Neuropsychological function in Tourette syndrome.

The accumulated body of scientific evidence regarding intellectual function, presence of learning disorders, and specific neuropsychological deficits in TS suggests that difficulties in these areas are present in a significant percentage of patients with TS. Despite the numerous methodological shortcomings of past neuropsychological studies of TS, relatively robust and consistent findings have emerged. The literature to date has suggested that intellectual ability is normally distributed in TS. Whether or not individuals with TS have significant discrepancies between their verbal and nonverbal abilities remains unclear. The prevalence of learning disabilities in TS has been reported to be similar to the base rates reported for the general population, although there is evidence to suggest that the prevalence of LDs in children with TS may actually be lower and specific for difficulties in math and written language. Specific cognitive deficits in TS consist of visuomotor integration problems, impaired fine motor skill, and executive dysfunction. The presence of comorbid conditions, notably ADHD and OCD, appears to significantly increase the likelihood that an individual with TS will also have learning problems or some demonstrable cognitive impairment. The presence of a learning disability, specific academic deficiency, or cognitive deficit may pose a greater obstacle for persons with TS than the tic disorder itself. This is particularly salient for children with TS, who may be at a higher risk for poor school performance and academic failure. The psychosocial impact of these problems is also far-reaching. Given the recent emphasis on the early detection of academic and learning problems, it would seem prudent that children with TS who are suspected of having neuropsychological difficulties be evaluated as soon as possible. There are numerous educational interventions and accommodations available to children with LDs and/or specific academic weaknesses that can work equally well in children with TS. The available body of scientific evidence suggests that persons with TS have normally distributed intellectual ability. This would suggest a diminished role for routine IQ testing unless there is compelling clinical evidence to suggest that the IQ score be obtained, such as when the individual is suspected of having an LD. Given that children with TS may be particularly at risk for learning disabilities or academic deficiencies in math and written language, a complete psychoeducational workup should be conducted on any child with TS who is suspected of having such difficulties. This evaluation should be conducted as early as possible, so that educational interventions can be implemented. Traditionally, the psychoeducational evaluation is performed by the school psychologist and should include standardized IQ assessment and academic achievement testing that can objectively identify and quantify the nature and severity of the learning problem. Once the problem has been documented, the school psychologist should recommend appropriate educational and remedial interventions. In addition to psychoeducational testing, neuropsychological testing is indicated to identify specific cognitive deficits that might be present in children with TS, notably problems with visuomotor integration, motor skill, and executive function. The psychoeducational evaluation performed by the school psychologist typically does not assess these cognitive functions. Therefore, referral for neuropsychological testing is indicated if there is a strong clinical suspicion of cognitive deficits. The accumulated neuropsychological literature in TS suggests that a broad-based, comprehensive, and lengthy neuropsychological examination is not necessary, however. At a minimum, the neuropsychological test battery should include assessment of visuomotor integration ability, motor skills, spatial/perceptual abilities, and executive function. This type of assessment would take less time to complete and has greater sensitivity and specificity for identifying neurocognitive deficits that are believed to be unique to TS. Neuropsychological functioning continues to be an important component in understanding the full neurobehavioral spectrum of TS. At present, there is great opportunity to explore neuropsychological functioning in TS with newly emerging technology such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and related techniques that assess cortical metabolic activity, as well as newer electrophysiological techniques. This technology, notably fMRI, allows investigation of neuropsychological functioning in vivo and may reveal important clues to the neuroanatomic substrates of neuropsychological impairment of learning disabilities in TS.