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Tourette Syndrome: Causes and Underlying Mechanisms

Although Tourette syndrome (TS) is clearly influenced by genetic factors, immunological, infectious, and environmental mechanisms are also implicated and/or suspected. Whether co-morbid disorders, such as ADHD and OCD, are distinct from TS or are part of the TS spectrum is unknown. Some have hypothesized that TS may manifest as a tic disorder in some children, but as obsessions and compulsions in others. [Como: 2005]
TS is thought to be inherited in an autosomal dominant fashion with incomplete penetrance; however, newer models that propose multiple gene and epigenetic contributions might be more correct. What is known from incidence data are that more males than females exhibit TS, and that children of one or both parents with TS may have between a 25 - 50% chance of also exhibiting tic disorders. [McMahon: 2003] Within an affected family, symptoms can range.
Immunological factors have been implicated due to the overlap of some children having TS with possible Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS). [Trifiletti: 1999] [McMahon: 2002] PANDAS remains controversial [King: 2006] with conflicting research findings, though several studies are supportive, such as one study demonstrating antibodies against neurons in the basal ganglia in most cases of Sydenham chorea and approximately 60% of those with TS. [Church: 2003] As such, a broader concept, referred to as CANS (Childhood Acute Neuropsychiatric Symptoms) has been proposed. [Singer: 2012]
There are many lines of evidence that link TS with pathways between the prefrontal cortex, the thalamus, and the basal ganglia and changes in the distribution and activity of the neurotransmitter dopamine. For example, medications that decrease tics are known to alter traffic through these pathways (e.g., the antipsychotics haldoperidol and pimozide), and data from functional imaging [Butler: 2006] of individuals with TS support these neurophysiological mechanisms. Finally, deep brain stimulation to specific suspected brain regions appears helpful in some people with refractory TS. [Bajwa: 2007]

Authors

Authors: Samuel H. Zinner, MD - 9/2013
Lynne M Kerr, MD, Ph.D. - 9/2013

Page Bibliography

Bajwa RJ, de Lotbinière AJ, King RA, Jabbari B, Quatrano S, Kunze K, Scahill L, Leckman JF.
Deep brain stimulation in Tourette's syndrome.
Mov Disord. 2007;22(9):1346-50. PubMed abstract

Butler T, Stern E, Silbersweig D.
Functional neuroimaging of Tourette syndrome: advances and future directions.
Adv Neurol. 2006;99:115-29. PubMed abstract

Church AJ, Dale RC, Lees AJ, Giovannoni G, Robertson MM.
Tourette's syndrome: a cross sectional study to examine the PANDAS hypothesis.
J Neurol Neurosurg Psychiatry. 2003;74(5):602-7. PubMed abstract / Full Text

Como PG, LaMarsh J, O'Brien KA.
Obsessive-compulsive disorder in Tourette's syndrome.
Adv Neurol. 2005;96:249-61. PubMed abstract

King RA.
PANDAS: to treat or not to treat?.
Adv Neurol. 2006;99:179-83. PubMed abstract

McMahon WM, Carter AS, Fredine N, Pauls DL.
Children at familial risk for Tourette's disorder: Child and parent diagnoses.
Am J Med Genet B Neuropsychiatr Genet. 2003;121(1):105-11. PubMed abstract

McMahon WM, Filloux FM, Ashworth JC, Jensen J.
Movement disorders in children and adolescents.
Neurol Clin. 2002;20(4):1101-24, vii-viii. PubMed abstract

Singer HS, Gilbert DL, Wolf DS, Mink JW, Kurlan R.
Moving from PANDAS to CANS.
J Pediatr. 2012;160(5):725-31. PubMed abstract

Trifiletti RR, Packard AM.
Immune mechanisms in pediatric neuropsychiatric disorders. Tourette's syndrome, OCD, and PANDAS.
Child Adolesc Psychiatr Clin N Am. 1999;8(4):767-75. PubMed abstract