, cross-sectional study. SETTING: Community of Beaver Dam, Wis. PARTICIPANTS: Adults aged 48 to 92 years. Of 4541 eligible subjects, 3753 (83%) participated in the hearing study. MAIN OUTCOME MEASURES: The examination included otoscopy, screening tympanometry, and pure-tone air-conduction and bone-conduction audiometry. Smoking history was ascertained by self-report. Hearing loss was defined as a pure-tone average (0.5, 1, 2, and 4 kHz) greater than 25-dB hearing level in the worse ear. RESULTS: After adjusting for other factors, current smokers were 1.69 times as likely to have a hearing loss as nonsmokers (95% confidence interval, 1.31-2.17). This relationship remained for those without a history of occupational noise exposure and in analyses excluding those with non-age-related hearing loss. There was weak evidence of a dose-response effect. Nonsmoking participants who lived with a smoker were more likely to have a hearing loss than those who were not exposed to a household member who smoked (odds ratio, 1.94; 95% confidence interval, 1.01-3.74). CONCLUSIONS: These data suggest that environmental exposures may play a role in age-related hearing loss. If longitudinal studies confirm these findings, modification of smoking habits may prevent or delay age-related declines in hearing sensitivity.     

The etiology of idiopathic sudden sensorineural hearing loss. Experimental herpes simplex virus infection of the inner ear

PURPOSE: To evaluate dimercaptosuccinic acid (DMSA) scintigraphy and urography in the detection of renal involvement in children with urinary tract infection (UTI) in order to identify patients with a high risk of developing renal damage. MATERIAL AND METHODS: A total of 157 children (median age 0.4 years, range 5 days to 5.8 years) with first-time symptomatic UTI were examined scintigraphy (with an assessment of renal area involvement) and urography at the time of UTI and 1 year later. All evaluations were made blindly. RESULTS: Of the total 314 kidneys, 80 (25%) were abnormal at initial scintigraphy. Of these 80 kidneys, 44 (55%) had normalized at follow-up. Of the 234 initially normal kidneys, 29 (12%) were abnormal at follow-up. One year after UTI, abnormalities were seen in 59 children at scintigraphy and in 18 children at urography. Renal area involvement was larger and split function abnormalities more common in kidneys that were abnormal at both scintigraphy and urography than in kidneys with only scintigraphic abnormalities. CONCLUSION: Quantitation of renal area involvement and split renal function at early scintigraphy would seem to be useful in identifying patients at risk of developing renal damage. Urography at 1 year after infection identified mainly those with the most severe scintigraphic abnormalities. The clinical importance of scintigraphic abnormalities that are not confirmed by urography is not known.     

Mitochondrial DNA mutation at nucleotide 1555 in a patient with bilateral sensorineural hearing loss of unknown etiology

A mitochondrial DNA mutation at nucleotide 1555 in the ribosomal RNA gene was recently reported as a cause of maternally inherited non-syndromic sensorineural deafness. We assumed that the 1555 mutation is also associated with sporadic non-syndromic deafness and screened for the mutation in seven randomly selected sporadic cases with bilateral sensorineural hearing loss of unknown etiology. The mutation was found in one patient, who first noticed hearing loss when she was in her early teens with subsequent gradual progression. The results suggest that the 1555 mutation may contribute to the etiology of idiopathic bilateral sensorineural hearing loss in some cases.     

The etiology of childhood spider phobia

Twenty-six girls with a clinical spider phobia and 26 matched control girls were interviewed about conditioning, modeling, and negative information experiences in connection with spiders. In addition, parents of the phobic girls were independently interviewed about the origins of their child's phobia. Phobic children more often reported aversive conditioning experiences with spiders than did control children. Also, in a number of cases, conditioning events described by the phobic children were confirmed by their parents, a result that replicates the findings of Merckelbach, Muris and Schouten (1996; Behaviour Research and Therapy, 34, 935-938). Taken together, the results contradict a strong version of the non-associative account of phobias and suggest that in at least some cases, conditioning events may contribute to the development of (childhood) spider phobia.     

