How is tourettes caused?

Answer 1

Genetic factors are believed to play a major role in the development of TS. Several chromosomal regions have been identified as possible locations of genes that confer susceptibility to TS. Some family studies have indicated that TS is inherited in an autosomal dominant manner. In an autosomal dominant condition, an individual has a 50% chance to pass the gene to his or her children. Not everyone who inherits a TS gene will show symptoms. Approximately 70% of females and 99% of males with a TS gene will express symptoms. An individual who inherits the TS gene may develop TS, a milder tic disorder, obsessive-compulsive disorder (OCD) without any tics, or no signs of TS. The gender of a person influences the expression (the disease symptoms and severity) of the TS gene; males are more likely to have TS or tics and females are more likely to have OCD. Approximately one in ten children who inherit the TS gene from a parent will show symptoms that are severe enough to warrant medical treatment.

Non-genetic factors are also believed to contribute to the development of TS. In about 10-15% of cases, TS is not genetic. Certain stressful processes during gestation (pregnancy) or at the time of birth may increase the chance for a person to develop TS. For example, it is known that when both twins have TS, the twin who weighed less at birth tends to have more severe tics. Other non-genetic factors that may predispose a person to TS include: severe psychological trauma, recurrent daily stresses, extreme emotional excitement, PANDAS (pediatric autoimmune neuropsychiatric disorder with streptococcal infection), drug abuse, and certain co-existing medical or psychiatric conditions. In PANDAS, children experience an abrupt onset of TS symptoms and/or obsessive-compulsive symptoms following a strep throat infection.

It is thought that TS is the result of abnormal metabolism of a neurotransmitter (a chemical in the brain that carries signals from one nerve cell to another) called dopamine and possibly of other neurotransmitters including serotonin and norepinephrine. As of December 2003, the exact mechanisms by which the TS gene or genes lead to disease symptoms were unresolved. It is hoped that locating the gene or genes responsible for TS will improve understanding of how TS develops and eventually will lead to more effective treatments.

Tics seen in patients with TS can range in intensity, frequency, duration, type and complexity. Although there is wide range of severity observed in TS, the majority of cases are mild. A minority of patients has symptoms that are severe enough to interfere with daily functioning. In the most severe cases, patients experience numerous debilitating tics during all waking hours. Tics usually occur in "bouts" with many tics over a short interval of time. Many patients experience waxing and waning (fluctuations in severity) of their tics over the course of weeks or months. Tics can be made worse by stress or fatigue and tend to improve when the individual is absorbed in an activity or task that requires concentration. Although the tics associated with TS are involuntary (not deliberate), people with TS can sometimes control their tics for a period of time ranging from minutes to hours. However the tic must eventually be expressed and will come out. Coprolalia, a sensationalized type of tic in which people make obscene or socially inappropriate comments, is present in less than 15% of TS patients.

Tics are classified as either simple or complex. Simple tics are sudden, repetitive movements that involve a limited number of muscle groups. Simple motor tics are fast and without purpose. They can cause both emotional and physical pain (such as head jerking or jaw snapping). Simple vocal tics are meaningless sounds or noises. Complex tics are coordinated patterns of stepwise movements that involve multiple muscle groups. Complex motor tics appear slower and more deliberate than simple motor tics. Complex vocal tics involve meaningful words, phrases or sentences. Tourettes can be caused by breast feeding from mothers with Mercury tooth fillings. Use of forceps to remove the infant from the vagina during childbirth and the like.

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