Professor Valsamma Eapen ( left ) Chair of infant , child and adolescent psychiatry , UNSW Sydney ; head of the academic unit of child psychiatry , South West Sydney Local Health District , Sydney , NSW .

Associate Professor Daryl Efron ( right ) Consultant paediatrician , Royal Children ’ s Hospital ; senior research fellow , Murdoch Children ’ s Research Institute , University of Melbourne , department of paediatrics , Parkville , Victoria .

Copyright © 2021 Australian Doctor All rights reserved . No part of this publication may be reproduced , distributed , or transmitted in any form or by any means without the prior written permission of the publisher . For permission requests , email : howtotreat @ adg . com . au .

First published online on 15 January 2021

BACKGROUND

GILLES de la Tourette syndrome ( GTS , more commonly known as ‘ Tourette syndrome ’, Tourette disorder or simply Tourette ’ s ) is a neurodevelopmental disorder characterised by the presence of multiple motor and one or more vocal tics of more than one year ’ s duration . ¹ GTS has an onset during childhood and follows a waxing and waning course , with one type of tic being replaced by another .

It was first described by Itard in 1825 , and subsequently in 1885 , French neuropsychiatrist Georges Gilles de la Tourette provided a detailed account of the clinical features . Until the 1970s , GTS was considered a rare disorder and something of a medical curiosity . As a result of recent epidemiological work , however , we now recognise tic disorders as relatively common but underrecognised in the community and a significant cause of hidden disability .

Tics are frequently not recognised as they may be masked by comorbid behaviours and other neurodevelopmental or mental health difficulties . Therefore , they may not be noted or

enquired about among the presenting

complaints . Tics can also be misconstrued as deliberate actions , especially in patients with comorbid challenging behaviours . GPs who see children and adolescents , particularly patients with behavioural and learning difficulties , will very likely have at least several cases of GTS in their case mix , but at times , the diagnosis of tics may be missed among the other comorbidities . The correct identification of a tic disorder can be extremely

helpful — not only for diagnostic formulation and management , but also for the patient and family ’ s own understanding of their experiences .

This How to Treat discusses the signs and symptoms , prevalence , pathogenesis , assessment and diagnosis , as well as management , including when to refer and prognosis .

PREVALENCE

THE prevalence of GTS is now understood to be about 1 % in school-aged children in the general population . ² GTS occurs in people of all cultures , racial groups and social classes , with some degree of uniformity of the core features but with variability in

the comorbid conditions . ² The age

at onset of symptoms ranges from 2-15 years , with a mean age of 6-7 . The severity of tics is age dependent , with peak severity between 8 and 12 . Tics improve with age ( with remission observed in 30 – 50 %). ² It is thus important to consider the age of the cohort when interpreting epidemiological findings . GTS is more common in boys than in girls , with a male-tofemale ratio of 3 – 4 to 1 . ²

AETIOLOGY AND PATHOGENESIS

DESPITE significant international research efforts , the exact aetiology and pathogenesis of GTS and the interplay between genetics , brain , mind and behaviour is not yet fully understood . However , there is converging evidence to suggest involvement of the cortico – striato – thalamo – cortical circuitry ( linking specific regions in the frontal cortex to subcortical structures , including the basal ganglia and thalamus ) that mediates the integration of movement , sensation , emotion and attention ( see figure 1 ). ³

Neurotransmitters — such as dopamine

, glutamate and GABA — are

implicated in the functioning of this circuitry . Further , the improvement in tics with advancing age is thought to be due to the compensatory responses that develop in line with maturation and the frontal cortex becoming more efficiently connected to the striatum and to the motor and sensorimotor cortices . ⁴

The familial nature of GTS was evident from the time of its original description . While twin and family

studies suggest a population-based heritability estimate of 0.77 , no single susceptibility gene of large effect has been identified so far . ² The current consensus is that the condition is polygenic , with a predominant genetic risk attributable to common risk variants distributed across the genome , which is also shared by other neuropsychiatric and neurodevelopmental disorders .

The clinical presentation is considered the result of the site and extent of neurocircuitry involvement , which in turn , is influenced by gene – environment interactions . ⁵ In this regard , several contributory factors have been proposed , including prenatal

and perinatal factors ( for example ,