AUTISM SPECTRUM DISORDER

AUTISM SPECTRUM DISORDER

Autism spectrum disorder (ASD) is a developmental disorder characterized by symptoms appearing in early childhood and impairing day-to-day life function. These symptoms include qualitative impairments in social/communication interaction and repetitive and restricted behaviors, according to the Diagnostic and Statistics Manual of Mental Disorders. Under the umbrella of ASD, a patient’s symptoms will fall on a continuum, with some showing mild symptoms and others, more severe. A diagnosis under the general diagnostic category of ASD is relatively new. Prior to the publication of DSM-5, there were five ASDs, each of which had a unique diagnosis: classic autism, pervasive developmental disorder (PDD), Asperger’s disorder, Rett’s syndrome, and childhood disintegrative disorder. With the exception of Rett’s syndrome, these disorders are now subsumed into the diagnosis of ASD. Rett’s syndrome is now its own entity and is no longer a part of the autism spectrum.

ASD is thought to have an early onset, with symptoms appearing before 24 months of age in most cases. Although a definitive diagnosis of autism is not generally made until the age of 3 years or later (Mandell et al., 2005), there are a growing number of reports of stable diagnoses following identification as young as 2 years (Chawarska et al., 2009). Prevalence estimates of ASD have increased steadily over time from reports of 1 to 5 children per 10,000 in the 1970s. Current numbers from the Centers for Disease Control and Prevention suggest a prevalence of 114 per 10,000 children (Baio, 2012; Rice, 2009). It remains to be seen whether there has been a true increase in prevalence of ASD over time or the reported changes in prevalence can be explained by changes in diagnostic criteria and increased awareness of the disorder by parents and professionals. Boys are more likely to be affected with autism than girls, at a ratio of more than 3:1. About 50% to 70% of children with ASD also have an intellectual disability.

There is no strong evidence to suggest that individuals with ASD have a greater risk of hearing loss than the general population. However, the presence of unusual sensory responses, including abnormal responses to sound, is considered an associated feature of ASD. For example, individuals with ASD might completely ignore sounds that would result in a reaction from typically developing individuals. Other times, they often appear to be overly sensitive to sound by covering their ears with their hands when loud or unexpected sounds occur. In addition to these abnormal responses to sound, young children with ASD are known to lag behind on language milestones. Therefore, those with ASD will likely be referred to audiologists for hearing assessments as part of the developmental evaluation to rule out hearing loss as the cause of language delay. On average, behavioral responses to sound of children with ASD who have normal hearing are elevated and less reliable relative to those of typically developing children. Relatively little is known about higher order auditory abilities of individuals with ASD. However, altered temporal processing has been recorded in both adults and children with ASD.

Special Testing Considerations

Children with ASD who have hearing loss are diagnosed, on average, almost 1 year later than those without hearing loss. Therefore, it is reasonable for audiologists to be alert to the general behavioral characteristics of childhood ASD to facilitate referral for evaluation when indicated. Several screening tools are available that can be used by audiologists. These include, among others, the Modified Checklist for Autism in Toddlers (M-CHAT) and the Pervasive Developmental Disorder Screening Test II (PDDST-II).

Understanding the general behavioral characteristics of those with ASD can also be helpful to audiologists as they consider modifications to the traditional test battery. Because the majority of those with ASD exhibit cognitive deficits, behavioural abnormalities, and hypersensitivity to sensory stimulation, audiologists should be prepared to address those issues during the test session. For instance, transitions are often difficult for individuals with ASD. When possible, audiologists should avoid travel from room to room with the patient, taking care to escort the patient to the testing area immediately rather than keeping him or her in the waiting area.

Regardless of the chronologic age of the individuals, audiologists will need to use behavioral test procedures that are appropriate for their patient’s cognitive level. This may mean that procedures typically used with infants and young children such as visual reinforcement audiometry (VRA) or play audiometric techniques will be used with older children or even adults. If VRA is used, one should consider minimizing the impact of the reinforcement by turning off the animation (if a lighted, animated toy is used) or using a video reinforcement. Other testing options for patients functioning at a developmental level of 2.5 years or greater are conditioned play audiometry (CPA) and tangible-reinforcement operant conditioning audiometry (TROCA). TROCA is often used in pediatric practices that specialize in serving those with multiple disabilities. TROCA requires the patient to press a bar or a button whenever a sound is heard, which is paired with the dispensing of a tangible reinforcement (e.g., small piece of food). TROCA is noted to be particularly effective with children having cognitive or behavioral (e.g., ASD) disorders. A significant number of children with ASD receive other clinical services (e.g., speech therapy).

Patients with ASD are often resistant to earphones or probes used for individual ear testing. Audiologists can ask the parent or caregiver to practice listening activities with headphones with the patient prior to the appointment. If a patient with ASD will not allow the placement of earphones or probes, audiologists might have to resort to sedated procedures. This is certainly true if one plans to fit hearing aids. Individuals with ASD are known to be difficult to sedate with currently available pediatric sedating agents and are at risk for seizures while under sedation. Therefore, consultation with the physician in charge of administering and monitoring the sedation process will need to include notification of the patient’s diagnosis of ASD.