Association of Sensory Impairment with Autism

Abstract

We read with interest A. G. Gordon’s response (Gordon, 2007, is every cause of autism a defi nite cause of deafness?) to our case report about the association of Waardenburg syndrome with intellectual disability, autistic spectrum disorder and unprovoked aggressive outburst (Kiani et al., 2007). His letter highlights an interesting link between autism and hearing impairment and offers a different perspective on the aetiology of autism. Hearing impairment and autism are both disorders of communication and can therefore be mistaken for each other during early childhood. Children eventually diagnosed with autism are often initially thought to be deaf by the parents (Grewe et al., 1994). However, both conditions may be present in a child simultaneously. Rosenhall et al., (1999) studied the presence of hearing impairment in those with a diagnosis of autism and found that 9.5% had a hearing impairment (sensorineural and/or conductive hearing loss). The prevalence of profound hearing impairment in their study was about 3.5%. Jure et al., (1991) reported a 4% prevalence of autism in 1150 children with hearing impairment. They did not fi nd any association between the severity of hearing impairment and autistic traits, but there was a relationship between the degree of intellectual disability and the autism (i.e. the higher the degree of intellectual disability, the more severe the autism). This observation is consistent with the large body of evidence showing an increased prevalence of autism and autistic traits in people with more severe intellectual disability (Deb and Prasad, 1994). The complex relationship between intellectual disability and autism is wellknown in the literature (Berney, 2000). This means that attribution of a new behavioural phenotype (including autistic traits) to a genetic syndrome (and/or a sensory impairment) alone should be made cautiously, as such an association is more probably mediated through intellectual disability (O’ Brian, 2006). The association between autism and sensory impairment is not just limited to hearing impairment. Clinicians in their day to day practice are aware of association of autism with hypo/hypersensitivity to certain sensory stimuli. A recent study (Kern et al., 2007) on sensory processing in autism shows that there are abnormalities in main sensory modalities (touch, oral, visual and auditory) and these seem to be interrelated. This supports the hypothesis that sensory dysfunction in autism is global in nature. Results of the various studies on sensory impairment and autism also show a clear association between visual impairment and increased autistic-like symptoms. However, it seems that this association has been mediated through brain damage (readers are advised to refer to Pring, 2005 for an excellent review of the subject). A well known example of this association can be seen in children with congenital rubella syndrome where Students You are en titled to a 50 % discount on a subscrip tion to The British Journal of Developm ental Disabi lities