9 Child and adolescent psychiatry9.7 Disorders in childhood and adolescence
9.7.2 Tic disorders
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Written by Resident Doctor Committee · Published
What a tic is
A tic is a sudden, brief, repeated, non-rhythmic and purposeless movement or vocalisation. Tics are classed on two axes: motor against vocal (phonic), and simple against complex.
Type | Simple | Complex |
|---|---|---|
Motor | Blinking, grimacing, head jerks, shoulder shrugs | Touching, jumping, echopraxia, copropraxia |
Vocal | Sniffing, throat clearing, squeaks | Words, echolalia, palilalia, coprolalia |
A simple motor tic is a brief, meaningless movement of one functionally related muscle group.
Coprolalia occurs in only about 10 to 30% of clinic samples and is not needed for Tourette syndrome.
Older children often describe a premonitory urge, such as rising neck tension, which the tic briefly relieves.
Tics can be suppressed for a limited time, usually at the price of rising tension and a later rebound.
Classification
Presentation | ICD-11 | Duration |
|---|---|---|
Multiple motor tics and at least one vocal tic | Tourette syndrome | At least a year |
Motor tics only, never vocal | Chronic motor tic disorder | A year or more |
Vocal tics only, never multiple motor tics | Chronic phonic tic disorder | A year or more |
Tics of any type or number | Transient tic disorder | Begin and resolve within 12 months |
Tourette syndrome needs onset in childhood or adolescence, and the motor and vocal tics need not occur at the same time.
ICD-11 needs tics to persist for at least a year before it allows a chronic tic disorder, and this line separates the chronic tic disorders from transient tics.
Epidemiology and course
Transient tics affect roughly 5 to 20% of children, whereas Tourette syndrome affects about 1 in 100.
Tourette syndrome is more common in males, at about 3 to 4 to 1.
Tics begin at 4 to 6 years, often in the face, and motor tics usually come before vocal tics.
Tics are usually worst at 10 to 12 years and then lessen through adolescence in most young people; about two-thirds of adults have absent or mild tics.
Severity fluctuates over weeks or months and rises with stress, fatigue, excitement and illness.
Comorbidity
Attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) are the commonest co-occurring conditions, each present in roughly half of clinical cases.
ADHD is the single most frequent in children; OCD is nearly as common overall and becomes relatively more prominent in adult life.
Comorbid ADHD, OCD or anxiety may disable a child more than the tics do.
Aetiology
Tics are highly heritable and usually polygenic, and relatives have more tics and obsessive-compulsive symptoms.
Research implicates cortico-striato-thalamo-cortical circuits, which select and inhibit movement.
Disturbed dopamine signalling in the striatum is the most widely proposed neurotransmitter abnormality, within an otherwise multifactorial aetiology.
Antipsychotics suppress tics by blocking striatal dopamine D2 receptors, in keeping with the dopamine hypersensitivity model of tics.
Telling tics from other movements
Movement | Form | Suppressible | Preceding sensation | Context |
|---|---|---|---|---|
Tic | Abrupt, non-rhythmic, recurring repertoire | Briefly | Urge, relieved by the tic | Childhood onset, fluctuating course |
Stereotypy | Rhythmic, prolonged, fixed pattern | Interrupted by distraction | Usually none | Early childhood, autism, intellectual disability |
Compulsion | Repeated to prevent harm or feel complete | Resisting raises distress | Obsession or incompleteness | OCD |
Chorea | Flowing, irregular, migrating | Usually not | None | Sydenham chorea, Huntington disease, lupus |
A regular, patterned rhythm separates a stereotypy from a tic; stress, fatigue and purposelessness occur in both.
Management
First steps
For uncomplicated tics with no impairment or comorbidity, the first step is psychoeducation, not medication: stress and tiredness make tics worse, and most tics improve.
Habit reversal training teaches awareness of the urge and a safe competing response incompatible with the tic, held for about a minute or until the urge settles.
Comprehensive Behavioural Intervention for Tics (CBIT) adds to habit reversal the changing of situations that make tics worse.
Medication
When tics still cause distress or impairment after psychoeducation and CBIT, an alpha-2 adrenergic agonist (clonidine or guanfacine) is the first drug: its effect on tics is smaller than an antipsychotic's, but its adverse effects are lighter.
Alpha-2 agonists need monitoring of sedation, blood pressure and pulse, and are tapered to avoid rebound hypertension.
Antipsychotics suppress tics more strongly; aripiprazole is commonly used, but only haloperidol holds a UK licence for tics.
Antipsychotics need metabolic and movement-disorder monitoring, and haloperidol and pimozide carry cardiac risks.
PANDAS and Sydenham chorea
PANDAS is a proposed post-streptococcal autoimmune syndrome of prepubertal children.
It is defined by abrupt-onset tics, obsessive-compulsive symptoms or both, with a relapsing, sawtooth course.
The proposed mechanism is molecular mimicry: antistreptococcal antibodies cross-react with neurons of the basal ganglia (striatum).
PANDAS and PANS bring anxiety, mood lability, sensorimotor and somatic features, but psychotic symptoms lie outside the recognised cluster.
Clinicians look for a raised streptococcal antibody titre (antistreptolysin O, anti-DNase B), yet the diagnosis remains clinical.
Sydenham chorea is the post-streptococcal neurological manifestation of rheumatic fever, appearing weeks to months after group A streptococcal infection.
Its movements are random, flowing and non-suppressible, with hypotonia and emotional and obsessive-compulsive change.
Sydenham chorea is told from PANDAS by its movements: chorea flows and cannot be held back, whereas tics are abrupt and can be suppressed briefly.