Tourette's was once considered a rare and bizarre syndrome, most often associated with the exclamation of obscene words or socially inappropriate and derogatory remarks (coprolalia). However, this symptom is present in only a small minority of people with Tourette's.Tourette's is no longer considered a rare condition, but it may not always be correctly identified because most cases are classified as mild. Between 1 and 11 children per 1,000 have Tourette's; as many as 10 per 1,000 people may have tic disorders,with the more common tics of eye blinking, coughing, throat clearing, sniffing, and facial movements. People with Tourette's have normal life expectancy and intelligence. The severity of the tics decreases for most children as they pass through adolescence, and extreme Tourette's in adulthood is a rarity. Notable individuals with Tourette's are found in all walks of life.
Causes
The exact cause of Tourette's is unknown, but it is well established that both
genetic and environmental factors are involved.Genetic studies have shown that
the overwhelming majority of cases of Tourette's are inherited, although the
exact mode of inheritance is not yet known,and no gene has been identified.[In
some cases, tics may not be inherited; these cases are identified as "sporadic"
Tourette syndrome (also known as tourettism) because a genetic link is missing.
A person with Tourette's has about a 50% chance of passing the gene(s) to one
of his or her children, but Tourette's is a condition of variable expression
and incomplete penetrance.Thus, not everyone who inherits the genetic vulnerability
will show symptoms; even close family members may show different severities
of symptoms, or no symptoms at all. The gene(s) may express as Tourette's, as
a milder tic disorder (transient or chronic tics), or as obsessive compulsive
symptoms without tics. Only a minority of the children who inherit the gene(s)
have symptoms severe enough to require medical attention. Gender appears to
have a role in the expression of the genetic vulnerability: males are more likely
than females to express tics.
Non-genetic, environmental, infectious, or psychosocial factors while not causing Tourette's,can influence its severity.Autoimmune processes may affect tic onset and exacerbation in some cases. In 1998, a team at the National Institute of Mental Health proposed a hypothesis that both obsessive-compulsive disorder (OCD) and tic disorders may arise in a subset of children as a result of a poststreptococcal autoimmune process.] Children who meet five diagnostic criteria are classified, according to the hypothesis, as having Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS).This contentious hypothesis is the focus of clinical and laboratory research, but remains unproven.
The
exact mechanism affecting the inherited vulnerability to Tourette's has not
been established, and the precise etiology is unknown. Tics are believed to
result from dysfunction in cortical and subcortical regions, the thalamus, basal
ganglia and frontal cortex.Neuroanatomic models implicate failures in circuits
connecting the brain's cortex and subcortex,and imaging techniques implicate
the basal ganglia and frontal cortex.Some forms of OCD may be genetically linked
to Tourette's.A subset of OCD is thought to be etiologically related to Tourette's
and may be a different expression of the same factors that are important for
the expression of tics.The genetic relationship of ADHD to Tourette syndrome,
however, has not been fully established.(1)
source
: wikipedia