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F O Duffy, D Mc Askill, I J Keogh
Irish Medical Journal
Children with Downs Syndrome: Are we Hearing their needs?
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Downs Syndrome, Hearing
                           Introduction Down’s syndrome (DS) affects 1 in every 732 live births and is the most common cause of intellectual impairment affecting children (1). This increases to 1 in every 84 births when maternal age exceeds 40 (2).  It is a genetic disorder, caused by the presence of trisomy of chromosome 21st. Children with Down’s syndrome are at risk of a multitude of health related problems such as visual difficulties, congenital heart disease, thyroid disease, obstructive sleep apnoea and immunodeficiency (3, 4). Crainofacial features such as cleft or high-arched palate, hypoplastic maxilla and narrow external auditory canal are often found in Down's syndrome, as well as hypodontia or anodontia (5).  The most common health problem experienced in Down’s syndrome is hearing loss. At least 75% of children are affected along a mild to profound spectrum of hearing loss (6).  Although there is considerable variation most individuals with DS have speech and language deficits particularly in language production, syntax and speech intelligibility (7). Optimising hearing is essential to minimise speech and cognitive delay.   The main cause of conductive hearing loss is persistent otitis media with effusion (OME); Park et al reported the incidence of conductive hearing loss at 37.9% of DS patents (8). In the general population up to 80% of children are reported as having at least one episode of OME by age four (9). The most effective management of OME is still contentious (10). In non syndromic children 70-80% will resolve without intervention within 3-4 months (11). Down’s syndrome children with almost universally get OME, the etiology of which is secondary to both anatomical and physiological dysfunction. Anatomical factors including mid face hypoplasia, contracted nasopharynx, abnormal shape in the Eustachian tube and poor function of the tensor veli muscle responsible for opening and closing the Eustachian tube. Poor physiological function of the immune system also predisposes to recurrent OME.  Otitis media with effusion occurs at a younger age and persists to an older age than in other children (12). Sensory neural hearing loss is also relatively high in DS with up to 5% being affected (13).    Other otological disorders occurring at higher frequency in DS include wax impaction, tympanic membrane retraction, auditory canal stenosis and poor mastoid pneumatization (14). Inner ear abnormalities are also common in Downs Syndrome.  A study of fifty nine patients by Blaser et al found universally hypoplastic inner ear structures with vestibular malformations particularly common (15). Downs syndrome children require special consideration and early intervention to avert the secondary handicap caused by hearing loss.
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