Neonatal hearing screening in Benin City

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Abstract

Objective

Congenital hearing loss is a major health care problem that tends to retard the developmental milestones of children. It takes early detection and intervention to avoid a permanent loss in acquisition of speech and cognitive functions. Hence, the importance of hearing screening in all newborns especially in the developing world for accurate statistics and early intervention. Therefore, this work was aimed at detecting the crude prevalence of congenital hearing loss among the newborns in Benin City.

Methodology

Consecutive neonates at designated immunization centers in Benin City metropolis were screened for hearing loss via the detection and analysis of distortion product otoacoustic emissions from both ears. The handheld otoacoustic machine model MAICO 8172 was employed and the outcome results presented in tables. Statistical analysis was performed using SPSS 11.

Results

A total of 400 neonates (218 males and 182 females) were screened for the presence of otoacoustic emission in both ears. Ninety neonates (22.5%) p < 0.05 were referred. Bilateral hearing loss was seen in 26 (6.5%) whereas 64 (16%) had unilateral loss.

Conclusions

The screening tests suggest a high crude prevalence (6.5%) of bilateral neonatal hearing impairment in Benin City necessitating confirmation and intervention. The study fortifies the need for hearing screening among all new born in developing countries.

Introduction

Congenital hearing loss is a major abnormality that threatens the adequate development of a child. Adequate hearing within the first year of life is critical in the development of speech and cognitive functions of infants. Beyond this period, neural plasticity sets in [1]. Neonatal hearing loss often goes undetected as hearing loss is a hidden disability. As many as 126,000–500,000 babies are affected yearly, 90% of which live in developing countries [2]. A study at Otorhinolaryngology Department of the University College Hospital Ibadan Nigeria revealed that sensorineural hearing loss accounted for about 14.5% of all the pediatric cases seen within the period [3]. This is why a reliable screening method for early detection of hearing loss in all newborns is necessary.

Screening has been defined as the systematic application of a test or enquiry, to identify individuals at sufficient risk to benefit from further investigation or direct preventive action, amongst persons who have not sought medical attention on account of symptoms of that disorder [4].

Studies have shown that children with hearing impairment do not attain the same level of speech, language and psycho-social development as their normal hearing peers [5], [6].

Currently, universal newborn hearing screening is being promoted in developed countries as an early detection strategy for hearing loss [7].

Children not screened at birth may have delayed diagnosis of hearing loss for as long as 3 years [8].

Following the adoption of universal newborn hearing screening, diagnosis of hearing loss can be made as early as at the mean age of 3.5 months [9].

Treatment of hearing loss has been shown to improve the acquisition of communication skills [10]. It becomes imperative to detect hearing loss early in the life of the child so that early intervention can be instituted. This is the basis of the Universal newborn hearing screening (UNHS) which advocates for the screening of all newborns for hearing loss on discharge from the delivery hospital or before one month of age and to ensure that babies who do not pass the test have a follow-up evaluation before three months of life and to ensure that babies who are detected to be deaf or hard-of hearing receive interventional services before the age of 6 months [11].

The introduction of electrophysiologic methods of screening for hearing loss with the measurement of otoacoustic emissions and auditory brainstem response has made this possible with many countries in the developed world already doing routine screening of all newborns.

Otoacoustic emissions are defined as the audio frequency energy which originates in the cochlea and is released from the cochlea, transmitted through the ossicular chain and tympanic membrane and measured in external auditory canal. They were first reported by Kemp in 1978 [12].

They can occur spontaneously or in response to acoustic stimuli. Otoacoustic emissions are believed to reflect the active biomechanical movement of the basilar membrane of the cochlea. Distortion product otoacoustic emissions are generated in response to two tones of different frequencies presented simultaneously. The interaction of the 2 tones within the normal cochlea gives rise to an audible signal at a specific additional frequency. This is referred to as the Distortion product. This signal is recordable at the external auditory canal by means of a microphone embedded in the probe. Regrettably, these screening tests are not readily available in the developing world thus hampering the possibility of a universal screening test among the newborns.

Section snippets

Methodology

This is a prospective cross-sectional study conducted from February 2007 to April 2007 at immunization clinics of the University of Benin Teaching Hospital Benin City, Central Hospital, Faith Mediplex, and 3 other private clinics providing immunization services within the metropolis over a 3 month period. Ethical clearance was obtained from the hospital's ethics committee. Informed consent was also obtained from the parents/care givers.

The subjects were consecutive neonates brought for the BCG

Results

A total of 400 neonates were screened. There were 218 (54.5%) males and 182 (45.5%) females (Table 1). The age ranged between 1 and 28 days of life with a mean age of 10.55 days. A total of 800 ears were examined during the period of the study. Of the 800 ears screened for the presence of OAEs, 116 (14.5%) did not have emissions. A total of 26 (6.5%) neonates failed the screening test in both ears while 64 (16%) failed the screening test in only one ear (Table 2). Of those failing the test in

Discussion

Hearing loss is a disability that is usually hidden and does not generate as much sympathy as other more obvious disabilities. Hearing loss may be graded as mild, moderate, severe or profound. It may be unilateral or bilateral. Severe or bilateral hearing loss enjoys earlier detection than mild or unilateral hearing loss. Parents are often the first to suspect the existence of a hearing impairment as a result of inattention or erratic responses to sounds or delay in speech development by the

Conclusions

The screening tests suggest a high crude prevalence (6.5%) of bilateral neonatal hearing impairment in Benin City necessitating confirmation and intervention. There is an urgent need for the institution of universal screening for hearing loss in all newborns as early detection will facilitate prompt intervention thereby ensuring adequate development of language and other cognitive functions.

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