Genetic Disorder Report (Tourette Syndrome) Evan Zhou Introduction Tourette syndrome (TS) is a genetic disorder that affects the human nervous system (particularly the part of the brain responsible for movement called the basal ganglia). It is an inherited disorder that has a 50% probability of passing down to the offspring. While some information is still limited, most studies done on tourette syndrome suggest that it is a dominant autosomal disorder. In 2010, the prevalence of tourette syndrome in Canada was about 1%. “122,884 Canadians participated in the 2010 and 2011 surveys, with 122 participants diagnosed with TS” (Jaeun Yang, 2016). Tourettes is also found to be 4 times more common in males than females. While tourette syndrome is not linked to a shorter life expectancy or any learning disability, the disorder causes involuntary physical movements or sounds to happen (tics). There is no cure for tourettes, however current medication for tourette syndrome can keep symptoms more controlled, thus improving the quality of life. Rise of Abnormality Tourette syndrome is a complicated disorder that affects the nervous system of a human. The exact cause for tourette syndrome is still unknown, but some studies say that it is an autosomal disorder meaning that it affects one of the 22 autosomes pairs in a human. In a small handful of cases, mutation of the SLITRK1 gene (gene used to create proteins for brain and nerve cell development) has been discovered. The causes for tourettes are unable to be pinpointed but some scientists also believe that tourettes can also result from environmental factors and not a change or mutation of a gene. Image of Labelled Human Karyotype Image of SLITRK1 gene Diagnosis Although there is no test to diagnose someone with tourettes, there is a criteria that doctors follow. To be diagnosed with tourettes, both motor tics (movements) and vocal tics (verbal) must be present, tics have to occur several times everyday, and tics are not caused by medications or other medical conditions. Usually, symptoms arise in children around ages 6-8 Graph of Other Conditions Often Linked to Tourettes with the latest being around 18. However, there are some other conditions like ADHD that can cause tics. In these cases, a doctor might recommend a blood test or an MRI to eliminate the possibility of another condition. Someone with tourettes can also be diagnosed with ADHD/ADD, behavioural problems, anxiety, depression, or learning disabilities. Although MRI’s can show the difference between someone with and someone without tourettes, No laboratory tests and brain scans have been developed to diagnose tourette syndrome. Inheritance Patterns Many studies on the inheritance of tourette syndrome have suggested that there is a probability of about 50% to pass down the gene to an offspring. Some scientists believed that tourette syndrome was caused by one gene while others believed it was a combination of multiple. While an offspring can have the gene, they may not show symptoms of tourettes. Tourette syndrome is also known to affect more boys than girls. When shown signs of tourettes, commonly asked questions from the doctor include family health history. Treatments & Medication Even after many decades of studying tourettes, there is still no treatment for it. However, there are a few medications that can reduce the intensity of tics. Medications that block or lessen dopamine can be given to patients with tourette syndrome. “Fluphenazine, haloperidol (Haldol), risperidone (Risperdal) and pimozide (Orap) can help control tics”. These medications can also lead to weight gain and involuntary repetitive movements. Tetrabenazine may also be recommended by a doctor, although it can cause severe depression. In some cases, an injection of botulinum into a muscle can be used to relieve a muscle of a motor tic. Tourettes can often be linked to depression or anxiety because of public judgements or use of medication with the side effects of depression. Psychotherapy can be offered for people in these circumstances. A newly developed therapy called deep brain stimulation (DBS) is also being developed to help with severe tics that can’t be stopped with other medication and therapy. DBS involves the implantation of a battery-operated medical device that sends stimulations to areas of the body involving movement. Sometimes, the frequency of tics can also depend on someone’s surroundings. Tics are believed to occur more frequently during stressful situations and when one is fatigued or ill. Developing Treatments To this day, tourettes is still highly researched as knowledge of the causes, inheritance patterns, and treatments are still limited. DBS (deep brain stimulation) is a new (still being developed) therapeutic method used to treat severe tics. With the research of DBS, there is also a rise in discussion about the ethical issues. DBS requires an implant of a battery device used to deliver stimulation signals to body parts of movement. Thus, discussion about the risks of implantation of a man-made device are highly considered. Another technique being developed is the medical use of marijuana. TAA (Tourettes Associations of America) is a charity funding the development of new treatments like medical marijuana. Research on use of medical marijuana is being done in order to find new medications without significant side effects. Marijuana is classified as a depressant drug because it slows down signals from the brain. Therefore, marijuana could possibly decrease the frequency of tics. While some medical marijuana is already being used for some patients in Canada, some patients reported that there was no effect at all. The use of medical marijuana is a very controversial topic. Marijuana use is illegal in many places in the world because of the high recreational use. marijuana is also a depressant drug, so there are some risks with the usage. Thus, debates about ethical issues usually happen. While tourette syndrome is a complicated disorder with little known information, progression on new medication and treatments are being developed every year. Citations Stimulating research gives new treatment hope for Tourette Syndrome. (2020, June 04). Retrieved from https://www.sciencedaily.com/releases/2020/06/200604152106.htm Risk Factors and Causes for Tourette Syndrome. (2020, May 13). Retrieved from https://www.cdc.gov/ncbddd/tourette/riskfactors.html Tourette syndrome. (n.d.). Retrieved from http://www.healthofchildren.com/T/Tourette-Syndrome.html Tourette syndrome: MedlinePlus Genetics. (2020, August 18). Retrieved from https://medlineplus.gov/genetics/condition/tourette-syndrome/#causes Yang, J., Hirsch, L., Martino, D., Jette, N., & Pringsheim, T. (2016, April 05). The Prevalence of Tourette Syndrome in Canada: A National Population-Based Study (P1.047). Retrieved from https://n.neurology.org/content/86/16_Supplement/P1.047 Mandal, D. A. (2019, February 27). Tourette Syndrome Prognosis. Retrieved from https://www.news-medical.net/health/Tourette-Syndrome-Prognosis.aspx Tourette syndrome. (2018, August 08). Retrieved from https://www.mayoclinic.org/diseases-conditions/tourette-syndrome/diagnosis-treatment/drc20350470 Tourette's Disorder: Tic Triggers. (n.d.). Retrieved from https://myhealth.alberta.ca/health/Pages/conditions.aspx?hwid=ug1096 Glickman, A., & Sisti, D. (2020, April 01). Prescribing medical cannabis: Ethical considerations for primary care providers. Retrieved from https://jme.bmj.com/content/46/4/227
