Is an adult with Asperger syndrome sitting in your waiting room?
ABSTRACTThe prevalence of Asperger syndrome, a mild form of autism, appears to be rapidly increasing. This developmental disorder affects children and adults and can present challenges to providing medical care. In this update on Asperger syndrome, we offer guidance on how to interact with adult patients with the disorder. We also address proposed diagnostic changes scheduled to take effect in 2013.
KEY POINTS
- Indicators of Asperger syndrome include lack of eye contact, inappropriate comments, odd posture, high anxiety, and intensely focused interests.
- Asperger syndrome is evident in childhood, but it also presents undiagnosed in adulthood.
- Physicians should be aware of patients’ social differences and increased sensitivities in order to improve health care delivery.
- Episodic cognitive behavioral therapy addressing interpersonal skills can dramatically improve quality of life and independence.
- Proposed diagnostic changes scheduled to take effect in 2013 involve including Asperger syndrome as an autism spectrum disorder.
Functional magnetic resonance imaging reveals multiple differences
Functional magnetic resonance imaging (fMRI) has been used to investigate impaired social interaction, specific deficits of facial perception and recognition, sensory processing, working memory, and “theory of mind.” Hypoactivation, hyperactivation, and decreased functional connectivity have been observed depending on the mental processes evaluated.40
When undergoing facial perception tasks, subjects with autism spectrum disorders exhibit hypoactivation in the lateral aspect of the middle region of the fusiform gyrus, responsible for face identification. But they have significant activation of the limbic system, specifically the amygdala, during facial recognition. Hypoactivity in the fusiform gyrus is observed when trying to identify faces or read facial expressions.41,42 This cluster of findings helps explain misinterpretations, misidentification, and heightened affect.
A hallmark characteristic of autism is the difficulty patients have in determining intentions and interpreting others’ behavior, thoughts, or emotions. Studies of people with autism spectrum disorders show that areas often responsible for “sensitivity to others” are hypoactive.43 There is also diminished activation in the medial cingulate cortex, normally activated when these people are asked to think about themselves and who they are.44
The resting state in the brains of people with autism spectrum disorders is abnormally activated.45 They are often particularly good at attention to detail but challenged in integrating information needed for general executive functioning. Impaired sensory processing makes it difficult for them to simultaneously interpret multiple sources of sensory input.46
Perhaps some of the most exciting fMRI news comes from infant studies. Radical and axial diffusivity and fractional anisotropy techniques demonstrate differences in the brains of infants 6 to 24 months old, before symptoms of autism spectrum disorders are observed. It is hoped that early intervention could come into play before the syndrome develops fully.47
The synthesis of input of social and emotional cues is sometimes referred to in the literature as “theory of mind.” It is impaired in Asperger syndrome,48 as manifested by a lack of empathy and by challenges in perceiving others’ thoughts and feelings. The basis of impairment may be related to abnormalities in the amygdala.49 Normal awareness involves the integration of multiple neural networks in the anterior paracingulate cortex, the superior temporal sulci, and the temporal poles bilaterally, but different regions appear to be used in patients with Asperger syndrome.50 A small series of five case studies using positron emission tomography indicated that the left prefrontal cortex was the primary location for theory of mind in Asperger syndrome.51
Epilepsy, gastrointestinal problems, and sleep disturbances are associated
About 25% of people with autism spectrum disorders have epilepsy vs 2% to 3% in the general population. Asperger syndrome is associated with a much lower but still elevated risk of 4% to 6%.47,52
Gastrointestinal complaints, most often constipation or chronic diarrhea, are much more common in children with autism spectrum disorders than in the general population. Preliminary data showed that children with an autism spectrum disorder have a 42% rate of gastrointestinal problems vs 12% in unaffected siblings. There is also a correlation between the severity of gastrointestinal problems and severity of autistic symptoms.53
Research is ongoing to determine the prevalence of insomnia or interrupted sleep in those with autism spectrum disorders.54–56 Changes in sleep architecture can explain nighttime activity.
NONTRADITIONAL CONSIDERATIONS
Dietary treatment: Mixed findings
A popular hypothesis is that adherence to a gluten-free or casein-free diet can reduce symptoms of autism spectrum disorders. Preliminary reports identified several cases of children showing improvement.57 However, this has not been replicated, and more studies refute benefits of these diets.58
Essential nutritional needs should be met with any diet, whether it is designed to reduce symptoms or not. Patients with autism spectrum disorders may have strong food aversions, and dietary supplements of vitamins and minerals may be required.
Vaccines do not cause autism
Despite popular concern, recent research indicates that vaccines do not cause autism. Thimerosal, a mercury-based preservative used in childhood vaccines, was at one time implicated as a risk factor for autism spectrum disorders. The US Centers for Disease Control and Prevention (CDC) issued a precaution against using thimerosal-containing vaccines while testing was done to determine the effects on neuropsychological development.59 The CDC study as well as newer studies did not demonstrate that exposure to mercury causes these neuropsychological concerns, but researchers have continued to study the subject.60–62 The original study implicating thimerosal was disproven as scientifically unsound and fraught with conflict of interest and legal concerns. It has since been retracted, and its findings have been completely discredited.63
Other areas of research
Current research is exploring the higher prevalence of autism spectrum disorders in particular families.64–66 Autism and autism spectrum disorders may be caused by hundreds of simultaneous gene alterations or may develop as a result of reduced gene expression in two areas of the cerebral cortex where higher-order processing occurs, in the frontal and temporal lobes.67
Although genetic theories of autism predominate, a 2011 project suggests that environment is also important. A study of twins found that genetics accounted for 40% or less of cases of autism spectrum disorder, with at least 55% of cases being attributable to environmental factors.68