Pathophysiological mechanisms of hearing loss

An understanding of auditory transduction in the ear can contribute to a better comprehension of the pathophysiological mechanisms which give rise to hearing loss. The incoming sound sets up a mechanical traveling wave which begins at the base and progresses along the basilar membrane, reaching a point of maximal displacement. The region of maximal displacement is a function of stimulus frequency. The mechanical displacement, by directly opening ion channels in the stereocilia of the hair cells, induces changes in the electrical potential of the hair cells. This initial stage is called mechano-electrical transduction, and in the normal ear, is followed by a stage of electro-mechanical transduction based on the ability of the outer hair cells to respond to the electrical changes induced in them with a change in their length. This "electromotility" presumably provides mechanical feedback to the basilar membrane, augmenting its mechanical displacement. This is called the cochlear amplifier, providing the ear with improved sensitivity and frequency discrimination. Most forms of sensori-neural hearing losses (affecting the inner ear) are due to a lesion to some part of this cochlear amplifier (e.g. noise induced hearing loss, ototoxic drugs) and are therefore characterized by auditory threshold elevations and poorer frequency discrimination.     

Effect of a hearing aid on progressive hearing loss

A group of 72 children with hearing aids followed in 4 different clinical settings presented progressive increase in sensorineural hearing loss. The mean hearing loss over time, the duration of hearing aid use and the gain were studied to test the hypothesis that continued progression in hearing loss was due to overly powerful amplification. No correlation was found between the progressive increased gain levels were associated with less progression in hearing loss than at lower gain levels. Therefore, the use of hearing aids was not directly and significantly related to the increase in hearing loss in the population studied. However according to the above criteria a few cases (4%) of progressive hearing loss did seem to be associated with hearing aid use.     

Viral etiology of intussusception in Taiwanese childhood

The T-agglutination types were determined for a diverse collection of 1531 group A streptococci for which the 5' M protein gene (emm) sequences had been analysed. The majority of the T-agglutination types correlated with previously seen M/emm/T-type associations; however, several new associations were found. Analysis of a subset of this collection -- which included 1157 clinical isolates with multiply encountered emm types -- found that emm amplicon restriction profiles of isolates sharing identical T types and opacity factor phenotypes are useful for detecting groups of isolates with identical emm genes. Many emm genes of known 5' sequence display a highly conserved restriction pattern amongst clinical isolates widely separated both geographically and temporally.     

Osteogenesis imperfecta and hearing loss

In the present study, experimental exposures to hyperbaric oxygen (HBO) were performed (30-min exposure to 2.8 bar pure oxygen). During all phases of the experiment the electroencephalogram (EEG) was recorded continuously for on-line visual monitoring and off-line quantitative analysis. Conventional and quantitative EEG findings are described for a group of 23 subjects during an uncomplicated HBO exposure and for one subject who had a generalized tonic-clinic seizure when exposed to HBO. In the group of subjects who did not show signs of toxicity, EEG changes were minor and were not considered indicative of an adverse effect of HBO on the brain during the HBO exposure. Pre-convulsive EEG changes were detected in the subject with the seizure but were too insignificant for practical monitoring purposes and did not clearly herald clinical signs.     

R-phenylisopropyladenosine attenuates noise-induced hearing loss in the chinchilla

Reactive oxygen species, which are cytotoxic to living tissues, are thought to be partly responsible for noise-induced hearing loss. In this study R-phenylisopropyladenosine (R-PIA), a stable non-hydrolyzable adenosine analogue which has been found effective in upregulating antioxidant enzyme activity levels, was topologically applied to the round window of the right ears of chinchillas. Physiological saline was applied to the round window of the left ears (control). The animals were then exposed to a 4 kHz octave band noise at 105 dB SPL for 4 h. Inferior colliculus evoked potential thresholds and distortion product otoacoustic emissions (DPOAE) were measured and hair cell damage was documented. The mean threshold shifts immediately after the noise exposure were 70-90 dB at frequencies between 2 and 16 kHz. There were no significant differences in threshold shifts at this point between the R-PIA-treated and control ears. By 4 days after noise exposure, however, the R-PIA-treated ears showed 20-30 dB more recovery than saline-treated ears at frequencies between 4 and 16 kHz. More importantly, threshold measurements made 20 days after noise exposure showed 10-15 dB less permanent threshold shifts in R-PIA-treated ears. The amplitudes of DPOAE also recovered to a greater extent and outer hair cell losses were less severe in the R-PIA-treated ears. The results suggest that administration of R-PIA facilitates the recovery process of the outer hair cell after noise exposure.     

