The Puzzle of Tourette's

As this last paper approached, I was having major difficulties trying to think of a topic to choose. I knew I wanted to do something with a lot of scientific evidence about it, but also something that was still a little bit of a mystery. After searching the internet, I finally came upon a subject that seemed to meet these criteria, Tourette’s syndrome. Tourette’s syndrome was first described in 1885 and since then has only increased in recognition and controversy. (1) Wikipedia defines Tourette’s as, “an inherited neurological disorder with onset in childhood, characterized by the presence of multiple physical (motor) tics and at least on vocal (phonic) tic.” (1) This definition is well and good, but what is the cause of these tics, who do they affect, and what can be done to stop them?

The first task I undertook was to find out just how common Tourette’s syndrome is. The National Institute of Health estimates that approximately 100,000 Americans have Tourette’s (4) and Lawrence Scahill of Yale Child Study Center estimates that 1 in 1000 to 1 in 100 people in the world have Tourette’s. (2) Tourette’s is such a wide-spread disease that it is slowly becoming more and more recognized. There is a Tourette Syndrome Association that was founded in 1972 and more recently Dr. Roger D. Freeman of The Neuropsychiatry Clinic at British Columbia Children’s Hospital has started a blog about Tourette’s to help educate people.

After finding out how many people this syndrome affects, I wanted to learn how who it affects and how. It has been found that Tourette’s tends to run in families and is much more common in boys than it is in girls. (2) It has actually been found that there is a ratio of 3:1 of boys with tics versus girls with tics. (3) These facts leads scientists to believe that Tourette’s a genetic, inherited disease, but the exact location of the gene(s) responsible has yet to be found. It has been postulated, however, that several regions of chromosomes are involved and that all the genes in these regions can act differently to cause different severities of Tourette’s. (2) Another reason scientists have to believe that there is a genetic component is the fact that only 11-20% of people with Tourette’s only have Tourette’s, the rest have, on average, up to two other disorders. The most common connections are with OCD and ADHD, which are hypothesized to all share brain circuits. (3)

Following this research on the genetics of Tourette’s, I proceeded to look into what are the neurological causes for Tourette’s. The main tool that has been used to see the neurological causes is brain imaging, which has led scientists to make three important conclusions which I shall discuss in a step by step manner. The first conclusion that scientists have been able to make is that people with Tourette’s syndrome have different localized brain activity than people who do not have Tourette’s.  However, these differences are also varying among people with Tourette’s. (2) This further supports the idea that Tourette’s is caused by multiple genes that all have varying affects. These genes would lead to the unique nature of Tourette’s from patient to patient but would also account for the similarities between all cases of Tourette’s.
The next conclusion that scientists have been able to make is that the basal ganglia seems to be the affected part of the brain that leads to Tourette’s. The basal ganglia are a group of connected brain structures that is below the cerebral cortex. The basal ganglia is basically a connection between what the brains “wants” to do and the muscles and nerves that can carry out these wishes. (2) In people with Tourette’s it appears that the basal ganglia lose the ability to inhibit undesired movements that the brain “thinks” of, thus creating tics. It is also thought that since the basal ganglia receives signals from every part of the cerebral cortex; the different strengths of Tourette’s and its connection to other disorders could be a direct result of the basal ganglia losing its ability to inhibit some things. (2) This fact can make it difficult to separate Tourette’s from the disorders that are connected with, for example to separate a compulsion from a tic. (3)

The final conclusion scientists have been able to make is that dopamine appears to be a contributor the malfunctioning of parts of the basal ganglia. Brain imaging has revealed that people with Tourette’s have an increased amount of dopamine-containing neurons in a specific part of the basal ganglia. Also a large majority of the medications that are currently used to control Tourette’s involve blocking dopamine receptors. (2) It is also thought among some scientists that serotonin is also involved. (4) However, there is no more specific evidence concerning these neurotransmitters and their contribution to Tourette’s. It is an area of research that scientists are looking into, because it could hold the key to curing or permanently controlling Tourette’s.

The above conclusions about Tourette’s are accepted by pretty much every scientist and academic that studies Tourette’s. However, there is one theory regarding Tourette’s that is highly controversial involving the effects of illnesses, specifically Streptococcus, on Tourette’s. There is a group of scientists, PANDAS, led by Susan Swedo, who works at the National Institute of Mental Health, who believe that strep infections can cause Tourette’s in some children. There have also been studies that have shown that the strep antibodies can damage the basal ganglia in some children. Swedo has done experiments that involve prescribing anti-biotics to children on a long term basis. (2) It seems to be working, but the interpretation of the results so far has been very subjective and is doubted by many other scientists. But the theory is still being looked into to and could provide another piece to the puzzle of Tourette’s.

Tourette’s also has a very different public and scientific appearance. While to most people Tourette’s is a disorder of uncontrollable movements, those with Tourette’s and doctors who study Tourette’s have debunked this idea. John Piacentini, a specialist, has described Tourette’s as a positive feedback loop; it is basically an urge that is expressed and then a feeling of relief follows, which encourages further actions. (2) This idea is supported by the fact that people with Tourette’s can suppress their tics for a time. This has led to treatments beyond the dopamine medications or antibiotics mentioned above. Psychotherapy, counseling, and behavior therapies are all used to try and control or at least decrease the expression of tics. It is also common to teach a person how to substitute a more acceptable tic then the one they express. (4) These techniques have also been shown to work in many cases.

When I started the research for this paper, I was expected all my answers to be answered about what causes Tourette’s. Tourette’s seems so specific, there are specific movements and vocal tics associated with it, that I didn’t think it was possible for the causes of this disease to not be concretely known. However, I know see that this belief was not true. Tourette’s is a syndrome with many facets and dimensions. It is a genetic defect, a neurological defect, a result of infectious diseases, and a syndrome caused by a positive feedback loop. None of these causes can completely explain Tourette’s, but none of them can be completely connected together either. Research is being conducted to find the exact genetic cause, the exact neurological cause, and the exact cause of infectious diseases. There are many questions that need to be answered, and I shall look forward to these answers.

Sources:
1. “Tourette syndrome.” Wikipedia. 7 May 2007. Wikimedia Foundation Inc.
      <http://en.wikipedia.org/wiki/Tourette_syndrome>
2. Olson, Steve. “Neurobiology: Making Sense of Tourette’s.” Science. September 2004.
      AAAS. <http://www.sciencemag.org/cgi/content/full/305/5689/1390>
3. Freeman, Roger D. Tourette syndrome: Minimizing Confusion. 8 March 2007.
 <http://www.tourette-confusion.blogspot.com>
4. “Tourette Syndrome: Frequently Asked Questions.” Tourette Syndrome Association,
      Inc. 2005. <http://www.tsa-usa.org/Medical/Faqs.html>