Linda M. Luxon

Hospital-based universal newborn hearing screening for early detection of permanent congenital hearing loss in Lagos, Nigeria

OBJECTIVE To determine the feasibility and effectiveness of hospital-based universal newborn hearing screening programme for the early detection of permanent congenital or early-onset hearing loss (PCEHL) in Lagos, Nigeria. METHODS A cross-sectional pilot study based on a two-stage universal newborn hearing screening by non-specialist health workers using transient evoked otoacoustic emissions (TEOAE) and automated auditory brainstem-response (AABR) in an inner-city maternity hospital over a consecutive period of 40 weeks. The main outcome measures were the practicality of screening by non-specialist staff with minimal training, functionality of screening instruments in an inner-city environment, screening coverage, referral rate, return rate for diagnosis, yield of PCEHL and average age of PCEHL confirmation. RESULTS Universal hearing screening of newborns by non-specialist staff without prior audiological experience is feasible in an inner-city environment in Lagos after a training period of two-weeks. Notwithstanding excessive ambient noise within and outside the wards, it was possible to identify a test site for TEOAE screening within the hospital. The screening coverage was 98.7% (1330/1347) of all eligible newborns and the mean age of screening was 2.6 days. Forty-four babies out of the 1274 who completed the two-stage screening were referred yielding a referral rate of 3.5%. Only 16% (7/44) of babies scheduled for diagnostic evaluation returned and all were confirmed with hearing loss resulting in an incidence of 5.5 (7/1274) per 1000 live births or a programme yield of 5.3 (7/1330) per 1000. Six infants had bilateral hearing loss and the degree was severe (> or =70 dB nHL) in three infants, moderate (40 dB nHL) in one infant and mild (<40 dB nHL) in two infants. The age at diagnosis ranged from 46 days to 360 days and only two infants were diagnosed within 90 days. CONCLUSIONS Hospital-based universal hearing screening of newborns before discharge is feasible in Nigeria. Non-specialist staff are valuable in achieving a satisfactory referral rate with a two-stage screening protocol. However, a more efficient tracking and follow-up system is needed to improve the return rate for diagnosis and age of confirmation of hearing loss.

The changing face of Usher syndrome: Clinical implications

Usher syndrome is both genetically and phenotypically heterogeneous. Traditionally, the condition has been classified into three clinical types, differentiated by the severity and progression of the hearing impairment and by the presence or absence of vestibular symptoms. Recent advances in molecular genetics have enabled researchers to study the phenotypic expression in confirmed molecular groups of Usher. In response to the expansion of clinical and genetic information on Usher, we report an up to date review of the different clinical forms of Usher in known molecular groups and use the emerging evidence to appraise the diagnostic utility of the traditional classification of Usher. Our findings undermine the traditional view that the clinical types of Usher have distinct genetic causes. The pleiotropic effects of some of the major causes of Usher lead to considerable overlap between the different clinical types, with very little evidence for phenotypic-genotypic correlations. The novel synthesis emerging from this review suggests more productive approaches to the diagnosis of Usher in hearing-impaired children which would provide more accurate prognostic information to families.

Symptoms, disability and handicap in unilateral peripheral vestibular disorders. Effects of early presentation and initiation of balance exercises.

The aim of this study was to obtain a profile of disability and handicap in patients with unilateral peripheral vestibular disorders presenting to a specialist tertiary care unit. Two validated questionnaires were sent to patients who had a unilateral peripheral vestibular disorder as defined by strict criteria. Some patients still suffered moderate handicap and disability 5 years after the initial symptoms related to a unilateral vestibular disorder, although the duration of symptoms (onset to questionnaire completion) did not correlate with severity of disability and handicap, as judged by questionnaire scores. However, patients presenting to the unit within 6 months of onset of vertigo commenced balance exercises significantly earlier and had significantly lower disability scores than patients presenting later. A high proportion of non-compliance with, and delay in initiation of, vestibular rehabilitation exercises was noted in the total patient sample, while compliance with, and early initiation of, Cooksey Cawthorne exercises were significantly correlated with low disability and questionnaire scores. These findings suggest that early referral to a specialist balance unit for patients with persistent dizziness is associated with better outcome.

