What is Tourette's Syndrome? Tourette's Syndrome, sometimes referred to as Gilles de la Tourette's Syndrome, is a developmental neurological disorder that lies at the severe end of a spectrum of tic disorders, and is characterised by the presence of multiple motor tics and one or more vocal tics. Such tics can occur many times during a single day, and are present on most days, or, intermittently over a period of longer than a year.Tourette's Syndrome is named after the French neurologist, Georges Gilles de la Tourette who in 1884, whilst working as an intern at the famous Salpetriere Hospital in France, reported nine patients who presented with compulsive tics. Gilles de la Tourette referred to this disorder as “les maladies des tics”, which means “the illness of tics”. Amongst this group of patients was a young noble woman, the Marquise de Dampierre, who achieved notoriety for the blasphemous nature of her vocal tics which persisted until her death at the age of 80 years. Several historic figures are thought to have suffered with Tourette's Syndrome including Samuel (Dr) Johnson and Mozart.What are tics? Tics are unwanted, highly stereotyped and repetitive behaviours which occur in short sudden bouts. They include a wide range of movements from simple motor and vocal movements — common tics include eye blinking, head jerking, grunting and throat clearing — to coordinated sequences of movements, such as hand gestures, bending or complete utterances. Tics vary in the degree of muscle force involved. Some tics are less forceful than comparable voluntary movements, while others are more forceful and exaggerated. Tics are exacerbated by stress and fatigue and reduced during times of concentration. Some tics are preceded by premonitory sensations or urges that are temporarily relieved by the expression of the tic.What is the natural history of Tourette's Syndrome? Tourette's syndrome follows a common developmental course. It typically appears between the ages of five and seven years of age, with tic severity peaking around the age of 12–13 years, before abating in most individuals by early adulthood. Adults with Tourette's Syndrome are atypical and include more severe cases who do not respond to treatment.Tics fluctuate in type, complexity and severity. A specific tic may be present for several months, decrease in frequency, before suddenly disappearing completely. Tics can be suggestible; talking about an old tic may be sufficient to reinitiate it in. A small minority of patients have socially inappropriate tics, for example they utter obscene words (coprolalia) or make obscene gestures (copropraxia).Can tics be controlled voluntarily? Many Tourette's Syndrome patients can inhibit or delay the onset of their tics, particularly when they feel embarrassed by their occurrence, as when at school or work. Some individuals report they can suppress their tics for several hours; others say that their tics can only be inhibited for a few seconds or minutes. Suppressing tics invariably feels uncomfortable and frequently results in an increase in the number and severity of tics when released from active suppression. Furthermore, suppressing tics is a tiring activity and while engaging in this activity the individual can appear distracted.What is the incidence of Tourette's Syndrome? The incidence of Tourette's Syndrome in the population depends on the criteria used. Transient tics, lasting less than a month, are quite common in children, affecting around 2–4%. Estimates of Tourette's Syndrome vary between 0.5–1%, with higher prevalence rates observed in more recent studies. Tourette's Syndrome is between four and five times more common in boys than girls. Patients with Tourette's Syndrome commonly have an additional developmental condition, most often Obsessive Compulsive Disorder (40–60%) or Attention Deficit/Hyperactivity Disorder (40–90%). These disorders are associated with deficits in inhibitory control. Other co-morbid conditions include mood and anger control difficulties. Long-term outcomes are most positive for those without associated Attention Deficit/Hyperactivity Disorder. Co-morbid conditions may require pharmacological treatment. Tourette's Syndrome, without any associated co-morbid conditions, may only require medication in severe cases, where social functioning is affected.Is Tourette's Syndrome inheritable? There is a strong genetic component to Tourette's Syndrome. Both tics and Obsessive Compulsive Disorder are over-represented in families with Tourette's Syndrome. Monozygotic twin studies indicate high but not complete penetration rates, with low concordance rates in dizygotic twins. Several loci are thought to be involved and non-genetic factors — occurring before birth, perinatally or during childhood — are also thought to influence the expression of the disorder. Recently, a sequence variant on chromosome 13 was found to be associated with Tourette's Syndrome in a single child. The gene involved, SLITRK1, has been implicated in dendrite growth and the regulation of neural development. However, only a small percentage of individuals with Tourette's Syndrome are thought to have this gene mutation.What causes Tourette's Syndrome? The neural basis of Tourette's Syndrome is currently unclear, but there is convincing evidence for abnormal functioning of the basal ganglia. Basal ganglia dysfunction is also implicated in Obsessive Compulsive Disorder and Attention Deficit/Hyperactivity Disorder, though there may be differences in the circuits involved in each disorder. The basal ganglia comprise various brain nuclei, including the caudate and putamen (striatum), subthalamic nucleus, globus pallidus and substantia nigra, which connect to the cortex via five parallel circuits. They project to the thalamus and brainstem. Imaging studies have shown a number of basal ganglia structures are reduced in size in Tourette's Syndrome, though there are differences between adults and children. The most consistent reported reduction, in adults and children, is in the size of the caudate. Reduced caudate size in childhood is predictive of tic severity.In neurologically healthy individuals, the basal ganglia is involved in the regulation of motor and cognitive responses, including the selection and maintenance of behaviourally appropriate responses and the suppression of inappropriate responses. Thus the function of the basal ganglia corresponds to the key features of Tourette's Syndrome. The basal ganglia is also involved in habit learning, which is disrupted in Tourette's Syndrome. Differences are also found in cortical structures (dorsolateral prefrontal cortex, orbitofrontal, supplementary motor area and sensorimotor cortex).What causes tics? It has been suggested that tics result from reduced striatal inhibition. Clusters of striatal neurons may be activated inappropriately, resulting in inhibition of Globus pallidus pars internal or Substantia nigra pars reticula neurons, the disinhibition of excitatory neurons in the thalamus leading to hyper-excitation of cortical motor regions and an increase in unwanted movements. In support of this hypothesis, post-mortem studies have shown reduced striatal interneurons in Tourette's Syndrome. Dopamine transmission is also abnormal, with dopamine antagonists and receptor blockers successfully reducing tics.Why do tics typically remit in adulthood? It has recently been suggested that Tourette's Syndrome may be caused by a delay in the timing or extent of basal ganglia development. During childhood the density of nigrostriatal pathways decreases, while neocortical dopaminergic pathways increase in non-human primates until adolescence. Frontal plasticity may also compensate for a deficit in basal ganglia functioning. There is evidence to suggest that adults with Tourette's Syndrome make more extensive use of frontal and frontal-medial circuits to inhibit voluntary motor responses, compared with unaffected individuals. These same networks are used during tic suppression.Chronic use of these networks for tic suppression may result in a generalised move towards increased cognitive control. Indeed, recent evidence shows that children with Tourette's Syndrome but no additional neurodevelopment conditions are better than age-matched controls at tasks that require high levels of cognitive control or self-regulation, such as repeatedly switching between different motor responses.