INTELLECTUAL DISABILITY

INTELLECTUAL DISABILITY

The term intellectual disability includes impairments of general mental abilities that impact adaptive functioning. Symptoms of intellectual disability first appear during the developmental period and diagnosis requires a comprehensive assessment of intelligence across conceptual, social, and practical domains (American Psychiatric Association, 2013). Adaptive skill areas include:

·       Conceptual

·       Language

·       Reading

·       Writing

·       Math

·       Reasoning

·       Knowledge

·       Memory

·       Social

·       Empathy

·       Social judgment

·       Interpersonal communication skills

·       Ability to make and retain friendships

·       Practical/self-management

·       Personal care

·       Job responsibilities

·       Money management

·       Recreation

·       Organizing school and work tasks

Almost 10% of children with hearing loss also have intellectual disabilities. Those with an intellectual disability are at an increased risk for visual or hearing impairment or both. Detection and treatment of hearing loss in adults and children with intellectual disabilities is of utmost importance because hearing loss can exaggerate intellectual deficits by impeding the learning process. Down syndrome, also referred to as trisomy 21, is the leading cause of hearing loss and intellectual disabilities and occurs in approximately 1 in 700 births in the United States.  Audiologists are very likely to see a large number of children and adults with Down syndrome, a genetic disorder always associated with some degree of cognitive impairment. As individuals with Down syndrome age, there is a decline in intellectual ability. In fact, almost 100% of individuals with Down syndrome over 40 years of age demonstrate degenerative neuropathologic changes consistent with Alzheimer-type dementia.

Furthermore, some have speculated that the precocious aging of individuals with Down syndrome results in early presbycusis in this population. Hearing loss progresses more rapidly in adults with Down syndrome than those with other forms of intellectual disability or adults in the general population. Down syndrome is also frequently associated with conductive hearing loss and, less often, sensory/neural hearing loss. Although the majority of the conductive hearing losses in those with Down syndrome are secondary to middle ear effusion, some are the result of middle ear anomalies, such as ossicular malformations and damage to middle ear structures as a result of chronic infection. In contrast to the typically developing population, the prevalence of middle ear effusion tends to remain high in individuals with Down syndrome regardless of age. Found that adolescents with Down syndrome have poorer hearing and greater incidence of conductive hearing loss than their peers with intellectual disability, but without Down syndrome. For a comprehensive review of hearing loss associated with Down syndrome. 

Special Testing Considerations 

Little has been published on hearing assessment of adults with intellectual disability. However, it is well documented that audiologists must use test techniques that will bridge the difference between the chronologic and developmental age of individuals with cognitive disabilities to obtain valid test results. The patient’s mental or developmental age, not their chronologic age, should be considered when selecting appropriate test procedures and materials. Several investigators have evaluated the effectiveness of VRA with children having intellectual disabilities, including those with Down syndrome. With typically developing children and those with intellectual disabilities, VRA is effective with infants as young as 6 months cognitive developmental age. However, children with Down syndrome require a cognitive developmental age of 10 to 12 months to successfully participate in a VRA procedure. Furthermore, behavioral thresholds of infants with Down syndrome have been found to be 10 to 25 dB poorer than those of typically developing infants when all had normal hearing verified via ABR. This elevation of behavioural thresholds is presumed to be the result of more inattentive behavior on the part of the children with Down syndrome relative to their typically developing peers. Moreover, this inattentive behavior provides additional reason to utilize a test battery that includes physiological measures when testing children with Down syndrome. Although it is recommended that audiologists attempt to elicit a spontaneous head-turn response during the VRA conditioning process, some children with intellectual disability may not have developed auditory localization ability. Recall that auditory localization is a higher order skill than detection, the required skill for VRA. In such cases, several administrations of paired conditioning trials may be required. If the patient does not respond to the auditory stimuli, the audiologist may be left with the question, “Does the patient not hear the stimuli, or can she or he not perform the task?” One method that can answer this question is for the audiologist to place the bone vibrator either in the patient’s hand or on the head and, using a low-frequency stimulus at approximately 50 to 60 dB hearing level (HL), determine if the patient can perform the task using this vibrotactile cue. In this way, the patient is able to feel the stimulus and, thus, is not required to hear to participate. If the patient is able to cooperate for the task under these vibrotactile conditions, then the audiologist should return to the auditory stimuli and continue testing with the knowledge that the patient understands the task. If using a play audiometric technique, it is often appropriate for the audiologist to demonstrate the play task to the patient with intellectual disability rather than attempting to explain the instructions verbally. Because learning the desired response behaviors may take longer for children and adults with intellectual disability, it may be useful to have them practice the listening task at home before coming to the clinic.