Author: Will Bowman
Tourette’s Syndrome is a neurobiological disorder that affects nearly 1 out of 160 children from 5-17 in the US alone. Neurobiological disorders are illnesses of the nervous system that can be caused by a myriad of factors, including genetic, molecular, or other biological factors. Tourette’s Syndrome (TS) is characterized by motor or vocal tics, which are involuntary, and manifest in a variety of ways depending on the person. It is common for those with TS to also have another simultaneous condition, such as Obsessive Compulsive Disorder (OCD) or Attention Deficit Hyperactivity Disorder (ADHD). Current research has not found a cure for TS, however more and more information is being revealed about how it operates, possible causes, and treatment options.
The tics associated with TS are characterized as sudden, involuntary movements or vocalizations that are rapid, recurrent, and nonrhythmic. Research has provided a neurobiological mechanism for the generations of tics, and thereby helped understand them. Within the brain, there are many different circuits and systems of neurons that fire in particular patterns. We understand that many of these circuits can have a specific role and therefore are useful in studying particular behaviors, such as a TS tic. Most of these structures are highly regulated and controlled, but when they are not we can observe and study abnormal manifestations. We understand that the primary motor cortex, a structure found to coordinate movement, can be triggered to spontaneously send out a signal due to such a dysregulated cortical circuit in the brain. It is from this circuit’s activity that researchers have traced the regulation of the pathway to dopamine and glutamine concentrations, both molecules normally found within the brain. Comparisons between normal and TS brains do reveal some differences in metabolites and protein concentrations. These differences are currently described from a genetic model. Further research has also linked immune system cells and other motor circuits to TS symptoms, which can be read about here.
The genetic cause for TS is currently being explored through large scale population studies. These studies examine the entire genome, all of the DNA, from several hundred people of European and Asian descent. These studies work by comparing the genomes of many people, and forming a statistical relationship between certain regions and having TS. Every person should normally have some different versions of genes, regions of DNA with a known function, and that difference is usually greater when two people are not closely related. The study find versions of genes that are unique or more likely to found in a person with TS. This builds a relationship between certain genes and the disorder itself. From there, researchers can narrow down which identified genes are actually relevant, and determine their function and role in TS. For example, recently a gene was located that reduced the ability of the body to make histamine, a molecule normally associated with immune responses and neuron signalling in the brain. This gene was found to be highly correlated to TS in several families, and therefore was studied. Further research on histamine has revealed that it is involved in neuron signalling and dopamine in the brain, linking it to the biological cause of TS. Of course, not all TS cases have this mutation, and other genes have also been found to correlate to TS. For more information on the role of genetics to TS, please follow this link.
Because TS can impact a person’s day to day life, and is often expressed with other disorders as well, treatment options are varied. Drug options for treatment are available, as well as therapies. Habit reversal therapy (HRT) and comprehensive behavioral intervention for tics (CBIT) have been shown to be effective, but are often paired with a drug treatment as well. The most common drug for TS treatment is currently tetrabenazine. This has been shown to affect the dopamine levels in the brain and help manage and reduce tics, however there are other options as well as this may not be for everyone. Clonidine, guanfacine, and others are also available. It should be mentioned that some of these drugs are classified as antipsychotics, which has no bearing on their effectiveness but can deter people simply because they can be used to treat other disorders. It is important to remember that every medical tool is multifunctional, certain drugs are capable of treating different disorders, and that you should not avoid treatment simply because of that fact. More information on the ways these and other drugs are used for treatment of TS can be found here.
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