TOURETTE SYNDROME

Biology 202
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TOURETTE SYNDROME

Sooyoun Yi

"When my friends and I are driving somewhere, I often find myself repeating outside words I read, out loud. The conversation sometimes goes something like this: 'Laundromat.' 'What?' 'Oh, nothing.' 'Armed robbers shot.' 'Huh?' 'I was only speaking to myself...' 'Oh.' (1)."

Tourette Syndrome (TS) is a genetic neurological disorder that is characterized by involuntary muscle movements, termed tics (3). Tics can also come in the form of vocal outbursts. The range of these symptoms is very large. Some examples are rapid and repetitious blinking of the eye, clearing of the throat, jumping, or uttering words and phrases out of context (4). It has been seen that there is an increase of tics when the individual is under emotional tension, stress, or anxiety and even seasonal changes in the weather (1).

TS was first recognized over a hundred years ago by a French neurologist, George Gilles de la Tourette, who had patients with involuntary convulsive muscular movements (1). A lot more is understood now about TS than before and people have now realized that this disorder is rooted in biology and neurology (1). It can not be said that TS is a disease because having TS does not necessarily mean that they need to seek treatment. The tics are called "symptoms" only because they are seen as abnormal in our society. But in majority of the people who have TS, the tics do not interfere with everyday proceedings of life.

The tics caused by TS are completely involuntary and are caused by a chemical imbalance in the wiring of the brain. There are specific neurotransmitters that are affected - serotonin, dopamine, and norepinephrine (4). Norepinephrine is an important neurotransmitter in the limbic system, which can either suppress or stimulate other neurons. A defect in this neurotransmitter can lead to an over-activity of dopamine in the brain that may produce totally random nerve twitches. Serotonin controls sleep and it was found that people with TS had significant sleep disturbances which suggests that TS patients had some kind of defect in serotonin. Although the cause for TS has not been firmly established, it is a neurological disorder, not a psychological one. It has to be understood that the prefrontal cortex, the limbic system, the striatum, the cerebellum, the motor and sensory cortexes, and the memory network all play a role in causing the tic in TS (4).

There are many disorders that involve the same area of the brain as well as the same neurotransmitters. TS is associated with many other neurological disorders such as obsessive compulsive disorder (OCD), attention deficit hyperactive disorder (ADHD), sleep disorders, dyslexia, and disinhibition (4). Drugs that may help to combat one disorder may have the opposite effect on tics. Stimulants like Ritalin, Cylert, and Dexedrine is used to help people with ADHD but they also increase the tics of people with TS.

Drugs that stimulate dopaminergic activity in order to correct another neurological disorder may make the symptoms worse while the suppression of dopaminergic activity decreased the tics. It seems like there is a causal relationship between dopamine levels and tics.

"The rate of dopamine turnover, and the firing rate of dopamine nerves, is much higher in the prefrontal lobes than in the caudate, putamen or limbic system. This carries with it the important implication that anything that affects the rate of dopamine synthesis is likely to have a greater impact on the function of the brain. (4)"

The main areas of the brain that are affected are the frontal lobes, the limbic system, and the striatum (4). The generation of tics can be held accountable by the nucleus accumbens and the striatum (caudate-putamen) (4). A gene mutation in the DRD2 gene causes the D2 receptors to function abnormally. The hypersensitive dopamine D2 receptors, in turn, cause the over-activity of the dopaminergic neurons in these areas of the brain (4). The DAT1 gene also has been found to contribute to the tics. A normally functioning DAT1 gene is responsible for the re-uptake system in pre-synaptic dopaminergic receptors (4). A mutation in this gene may cause the system to function improperly and therefore there is a less re-uptake of dopamine, which causes tics (4). Dopamine is not the only neurotransmitter that is responsible for tics. Fluctuating levels of other neurotransmitters may cause dopaminergic over-activity and consequently generate tics (4).

Some people with TS have said that they are conscious of the urge to tic before they actually do so. They suppress the urge to tic until they are in a setting where they can release the urge but then the tics are more severe.

"If you want to imagine what tics are like: imagine being aware of the urge to sneeze without any physical sensation in your nose preceding it. Now replace 'sneezing' with any other sudden act you can think of. Or imagine the urge to close your eyes because a fly is flying straight towards them, but without there actually being any fly. Now imagine that as you resist the urge to close your eyes the 'imaginary' fly is frozen in front of your eyeballs, forever nerve-wrackingly homing in on them until you eventually have to close your eyes or jerk away your face. (1)"

The tics can be thought of as just habits rather than random nerve twitches because the tics are both unconsciously suppressible. If a person with TS finds oneself in a public situation, he may suppress the tic until he is alone which leads to a stronger outburst when the tics are finally expressed (1).

There is no cure for TS but there are drugs that can decrease the inconvenient symptoms. Since TS is considered a neurological disorder, anti-psychotic medications can be taken to suppress or stimulate certain neurotransmitters. The most widely used drug is the haloperidol (Haldol) which counteract dopamine over-activity. There has been a marked decrease of tics among people who take Haldol or other drugs to relieve the symptoms like, clonidine (Catapres), pimozide (Orap), fluphenazine (Prolixin, Permitil), and clonazepam (Klonopin) (2).

There are people who do seek psychotherapy to reduce stress - to help relax. Psychotherapy, though, can not cure TS since it is a neurological disorder that is caused by many different neuro-chemical imbalances. TS is a neurochemical problem that needs a neurochemical solution (2). Psychotherapy may help to deal with random public outbursts but the neurochemical dysfunction must be brought to a "norm" before psychotherapy can be effective (2).

The tic that the general public is most familiar with is coprolalia, swearing. Coprolalia, though, occurs in only about 8% of people with TS (1). Coprolalia is a very interesting case in that swearing is determined culturally and not biologically (1). How can a biological disorder cause someone to specifically shout out obscenities? Some explanations say that the brain associates certain words with specific emotions and this can cause someone with TS to randomly shout out profanities. Even if behavior can be associated with simply just action potentials, it seems understandable that people with TS may shout out random words but it seems unusual that overactive or under-active neurotransmitters can cause a person to shout out only curse words.

Much more is known about TS than 100 years ago when George Gilles de la Tourette discovered it but there is still much more grounds to cover. The only way to diagnose TS is by observing the symptoms. Blood tests and neurological tests have not lead to conclusive diagnosis of TS. Using coprolalia as a starting point, maybe it needs to be questioned whether or not TS is actually a neurological disorder rather than a psychological one. As with any good science, research about the TS has answered many questions but have left many more questions to be answered.

WWW Sources

1) The Facts About Tourette Syndrome , Provides explanations and questions about TS

2) Internet Mental Health , Medical viewpoint about TS - in depth explanation of medications

3) Tourette Syndrome Association, Inc. , Good starting point for research about TS

4) The Tourette Syndrome Phenomenon , Wealth of info about TS from a person who has it

5) Yahoo! Health , Shortened encyclopedia definition of TS