It seems like not a day in the pediatric clinic goes by without at least one child with autism spectrum disorder (ASD) on the schedule. Prevalence estimates for the condition are on the rise, perhaps as a result of greater awareness and broadening definitions of the disorder. Current figures from Australia, the United States, and Europe suggest that approximately one in 90 to 100 children are affected, making ASD one of the most common causes of educational vulnerability in children.
According to the American Psychiatric Association, autism spectrum disorder is a neurodevelopmental condition characterized by 1) deficits in social communication and social interaction and 2) restricted repetitive behavior, interests, and activities.
One of the clinically pervasive features of autism spectrum disorders is abnormal response to sensory stimuli. This feature can be seen across multiple modalities, including the visual, where fixation on light sources, linear patterns, and peripheral objects is common, and the somatosensory, where children may show aversion to light tactile stimuli and difficulties with variations in food textures.
Unusual responses to auditory signals are also particularly prevalent. Every experienced pediatric clinician will have seen children with ASD who have hypersensitivity or hyposensitivity to sound. For children in the former category, sounds at everyday levels may be distressing.
Among those in the latter group, reduced responsiveness, particularly in the presence of background noise, can exacerbate social and communication difficulties and threaten educational progress. A recent report suggests, in fact, that the most significant predictor of educational performance in children with ASD is their ability to understand speech, perform auditory tasks, and maintain concentration in the presence of background noise (Am J Occup Ther 2008;62:564-573).
A MATTER OF TIMING CUES
Why children with ASD have auditory figure/ground problems is yet to be fully determined. Coexisting disabilities such as attention deficits, language disorders, and intellectual and learning disabilities, which are all relatively common in autism spectrum disorders, are likely to exhert an influence.
Another limiting factor may be the way in which acoustic stimuli are represented in the central auditory pathways. Evoked potential investigations have shown neural conduction abnormalities extending from the brain stem through to cortical levels, and recent psychophysical and speech perception studies have suggested that listeners with ASD have specific processing deficits that affect their perception of timing cues.
This auditory temporal disruption may be particularly important for functional hearing, as it affects the ability to use the brief, relatively quiet periods that occur in environmental noise to access the speech signal. Whatever the reasons, understanding speech in background noise is a particular problem, and ASD listeners have consistently shown higher reception thresholds in open-set testing than their typically developing peers.
KEEPING DOWN THE NOISE
Management of speech-in-noise deficits has been a clinical concern among audiologists for decades but has become an area of vigorous research only in recent years. There are basically two approaches to minimizing the educational risk to affected children. The first is to improve the quality of the signal reaching the child's ear, and the second is to train the child to make the best use of that signal.
In the case of the latter method, no results of training programs for children with autism spectrum disorders have been reported, but there is a growing literature suggesting that speech perception in children (and adults) with figure/ground problems can be significantly improved through targeted auditory habilitation (Audiol Res 2012;2[e15]:86-93; Cereb Cortex 2012;22:1180-1190; Proc Natl Acad Sci U S A 2013;110:4357-4362).
Improvement of the classroom listening environment can be achieved through structural modifications, such as fitting of ceiling tiles and installation of carpeting, and through sound-field amplification of the teacher's voice with a loudspeaker. These approaches have the advantage of improving the listening conditions for every child in the room, but they are especially beneficial for those with figure/ground problems.
Personal frequency modulation (FM) listening systems are another option. These devices are routinely fit to children with sensorineural hearing loss, with well-accepted benefits for perception in structured listening situations. Furthermore, FM systems have been shown to assist children with auditory processing deficits (Int J Audiol 2009;48:371-383) and individuals with speech-in-noise problems due to auditory neuropathy (Neuroscience 2010;171:552-555).
The provision of this technology seems an obvious choice for children with ASD, but clinical trials in this population are lacking, perhaps because of concerns about device tolerance in children who have intellectual impairment and/or tactile hypersensitivity. A recent study by Schafer et al has, however, presented some promising FM system results for a cohort of elementary school-age children with ASD.
Personal FM Systems for Children with Autism Spectrum Disorders (ASD) and/or Attention-Deficit Hyperactivity Disorder (ADHD): An Initial Investigation
Schafer EC, Mathews L, et al J Commun Disord 2013;46(1):30-52
This article describes a trial of FM listening devices in a group of seven children with ASD who were 9- to 11-years-old at assessment. All were relatively high functioning, meaning that they could speak, understand directions, and comply with examiner requests. An additional four participants with attention-deficit hyperactivity disorder (ADHD) who were 10- to 12-years-old at assessment also were included. For the most part, the authors pooled the ASD and ADHD findings, arguing that children in both groups exhibit similar patterns of abnormal listening behaviour.
Each child underwent a highly structured FM system trial within a special classroom setting for children with learning difficulties. Participants wore bilateral FM receivers for one 45-minute session of teacher-focused activity per day across a five-week study period. Listening and classroom performance were evaluated through formal measures of speech recognition, observation of classroom behavior, and teacher-rated scales.
Overall, the study findings were encouraging. Most subjects were prepared to wear the device consistently, which is not a given in this subject group, and nine of the 11 participated in the trial through to completion.
Speech reception thresholds in the unaided condition were depressed, confirming the figure/ground deficit in this group, but improved significantly when FM aided, reaching levels expected for typically developing children. Furthermore, classroom behavior improved, with participants spending a higher proportion of time on task and teachers reporting enhanced listening when children were wearing the device.
INTERPRET WITH CAUTION
This study offers a glimpse of the potential benefits of FM fitting in children with ASD. The work does, however, have some limitations, and the findings need to be interpreted with caution.
For example, the trial was carried out in an ideal educational setting, with a small class size (14 students) and teachers attuned to the needs of children with learning impairment. Implementing assistive listening strategies in mainstream classrooms is never straightforward, and achieving and maintaining compliance among ASD children is likely to be more challenging in that environment.
Also, the participants in this study were all high-functioning children with relatively few behavioral issues. It could be argued that youngsters at the other end of the disability spectrum would have an even greater need for better hearing, but expecting these kids to tolerate any device, even for a short period of time, may be unrealistic.
Finally, the trials in this study were strictly controlled and relatively brief. It may be that a discrete period of aided listening each day is beneficial for the child (and teacher), but, if we believe that FM systems can alleviate the educational difficulties faced by children with ASD, the goal should surely be to have them wear the devices for longer time periods and in a broader range of communication situations.
It remains to be seen if this goal can be achieved, but one encouraging sign from the current study was that all but one of the children who completed the trial were keen to continue wearing their FM systems.
The clear message in the data provided by Schafer et al is that improving the classroom signal-to-noise ratio can significantly enhance listening, attention, and communicative behavior in children with autism spectrum disorders, as it does for typically developing kids. How these outcomes are best achieved in individual children likely will vary, but personal FM systems appear to be an option worth considering in at least some children with ASD.
References on Tap
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