Tourette Disorder and Other Tic Disorders

Clinical Description

There are four tic disorders described in the Diagnostic and Statistical Manual (DSM-IV-TR): 1) Tourette disorder (also known as Tourette syndrome or TS); 2) chronic motor or vocal tic disorder; 3) transient tic disorder; and 4) tic disorder not otherwise specified. Tourette disorder (which will be referred to as TS) is an inherited neurological disorder with onset in childhood, characterized by the presence of multiple motor tics and at least one phonic (vocal) tic. The tics characteristically wax and wane. TS was once considered a rare and bizarre syndrome, with a psychogenic cause. The eponym for the disorder was bestowed by Jean-Martin Charcot on behalf of his resident, Georges Gilles de la Tourette, a French neurologist who published an account of nine patients with the unusual movement disorder in 1885.

For chronic motor or vocal tic disorder, there are single or multiple motor or vocal tics, but not both. Transient tic disorder is single or multiple motor and/or vocal tics for no
more than 12 consecutive months. For all of the tic disorders, the tics must occur many times a day, nearly every day, and there must never be a tic-free period of more than three consecutive months. The disturbance must cause distress and impairment and have an onset before the age of 18.

Epidemiology

Estimates of the disorder have increased over time, with the ascertainment of milder forms of tics. It is estimated that 1–10 per 1,000 children suffer from a diagnosable tic disorder. A large, community-based study suggested that over 19% of school-aged children have had tics of some type, with almost 4% of children in regular education fulfilling the diagnostic criteria for TS. As many as 1 in 100 people may experience some form of tic disorder, which includes transient tics, chronic tics, or TS. Males are affected three to four times more often than females. This number decreases in adulthood, as the tic symptoms frequently resolve in the milder forms of the disorder.

Tip

Children with TS describe “premonitory sensory phenomena” or a vague, although sometimes powerful, feeling of needing to tic. Some children liken the feeling to the “need to sneeze” or to “scratch an itch.” They are able to suppress the urge for a period of time, but the need to tic seems to build up as irresistible tension. Performing the tic tends to relieve the tension, at least for a time. High levels of either positive or negative emotions tend to exacerbate tics. Concentration in an absorbing activity often leads to a decrease in tics. There are surgeons with TS. They are able to suppress tics for long periods of time for very complex procedures.

Etiology

Genetic studies have proven that the overwhelming majority of cases of TS are inherited. Recent research suggests that a small number of TS cases may be caused by a defect on chromosome 13 of gene SLITRK1. TS is most likely the result of an additive model involving multiple genes in most affected individuals.

The inherited vulnerability to tic disorders may produce varying symptoms in different family members. A person with TS has about a 50% chance of passing the genes to one of his or her children. The genes may express as TS, as a milder tic disorder, or as obsessive-compulsive symptoms with no tics at all. Boys are more likely to demonstrate tics, and females are more likely to demonstrate obsessive-compulsive (OCD) symptoms. Only a minority of the children who inherit the genes will have symptoms severe enough to require medical attention.

While a genetic mechanism is clear, for at least some children with the disorder the exact mechanism has not been established. Research presents considerable evidence that abnormal activity of the brain neurotransmitter, dopamine is involved. Neuroanatomic models implicate abnormalities in the complex cycling cascade of dopaminergic neuronal functions and influences between the brain’s cortex and subcortex (especially the striatum and thalamus).

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