An analysis of the aetiology of early childhood deafness

The prevalence and causes of hearing impairment in Oman: a community-based cross-sectional study

A community-based nationwide survey for hearing loss was conducted in Oman in 1996-97. Audiometric tests and ear examinations were conducted for 12,400 persons in phase I. For children aged less than 4 years, subjective screening tests were used. In phase II, otologists examined the hearing-impaired subjects to determine the cause. The prevalence of bilateral hearing impairment was 55/1000 (95% CI 51.08-59.47). Gender difference was not significant. The rates were 325/1000 and 17/1000, respectively, in the > or = 60-year and < 10-year age groups. Presbyacusis and middle ear diseases, respectively, were the causes of 33% and 20% of bilateral hearing impairment. In 30% of the bilateral hearing-impaired subjects, the cause could not be determined. The prevalence of bilateral disabling hearing loss was 21/1000 (95% CI 18.07-23.29). Noise-induced trauma was responsible for only 1.4% of cases of disabling hearing loss. Establishing primary ear care, introducing hearing screening for neonates and schoolchildren, promoting safe preventive practices for ear care, strengthening secondary-level ear care services and introducing comprehensive rehabilitative initiatives for the hearing-disabled are recommended to reduce the hearing loss rates.

Causes of severe to profound deafness in Omani paediatric population

The study includes a retrospective analysis of causes of deafness in 1400 Omani children who were detected to be suffering from severe to profound levels of hearing impairment. A standard form was used to collect various details from the otolaryngologists all over the country. The time period included is from 1986 to 2000. The rate of consanguineous marriage in the parents of the affected children was 70%, and 67.8% of these children had a sibling suffering from hearing impairment. There has been a rapid evolution of the antenatal, perinatal and neonatal care delivery in Oman during last couple of decades. The Omani paediatric population has been well covered (>90%) under the vaccination protocols including rubella. It has helped in reducing the share of infectious diseases towards the hearing impairment. The study is an attempt to identify various causes of the identifiable causes of severe to profound hearing impairment in Omani paediatric population which is the first attempt of this kind in this country. Relevant literature has been reviewed.

Evidence of Subtle Auditory Deficit in a Group of Patients Recovered from Bacterial Meningitis

OBJECTIVES

Sensorineural hearing loss of greater than 30 dB hearing loss occurs in up to 30% of patients after acute bacterial meningitis. This study investigated whether postbacterial meningitic patients with no apparent clinical sensorineural hearing loss had any evidence of more subtle subclinical cochlear deficit.

DESIGN

Prospective case-controlled clinical trial.

SETTING

Departments of Otolaryngology in Leicester and Nottingham, England, UK.

PATIENTS

Fifty-eight controls and 20 postbacterial meningitic patients aged between 18 and 38 years were screened by a questionnaire and tympanometry to exclude hearing loss attributable to other causes. All participants fell below the 90th percentile pure-tone audiometry threshold of the Lutman and Davis UK data sets.

MAIN OUTCOME MEASURES

In both ears, standard (0.25-8 kHz) pure-tone audiometry, high-frequency pure-tone audiometry (10-16 kHz), and distortion product otoacoustic emissions at 2, 4, and 6 kHz were measured.

RESULTS

Mean thresholds over the range of standard pure-tone audiometry (analyzed independently) for the postbacterial meningitic patients were significantly elevated at most frequencies (p < 0.05-p < 0.001) between 4 and 7 dB in both ears above control group values. There was no evidence of significant high-frequency threshold elevation (10-16 kHz). The mean iso-distortion product values at 2, 4, and 6 kHz were elevated in both ears in the meningitis group; significantly so (p < 0.05-p < 0.01) at all three frequencies in the right ear and at 4 kHz in the left.

CONCLUSIONS

Postbacterial meningitic patients with hearing below the 90th percentile range had a slight but significant subclinical threshold elevation over the standard pure-tone audiometry. This may reflect a real effect of the infection at the level of the cochlea, or it may be attributable to a mild residual cognitive defect. The moderate increases in iso-distortion product values are more likely to be real and reflect an effect on outer hair cell function in response to lower stimulus intensities.

Unilateral sensorineural hearing loss and its aetiology in childhood: the contribution of computerised tomography in aetiological diagnosis and management

OBJECTIVES

The objective of this study was to identify factors correlated with the CT outcome and to examine the contribution of the CT scan in the aetiological diagnosis and management of unilateral sensorineural hearing loss in childhood.

METHODS

The records of 35 consecutively investigated patients by the Audiology Department of Great Ormond Street Hospital between January 1996 and June 1998 were reviewed. The CT results, population sample characteristics, initiation of further investigations after the CT results and management decisions based on the CT results were tabulated and analysed.

RESULTS

In a series of 35 consecutively investigated children with unilateral sensorineural hearing loss, 11 CT scans were identified as abnormal. The CT findings were: labyrinthitis ossificans (3), unilaterally dilated vestibular aqueduct (2), bilaterally dilated vestibular aqueduct (2), unilateral deformity of the cochlea ('Mondini') (1), unilateral severe labyrinthine dysplasia (1), unilateral markedly narrow internal acoustic meatus (1), bilaterally dilated lateral semicircular canals (1). The presence of progressive hearing loss was a significant predictor of abnormal CT outcome, while the severity of hearing loss was not. The CT scans offered valuable information regarding the aetiological diagnosis in all cases and, in addition, prompted the appropriate vestibular rehabilitation in three cases, further investigations in four (with dilated vestibular aqueduct) and hearing preservation counselling in two (bilateral DVA) (seven out of 35 = 20%).

