Tourette Syndrome: Symptoms, Causes, and Genetics

Usually, the first symptoms of Tourette Syndrome are facial tics, commonly eye blinking. Other facial tics include nose twitching and grimaces. The next tic to appear will usually be some other minor motor tic such as foot stomping, head jerking, neck stretching, or body twisting and bending.

Affected individuals may also have a vocal tic such as clearing their throat, coughing, grunting, sniffing, yelping, barking, or shouting. Few Tourette Syndrome patients also experience coperlalia-the uttering of inappropriate or obscene words or phrases. They also may repeat words they hear others saying (echolalia).

Some individuals touch people or repeat actions in an obsessive manner. Very rarely, patients demonstrate self-harming behavior such as head banging, and lip or cheek biting; only patients with severe TS exhibit such behaviors.

Tics are random, changing in severity, number, frequency, type, and location. Oftentimes, symptoms will subside for weeks or even months at a time and later reappear.

Tourette syndrome is a neurological disorder in which too much or too little dopamine is produced in the brain. Too much dopamine causes hyperactivity. Dopamine is a neurotransmitter used in the substantia nigra and striatum which are important for movement. Other systems which can be effected by dopamine send axons from the midbrain to the forebrain, including the cerebral cortex. Recent research has shown that TS may also be an abnormality in the genes affecting the brain's metabolism of neurotransmitters in general.

Tourette Syndrome is a highly penetrant, sex influenced autosomal dominant trait that can cause different symptoms in different family members. If the offspring that carries the TS gene is male, his risk of developing symptoms is three to four times higher. In few cases, TS is sporadic and the cause is unknown. The exact chromosome or gene that causes TS is unknown, but we know it follows Mendelian inheritance and ratios. Through segregation analysis it has been found that TS was a "intermediate mode of inheritance;" meaning that the heterozygote's penetrance were not as severe as TS homozygotes. Finding the protein that causes TS may be one of the key ways in identifying the genome that codes for the enzyme causing TS.

Bibliography

1. http://content.nejm.org/cgi/content/abstract/315/16/993

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