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Tourette Syndrome (TS) is a neurological disorder characterised by sudden rapid, involuntary movements called tics, which occur repeatedly.
TS, sometimes also known as multiple tic disorder or tic spectrum disorder, is thought to be an inherited neurological condition which affects more than 300,000 children and adults in the UK. In most instances it starts in childhood, and for about half of children with TS, the condition continues into adulthood. In most cases TS is also linked to other behaviours, most often OCD and Attention Deficit Disorder (ADD).
Symptoms can include bouts of motor and vocal tics and the focus of these tics tends to wax and wane over time. Typically tics increase as a result of stress or tension, and may decrease when relaxed or absorbed in a task. However, symptoms are an individual phenomenon, with people exhibiting many different symptoms, perhaps over the course of their lifetime. Tics are experienced as an irresistible urge (as, for example, in a sneeze) and must eventually be expressed. Many people try and suppress their tics until they can find a secluded spot in which to release them. Even then, the feeling of relief tends to be only momentary.
Two categories of tic have been identified, namely simple and complex tics. The simple type includes eye blinking, head and limb jerking, shoulder shrugging and grimacing (motor tics); plus sniffing, grunting, throat clearing and yelping (vocal tics). Complex motor tics include jumping, smelling, touching rituals, and self-injurious behaviour. Coprolalia (vocalising offensive words and phrases), Echophenomena (repeating a sound) and Echolalia (repeating a word or phrase just heard) constitute complex vocal tics.
Contrary to popular belief, often portrayed by the media, 90% of people with TS do not swear uncontrollably.
The range of tics, or tic-like symptoms that characterise TS, is very broad and they can exist in different combinations. For a diagnosis of TS to be made, the onset of symptoms must be before the age of 18 years.
There are a number of additional behaviours thought to be associated with TS, although they are not necessary in order for a diagnosis to be established. Specifically, they include Obsessive Compulsive Disorder (OCD) and Attention Deficit Hyperactivity Disorder (ADHD). In addition, some studies suggest a link between TS and Learning Disabilities (eg reading and writing difficulties, perceptual problems), difficulties with Impulse Control (eg socially inappropriate acts) and Sleep Disorders (eg frequent awakenings or walking/talking in one’s sleep). However, the evidence supporting such a link is not conclusive at this stage.
In terms of cause, genetic studies show that TS is inherited as a gene or genes, there being a 50% risk of the gene being transmitted with each separate pregnancy.
Gender also influences the expression of the gene, with the incidence of TS being at least 3 to 4 times higher in males than in females. The gene defect is believed to cause an abnormal metabolism of neurotransmitters within the nervous system and as yet there is no known cure for the disorder, only symptomatic relief.
However not everyone with TS experiences symptoms severe enough to require medical attention and most people with tic disorders tend to improve in adulthood.
Tourette Syndrome and OCD
The clustering of OCD and TS within families suggests a common inherited factor, with TS often being complicated by co-morbid OCD. The estimated incidence of this ranges from 35% to 50%. The incidence of TS in OCD is lower (5% to 7%), although tics are reported in 20% to 30% of individuals with OCD. A distinction can be made between tic-related and non-tic-related OCD.
The most striking similarity between TS and OCD is that both are characterised by apparently senseless repetitive behaviours. Motor tics in TS are often described as ‘irresistible’, as although they can be delayed, they must ultimately be performed. Once the tic has been performed, until it feels ‘just right’, a sense of relief is then experienced. This type of phenomenon also occurs with obsessions and compulsions.
OCD with co-morbid tics appears to respond differently to treatment compared with non-tic-related OCD. In addition to anti-obsessional drugs (eg SSRIs such as Fluvoxamine and Paroxetine), individuals with TS seem to respond better to a combination of SSRI and neuroleptic treatment (eg Sulpiride and Pimozide), although there have been no good trials undertaken in this area at all.
Current theory suggests that immunological alterations may have occurred in individuals with OCD, either through haemolytic streptococcal or viral infections during childhood. An antigen has been shown to be stable in different populations over time, and is present in individuals with childhood OCD, Tourettes Syndrome, chronic tic disorder and autism. It is possible that the antigen could be linked to the motor component of the various disorders. However, much further research is required in this area, and it is probable that there aremultiple factors that have the ability to trigger OCD symptoms according to individual vulnerability, with genetically-based theory and exposure to infection being two of the likely contributors.