Screening for early childhood hearing loss in Nigeria.

Newborn hearing screening has been recognized as an essential component of public health care in early childhood in developed countries. However, such screening is yet to be widely embraced in the developing world. The new national health policy in Nigeria seeks, for the first time, to reduce the impact of permanent hearing loss on early childhood development through early detection and timely intervention services. The aim of this paper is to ascertain if newborn hearing screening satisfies the conventional criteria for a screening programme as an early detection strategy in this developing country. A review of the available literature shows that permanent childhood hearing loss is a significant health condition and its detection through screening with oto-acoustic emissions and/or auditory brainstem response is feasible in the target population. Amplification with hearing aids is an effective and preferred option for early intervention by parents. The risk of maternal anxiety from potential false-positives or the psychological cost of false assurance from false-negatives is unlikely to outweigh the benefit of screening. Newborn hearing screening is therefore a potential early detection strategy for permanent childhood hearing loss in Nigeria.

Non-hospital delivery and permanent congenital and early-onset hearing loss in a developing country.

Objective  The objective of this study was to determine the role of non‐hospital delivery and other risk factors for permanent congenital and early‐onset hearing loss (PCEHL) in a developing country.

Saccadic eye movements and anti-epileptic drugs

Saccadic eye movements can be used to evaluate different aspects of brain function, and in this article we are concerned with possible applications in relation to anti-epileptic drug treatment. Recent improvements in the technology of measurement have improved the sensitivity and objectivity of the measures. Here we review the neurophysiology of saccades, their classification, their anatomical basis and cortical control, and then published research articles concerned with the influence of anti-epileptic drugs on saccades and their parameters. It seems likely that certain anti-epileptic drugs (especially those acting on ion channels) exert their effect on saccades through ion channels, and this may have relevance to clinical and pharmacogenetic studies.

Factors associated with auditory neuropathy/dys-synchrony in a developing country

Two-stage hearing screening, with a first stage of automated otoacoustic emissions (AOAE) followed by automated auditory brainstem response (AABR), is the protocol of choice for the early detection of congenital and early-onset hearing loss (PCEHL) in a number of developed countries. However, this protocol would miss children with auditory neuropathy/auditory dys-synchrony (AN/AD). The aim of the study was to ascertain the characteristics of infants with AN/AD profile in a developing country and identify predictors of this condition in a primary care, non-hospital-based setting. Case-control analysis of the sociodemographic and medical profile of 11 infants with normal outer hair cell function, but confirmed with PCEHL, were compared to 64 infants with normal hair cell function and no PCEHL. The infants with AN/AD profile were further compared with 45 infants with PCEHL who failed transient evoked otoacoustic emissions (TEOAE). Independent predictors were determined from univariate and multiple logistic regression analyses. Factors associated with AN/AD profile in the univariate analysis were male sex (OR, 9.39: 95% CI 1.14−77.74) and hyperbilirubinaemia requiring exchange blood transfusion (OR, 5.63: CI 1.06–129.85). About 64% of the infants with AN/AD profile had a history of hyperbilirubinaemia and 54.5% were hospitalized in the first month of life for a serious illness. No independent factor was predictive of AN/AD from multiple logistic regression analysis. Infants with AN/AD profile were significantly more likely to have a history of hyperbilirubinaemia (OR, 14.00: CI 3.00−165.34) and be hospitalized in the first month of life (OR, 7.80: CI 1.80−33.77) than infants with PCEHL who failed TEOAE. There is no prognostic/selective tool for the early detection of infants with AN/AD profile in non-hospital-based settings in developing countries. AABR screening of infants with normal outer hair cells, who have a history of hyperbilirubinaemia with or without exchange blood transfusion, is recommended as far as practicable, where a two-stage TEOAE/AABR protocol is implemented.