CONCLUSION

All children with unilateral sensorineural hearing loss should have a CT scan of the petrous pyramids/IAMs performed at some stage, as not only aetiology but also prognosis and management of these cases may be significantly influenced by the CT outcome.

Changes in prevalence, aetiology, age at detection, and associated disabilities in preschool children with hearing impairment born in Göteborg

The prevalence of hearing impairment (HI) in preschool children born in Göteborg in 1980 to 1984 was 2.0 per 1000. This was significantly lower than the 3.8 per 1000 found in a previous study for 1970 to 1974. The decrease took place in the moderate to severe range of HI, while deafness and mild HI remained unchanged during the period. The cause was considered to be prenatal in 58% with heredity in 33% as the main causative factor. Following the introduction of the MPR (Morbilli-Parotitis-Rubella) vaccination programme in Sweden, no cases of rubella- or mumps-induced HI could be found. The number of HI of perinatal origin decreased by half, in spite of the fact that the figures for preterm baby survival almost doubled during the period. Associated disabilities were diagnosed in 62% of the children with HI; speech retardation in 33%, visual abnormalities in 30%, mental retardation in 12% and neuropsychiatric disorders in 9% of the cases. The importance of collaborative efforts between the otolaryngologist and the neurologically and neuropsychiatrically interested paediatrician in the complete evaluation of additional difficulties in the HI child is emphasized.

[Hearing findings in subjects after meningitis]

INTRODUCTION

It was proposed to ascertain the occurrence of individuals who present hearing loss, due to contracting meningitis, as well as to characterize the diagnosed loss as far as the type, degree and the audiometric configuration are concerned.

MATERIAL AND METHOD

The methodology used comprised a survey of 949 references of patients attended at the Hearing Disturbance Center of the HPRLLP/USP, in order to select those who presented hearing loss after meningitis and, from the analysis of the hearing evaluation to which they were submitted, achieve the proposed goal.

RESULTS AND CONCLUSION

The results indicated a 6.2 percent occurrence as regards hearing loss due to meningitis in relation to other causes and the characteristic of this hearing loss was predominantly sensorineural, symmetrical, al linear and to a profound degree.

Risk factors for childhood sensorineural hearing loss in the Oxford region

We have used a comprehensive register of hearing-impaired children born in the former Oxford Health Region to study risk factors for sensorineural hearing loss. The occurrence of a wide variety of risk factors was documented from the case notes of 145 children; these were all the cases known at the time of the study with all degrees of hearing loss born between 1984 and 1988. Comparison with the normal Regional population showed that maternal age over 35 years and Asian ethnic origin were significant risk factors for congenital (non-acquired) hearing loss (odds ratio 1.7 and 2.5 respectively). Black/Asian children were also significantly more likely to have acquired losses. Low birthweight (below 2500 g) also gave a significantly increased risk, with an odds ratio of 4.5, rising to 9.6 for birthweight less than 1500 g. We also found that significantly more hearing-impaired cases were in lower social classes compared with the general population. A high proportion of cases (24%) had cranio-facial abnormalities (CFA), including many non-aural abnormalities and dysmorphic features, which therefore should be counted as high risk. Hearing losses acquired due to perinatal causes were almost all mild or moderate. Four factors-admission to special care baby unit for more than 72 hours, CFA, family history, and meningitis-accounted for 69% of all cases in this study. Targeted neonatal screening based on the first three factors, plus obligatory testing following meningitis, therefore, should be highly efficient at detecting deafness early.

Visual impairment in severe and profound sensorineural deafness

The frequency of reversible and irreversible visual impairment was determined in children with severe and profound sensorineural deafness, as subnormal vision can adversely affect their educational and social development. Eighty three of 87 such children attending an audiology service were examined to assess the incidence and severity of visual impairment. Each child underwent a detailed ophthalmic assessment. The criteria for visual impairment were visual acuity < 6/9 Snellen or equivalent and/or abnormal binocular vision. Forty five had a normal ophthalmic examination (54.2%). Twenty nine had visual impairment (34.9%) and nine had ophthalmological abnormalities that did not interfere with vision (10.9%). A higher proportion of children with risk factors for visual pathology demonstrated visual impairment than those in whom there were no risk factors. None the less, 44% of visual impairment was among patients without risk factors. The results underline the need to examine all children with severe and profound sensorineural deafness soon after diagnosis and indicate that children with multiple handicaps have a greater likelihood of visual impairment (11 of 14 cases).

Aetiology of deafness in children from a school for the deaf in Malaysia

One hundred and sixty-five children from the school for the deaf were screened to find out the aetiology of deafness. The screening included routine ophthalmological examination. Aetiology was unknown in 33 children (20%). Prenatal infection was found to be the cause of deafness in 61 cases (36.96%). Rubella eye signs were found in 59 children (35.76%), whereas the history of rubella infection during the first trimester of pregnancy was found in only 33 of these cases (55.93%). Perinatal complications were seen in 20 children (12.12%). Twenty children (12.12%) had meningitis during their early childhood period. Routine ophthalmological examination helped us to pick up cases with rubella eye signs. Ophthalmological examination should be included as part of any study done to find out the cause of deafness.

Clinical and genetic heterogeneity in X-linked deafness

The use of molecular techniques in respect of the rare X-linked non-syndromic form of genetic deafness demonstrates that this is a genetically heterogeneous disorder, with evidence for at least two separate gene loci on the X chromosome. Audiological heterogeneity in this condition is emphasized by the observation of both mixed deafness and sensorineural deafness in pedigrees showing evidence for linkage to Xq13-q21. The importance and shortcomings of the audiogram in assessing females who are known gene carriers is discussed.