Is Tourette syndrome a rare disease?

This viewpoint article, with its interesting challenge to consider Tourette syndrome (TS) as a rare (or orphan) disease, has come during an unfortunate moment in time where we are experiencing a Covid associated pandemic of tic and tic-like-movements referrals (Heyman, Liang and Hedderly 2021). We are reflecting on these concepts whilst also sitting amongst an ever-increasing pile of new referrals for children and adolescents with a dramatic increase in tics and functional tic-like attacks, making the current prevalence rate far from ‘rare’.

The viewpoint paper opens with a title that, in itself, raises controversy. Should TS even be considered a disease at all? When engaging with some of the children and families with tics we often embrace terms such as developmental differences and neuro diversity so as to reduce the stigma sometimes associated with tics. We often encourage children to re-frame their tics and co-morbidities as diversity and difference in order to focus on some of the benefits this neurodiversity brings (for example heightened attention to detail, perfectionist traits or special abilities to switch attention)We routinely do this when the situation allows accepting, of course, for some of the ‘patients’ that more detailed therapeutic strategies are needed to enable individuals to achieve a therapeutic goal.  Should the term disease be therefore removed from the discussion?

The proposed postulate should probably remind us all of the lively (and fun) debate held at the European Society of Tourette Syndrome (ESSTS) in Copenhagen in 2018 (?) when we were all fortunate enough to meet face to face. At this meeting, we asked if ‘Syndrome’ within Tourette should be replaced with ‘spectrum’ instead, a discussion which helpfully involved those with lived experience of Tourette syndrome. To our unit’s surprise the vote was in favour of keeping the term syndrome, as we had personally changed to using the term Tic/Tourette Spectrum within our own clinical service in 2012. We published our rationale for this in a paediatric journal (Malik and Hedderly 2018) and our unit’s patient surveys revealed a preference for this term. We were pleased to see that our colleagues in Germany (Muller-Vahl 2019) support this preference. We feel this user-led preference for less pathologizing language supports not viewing Tourette syndrome as a disease. It would be interesting to hear the views of individuals with lived experience of Tourette syndrome about the palatability of the term “rare disease” to describe their symptoms.

This viewpoint paper provides an engaging discussion around how definitions of rarity of disease and orphan status vary depending on which area the reader sits in, whether in UK, USA or in the European Commission of Public Health. An informative point is raised about the lack of operational criteria for applying the term ‘debilitating’ and the removal if this criteria in DSM -V. The authors also point out helpfully that when using the term ‘wax and wane’ the clinicians should remember this does not just apply to the tic phenomenology but also to how impairing the symptoms are at any given time, although personally we recommend avoiding the use of the term handicap. This is so that we can fully respect people presenting with difficulties or with disability as individuals who can still have control over their own lives.

In this article, the term TS is highlighted to be used very much as an umbrella term including people with no presenting complaints and those who do not seek medical attention. The authors appear to advocate a re-evaluation of the term ‘impairment’ from the diagnostic criteria, whilst at the same time acknowledging that removing this term has had some positive benefits such as allowing for more cases to be included in genetic studies.

The final position is not entirely clear and we would like to propose the need to consider the views of a user group-the children, adolescents and adults experiencing tics and symptoms or signs of Tourette Spectrum conditions. We would propose again the need to identify different clusters and subgroups of ‘Tourette experiencers’ and, although tics will be at the core of each cluster, we would propose that the defining features of different groups should not involve markers of tic severity at all moving away from the importance placed on using the ‘tic count’.

The presence of the co-occuring conditions with a detailed formulation around driving forces to the tics are probably much more relevant (i.e. cluster groups). For example, in the novel currently exploding phenotype which (in our UK experience) has a higher representation of teenage girls with marked social anxiety and self-harm rates reaching 44%, we also see other groups with toe walking and autism traits and the emotionally dysregulated inattentive boys. The clinical cluster view involves making a patient-led, hierarchy of important ‘wishes’ to prioritise for potential modification.

We propose that the social and functional difficulties described following tics may be better viewed as primary drivers of tics in some families and not just sequalae, as mentioned in the viewpoint paper.  We understand that potentially histaminergic, serotoninergic, dopaminergic, glutaminergic genes and pathways are involved in the generation of tics and tic-like behaviour and in the co-occuring mental health associations. The decision about how rare or not a Tic cluster may be will probably depend on the old dilemma of ‘lumping vs splitting’. Some of the newer bioinformatic approaches of research will ultimately answer the question of which of the pathogenetic mechanisms underpinning the Tourette Spectrum are rarer that the others.

In conclusion, we would propose that Tourette syndrome should not be considered a rare disease due to the current prevalence rates, the potential impact on the user group and a need to consider the often frequent co-occurring symptoms. We prioritise an approach which includes the provision of a strength- and needs-based formulation. It is of course imperative to hold user-led consultations regarding these discussions. In the meantime, we would propose not calling TS rare or an orphan ‘disorder or disease’ and instead highlight that a major problem in the field is the ‘rarity’ of available and accessible treatments. In the UK the CAMHS services are overloaded and our movement disorder clinics have long waiting lists to even get to the point of diagnosis. Therapists trained in the management of tics or functional tic like episodes are scarce. Working together we must aim to address the orphan-ness or rarity of the resources to help provide solutions to the users with ever-increasing problems that we are all seeing in our clinics.

References:

Malik O, Hedderly T. Childhood tic disorders: diagnosis and management. Symposium: Neurology| Volume 28, Issue 10, P445-453, October 01, 2018

Müller-Vahl KR, Sambrani T, Jakubovski E. Tic disorders revisited: introduction of the term "tic spectrum disorders". Eur Child Adolesc Psychiatry. 2019 Aug;28(8):1129-1135.

Heyman I, Liang H, Hedderly T. COVID-19 related increase in childhood tics and tic-like attacks. Arch Dis Child. 2021 Mar 6:archdischild-2021-321748. doi: 10.1136/archdischild-2021-321748. Epub ahead of print. PMID: 33677431.