Case scenario

Eight-year-old Tom was referred by his general practitioner (GP) asking whether his movements and behaviour were tics. His parents reported noticing intermittent facial grimacing movements and grunting for the last six months. They report that it happens both at home and in school and was worse a few weeks back when they had consulted the GP. The GP advised that the episodes should be ignored, and since then they have been less frequent.

What are tics?

Tics are sudden recurrent individually recognisable vocalisations, intermittent movements or movement fragments that are almost always briefly suppressible and are usually associated with awareness of an urge to perform the movement.1 Suppression of a tic usually leads to growing discomfort, which is alleviated by performing the tic. Characteristic features of tics are predictability of movement, predictability of onset and triggered by suggestion, sensory cues, stress, excitement or demonstration.1 ,2 Tourette syndrome (TS) is in the spectrum of tic disorders but needs to fulfil certain diagnostic criteria (see below).

Types of tics

Tics can be classified by description (table 1) and by pathophysiology (box 1). Pathologic tics can be further classified into primary sporadic, primary inherited and secondary.

Diagnostic criteria and spectrum of tic disorders including TS

Tic disorders can be diagnosed using the Diagnostic and Statistical Manual of Mental Disorders V (DSM-V)4 or the International Classification of Disease (ICD)-105 criteria and be classified as:

• provisional tic disorder (DSM-V) or transient tic disorder (ICD-10)—tics that occur on most days with a duration of 4 weeks to a year, not due to TS;

• chronic/persistent motor or vocal tic disorder—tics that occur on most days for longer than a year, not due to TS;

• TS—two or more motor tics and at least one vocal tic occurring for at least a year.

All the above must start before 18 years of age and not be due to physical conditions or medication side effect. There should not be a tic-free period of >3 months in a year.

Prevalence and natural history

Tics are present in up to 5% of the population, with a lifetime prevalence of ≥20% among boys.6 The prevalence of TS is 7.7 per 1000 children (95% CI 3.9 to 1.51).7 Motor tics usually begin between the ages of 3 and 8, and phonic/vocal tics usually follow the onset of motor tics after several years.8 Uncomplicated tics peak in the early second decade with a marked reduction in tic severity by the age of 19 or 20 years (figure 1).9

• Download figure
• Open in new tab
• Download powerpoint

Figure 1

Relationship between age and severity of tics and coexisting disorders.

The onset of TS is typically between 2 and 15 years, average of 6.4 years, and is manifested in 96% of patients by 11 years of age.10 The disorder is usually diagnosed 2–3 years after onset of tics. Peak severity of tics are usually at 9–11 years of age. Five to ten per cent of patients have an intensifying course without improvement. In about 85% of patients, however, symptoms diminish during or after adolescence11 (figure 2).

• Download figure
• Open in new tab
• Download powerpoint

Figure 2

The clinical course of Tourette syndrome.

Tics in TS affects more males than females (4.3:1).12 They are characteristically waxing and waning.2 Frequency and severity of tics in childhood is hardly predictive of tic severity in adulthood. Tics and TS are associated with other neurobehavioural conditions, particularly attention-deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) (figure 1).

Pathophysiology

The disorder likely results from a disturbance in the striatal–thalamic–cortical (mesolimbic) spinal system, in which dopamine plays an important role, which leads to disinhibition of the motor and limbic system.13 Alterations in the cortico–striato–thalamo–cortical circuits in patients with TS have been found on MRI and electrophysiological studies.14 Family studies strongly indicate a genetic component in TS, with shared genetic influences between tics and OCD. The link to ADHD, however, is unclear.14 Several loci have been identified as candidate susceptibility regions, and mutations in SLITRK1 gene15 and HDC gene16 appear to be a rare cause of TS.

Differential diagnoses

Comorbidities

TS is commonly associated with comorbidities (table 5).12 Motor and vocal manifestations are more frequent in boys, whereas girls are more likely to have behavioural problems such as OCD.

ADHD symptoms in TS occur in the majority of cases before tic onset (figure 1). In our personal experience, we found that comorbid ADHD, when present, occurred in nearly 70% of affected children before the onset of TS. ADHD symptoms tend to decrease in 20% of children during adolescence, usually following a decrease in tics. ADHD in patients with TS are associated with increased irritability and rage attacks, increased vulnerability for drug abuse, depression and antisocial behaviour. TS plus ADHD appears to be a more severe condition than ADHD alone.17

Comorbidity of TS with OCD can make distinction between complex motor tics and compulsions difficult.1 Comorbid obsessive-compulsive symptoms start at a later age (around 10 years) than tics (figure 1). Normal obsessive-compulsive-like symptoms are present in many young children, peaking at 2.5 years of age. This disorder, when associated with tics, generally has a pre-pubertal age of onset. OCD can lead to periods of depression. In our personal experience, we found OCD occurred in 50% of children with TS. Comorbid OCD and ADHD are associated with poorer psychosocial functioning.14

Assessment

Salient features of clinical assessment and investigations are outlined in table 6. Obtaining a video recording of the episode on a camera or a mobile phone is most useful in making the correct diagnosis.

Management (see algorithm) (figure 3)

Most children with simple motor tics do not require treatment. Knowledge of the temporal patterning of tics is fundamental for clinicians as it informs decisions about when to initiate or change management and when to ‘watch and wait’ after psycho-education and reassurance.2

Non-pharmacological and/or pharmacological interventions should be considered in addition to psycho-education for children with clear impairment associated with the tics19 (box 2).

In the presence of comorbid conditions (ADHD, OCD, depression), it is better to treat the comorbidities first, as successful treatment of them will often diminish tic severity.9

Non-pharmacological

Pharmacotherapy

Pharmacotherapy should only be instituted by clinicians or units who have experience of managing tic disorders and of using the medication itself. These medications are not commonly used by most paediatricians and caution needs to be exercised as their use can be associated with significant side effects. In most instances where medication is being considered, it is preferable to refer the child to a specialist unit and an experienced clinician.

There is a paucity of studies directly comparing efficacy and safety of pharmacological agents, hence no firm recommendations can be made. Pharmacotherapy probably has the fastest onset of response compared with behavioural treatments, but this experience has never been tested in a clinical trial. In our personal practice, indications for pharmacological treatment are subjective discomfort, social isolation with bullying and harassment, reactive depressive symptoms and impairment of school performance. We use non-neuroleptics like clonidine as a first-line medication. We use neuroleptics as second line when non-pharmacological treatment and first-line treatment have been unsuccessful. As tics are thought to involve the dopaminergic pathway, modulating this, particularly by blocking the post-synaptic D2-receptors, is the main action of pharmacotherapy in tics.19 Medication choice, doses and level of evidence of effectiveness are provided in table 7.

• Download figure
• Open in new tab
• Download powerpoint

Figure 3

Suggested management algorithm for children with tic disorders. CBT, cognitive-behaviour therapy; DBS, deep brain stimulation; ERP, exposure with response prevention; HRT, habit reversal training; THC, tetrahydrocannabinol.

Alternative and emerging therapies

It is recommended that in severe cases of TS not responding to conventional therapies other agents could be tried in specialised centres19 (see algorithm). This includes the use of tetrahydrocannabinol, botulinum toxin injection, deep brain stimulation and transcranial magnetic stimulation.

Schools and tics

Providing educators with general information relating to the aetiology, presentation and course of TS will help them to implement effective individualised strategies to manage classroom behaviour, thus maximising child’s learning potential.20 There is good resource on Tourette Action UK website for educators (http://www.tourettes-action.org.uk/?&filter=teachers).