Asperger Syndrome Workup

Updated: Mar 26, 2014
  • Author: James Robert Brasic, MD, MPH; Chief Editor: Caroly Pataki, MD  more...
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Workup

Approach Considerations

Neuropsychological testing can be used to uncover characteristics of Asperger syndrome. Audiography is indicated to rule out auditory discrimination deficits. Magnetic resonance imaging (MRI) and positron emission tomography (PET) can reveal brain anomalies associated with the condition. Event-related brain potential testing with electroencephalography (EEG) may demonstrate errors in cortical auditory discrimination. Genetic testing may be helpful.

A neurologist should be consulted for examination and neuropsychological testing. Neuropsychological assessments should focus on simple and complex problem-solving tasks, using tests and scales such as the following:

  • Wisconsin Card Sorting Test
  • Trail-Making Test
  • Stanford-Binet Scale

Such diagnostic measures can demonstrate marked deficits in verbal and nonverbal functioning and intelligence level.

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Magnetic Resonance Imaging

Although MRI is not required for diagnosing Asperger syndrome, it can be helpful for identifying cortical defects in the right-central perisylvian area and incomplete formation of the posterior-inferior frontal gyrus (ie, pars opercularis and pars triangularis). However, the results of MRI are inconsistent.

MRI may demonstrate the following:

  • Hypoplasia of the inferior precentral gyrus and the anterior portion of the superior temporal gyrus, resulting in a widening of the sylvian fissure and a partial exposure of the insular cortex
  • Hypoplasia of the right temporo-occipital cortex
  • Small gyri of the posterior parietal lobes
  • Enlargement of the right lateral ventricle
  • Diminished size of the midbrain and medulla oblongata

Functional MRI demonstrates that exposure to facial expressions of fear, disgust, happiness, and sadness yields less activation of the fusiform and extrastriate cortices in people with Asperger syndrome than in healthy, normal control subjects. [42] In response to fearful faces, people with Asperger syndrome demonstrate greater activation in the anterior cingulate gyrus and the superior temporal cortex, whereas control subjects demonstrate greater activation in the left amygdala and the left orbitofrontal cortex. [43]

Herrington et al reported less activity in the inferior, middle, and superior temporal regions in people with Asperger syndrome in response to a task typically interpreted as human movement. [44]

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Positron Emission Tomography

Like MRI, PET is not required for diagnosing Asperger syndrome. In some individuals, PET reveals multiple deficits. On scanning with 2-deoxy-2-F-18-fluoro-D-glucose, the anterior rectal gyrus of some people with Asperger syndrome is larger on the left than on the right—the opposite of the asymmetry seen in most people. Other patients exhibit an increased glucose metabolic rate in the right posterior calcarine cortex and a decreased glucose metabolic rate in the left posterior putamen and left medial thalamus. (See PET Scanning in Autism Spectrum Disorders.)

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Event-Related Brain Potential Testing

Although not required for diagnosis, event-related brain potential testing (ie, electroencephalographic [EEG] measurement of brain responses to specific sensory, cognitive, or motor events) has identified errors in cortical auditory discrimination in people with Asperger syndrome. Mismatch negativity in event-related brain potentials demonstrates how well a person determines changes in sounds against the other sounds of the environment. People with Asperger syndrome are hypersensitive to changes in sounds. [13, 45]

Behaviorally, people with Asperger syndrome have been shown to process faces differently, and event-related potential studies have demonstrated this difference at a neurologic level. O'Connor et al found that in comparison with healthy control subjects, people with Asperger syndrome are slower to recognize faces. [46]

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Computed Tomography

Computed tomography (CT) of the head cannot be used either to diagnose or to rule out Asperger syndrome, because no consistent CT findings are evident in people with this condition. Nevertheless, CT can be valuable for excluding treatable conditions in the differential diagnosis, such as neurologic disorders (eg, tumors). Analysis of head CT scans inconsistently reveals enlargement of the third ventricle and diminution of the caudate nucleus.

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Genetic Testing

Patients with autism spectrum disorder (ASD), intellectual disability, or both may benefit from chromosomal microarray (CMA), or array comparative genomic hybridization (aCGH), testing to look for duplication or deletion of genomic material (otherwise known as copy number variants [CNVs] or genomic dosage anomalies). [47] Genetic testing is more likely to yield results if the patient has dysmorphic features or has a family history of fragile X syndrome.

Depending on the patient's clinical presentation, other recommended genetic tests may include any of the following:

  • Karyotyping
  • Fragile X ( FMR1 molecular studies)
  • Methylation studies
  • Methyl-CpG-binding protein (MECP2) analysis [5]
  • Phosphatase and tensin (PTEN) homolog testing [6]
  • Specific gene sequencing when a particular syndrome is suspected

Advances in genetic testing have resulted in the development of next-generation sequencing panels that allow simultaneous analysis of as many as 62 genes associated with genetic syndromes that have autism or autistic features as part of their clinical profile. However, although microarray testing has provided many families with diagnoses, it cannot detect single point mutations in a gene.

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