Update--noise induced hearing loss and the military environment

Quality clinical experiences are a critical component of advanced practice nursing (APN) curricula. Historically, nursing instructors coordinated both the didactic and clinical components of a course. Increasingly, course coordinators organize the didactic component, and external preceptors working in the clinical setting function as practicum teachers. Both scenarios involve labor-intensive processes, and neither facilitate the scheduling of clinical experiences that build on progressive learning across the student's curriculum. A centralized, computerized, relational data base for efficient management of APN preceptors and students across the curriculum was designed. One master's-prepared clinical coordinator maintains the data base and performs all related functions. This system offers numerous benefits to students, preceptors, ] faculty, and nursing school, including balanced and progressively complex clinical learning experiences for students from competent preceptors: consistent interface with students and preceptors; faculty relief from time-consuming tasks; rapid generation of a variety of tables, rosters, and reports; consistent tracking of preceptor evaluations; timely acknowledgment of preceptor assistance; and efficient communication among students, preceptors, faculty, and school administration.     

Implantable hearing devices for sensorineural hearing loss: a review of the audiometric data

BACKGROUND: Child fatality review (CFR) by interagency teams can contribute to the prevention of childhood deaths. We investigated the potential usefulness of Georgia's CFR, legislated in 1990 primarily to prevent death from child maltreatment, for identifying preventable deaths from injury and sudden infant death syndrome (SIDS). METHODS: Using CFR report data and death certificate data, we examined reviewed and nonreviewed childhood deaths in Georgia in 1991 and examined data by etiology, county, risk factors, and preventability. RESULTS: Injury or SIDS caused 33.2% of childhood deaths in Georgia in 1991; CFR reviewed 29.4% of these. Child fatality review was most sensitive for investigating death from intentional injury (40.5%) and SIDS (35.3%). Review teams reassigned the cause of five deaths (2.0%) to child abuse or neglect. County participation was low (31.4%). Overall, 29.0% of deaths were judged preventable. CONCLUSIONS: Georgia's CFR has potential for identifying preventable childhood deaths. Refinements in the system can increase the number and accuracy of death investigations. By participating in the system, physicians may make meaningful contributions to preventing childhood death in their own communities.     

Noise and hearing loss in firefighting

Since the NIH received a request to investigate the high degree of hearing loss in a fire department in 1980, hearing loss among firefighters has become an area of increased investigation. The author identifies the sources of occupational noise in firefighting, looks at audiometric testing and recent research in firefighting noise, and presents guidelines for implementing hearing conservation programs.     

Occupational lead exposure and hearing loss

Studies of adults, children, and laboratory animals suggest an association between lead exposure and hearing loss. A causal relationship might direct mandated medical surveillance of lead-exposed workers to include audiometric testing. A cross-sectional, computerized dataset was obtained from a private occupational health screening company to examine the relationship between blood lead level and hearing loss. Audiometry and blood lead results were available for 183 workers. A statistically significant correlation was found between blood lead level and an elevated hearing threshold at 400 Hz (P = 0.03); no other frequencies showed such a correlation. This finding suggests either an interaction between nose exposure and lead, interaction of other exposure factors (such as cigarette smoking), or that factors other than biomechanical ones render the organ of Corti more susceptible at 4000 Hz. Further evaluation of these questions should be undertaken. Computerized databases created for worker surveillance may be a source for data useful for examining other causal connections in occupational settings.     

Paediatric hearing loss in rural Pakistan

OBJECTIVE: The present study was designed to generate population-based data on the prevalence and causes of hearing loss in rural Pakistani children. A community screening programme was utilized to identify and evaluate the hearing impaired. METHODS: The study was performed in conjunction with the Ministry of Population Welfare in Sialkot District, Punjab Province. School-aged children between the ages of 5 and 15 years were screened and examined for hearing impairment according to World Health Organization (WHO) protocols. Case-control analysis of audiometric, physical examination, and risk factors for hearing loss were performed, followed by chi-square analyses. RESULTS: A total of 607 children comprised the study population, with an overall point prevalence of hearing impairment of 7.9%. Fifty percent of all hearing loss was conductive in nature, amenable to either medical or surgical therapy. The risk factors most associated with conductive hearing loss were otorrhea and multiple ear infections greater than 5. In cases of severe hearing loss, 70% were the result of consanguinous marriages. Almost no cases of hearing loss were attributable to measles, mumps, rubella, and the TORCH infections. CONCLUSION: This study has generated some badly needed population-based data on the magnitude of the problem of hearing loss in rural Pakistan. It is hoped that the results of this work will stress the importance of hearing health in Pakistan and to encourage other professionals to pursue similar projects.