TTAG Global Research Committee commenting on the article:
Müller-Vahl KR et al: Functional Tic-Like Behaviors: A Common Comorbidity in Patients with Tourette Syndrome.
Functional symptoms are physical symptoms without an obvious physical cause. Historically, they are usually seen as somatic manifestations of psychological distress. Importantly, these symptoms are produced in a completely unconscious way and should not be confused with malingering. In neurology, frequent functional symptoms are tremor, seizures and limb weakness. Before the COVID-19 pandemic, functional tics were considered a rarity in neurological clinics. Since 2020 however, probably fueled by anxiety and social media consumption, rates of functional tics have significantly increased across the globe. Also, since they do not not correspond, strictly speaking, to tics, they have been renamed functional tic-like behaviours (FTLB).
In contrast to typical neurodevelopmental tics, FTLB tend to develop later (during adolescence or early adulthood), usually in an abrupt and explosive fashion. Also, they tend to be more complex from the outset and often include coprophenomena (obscene words and gestures) and self-injurious behaviors.
Despite these differences, making a clear distinction between neurodevelopmental and FTLB is not always easy or straightforward. Also, we know from other functional neurological disorders that functional symptoms often develop on top of a preexisting neurological condition, exacerbating it but not creating it from scratch. In other words, somatic and functional symptoms can co-exist and co-occur in the same person, thus blurring the diagnostic categories.
According to the fascinating paper by Müller-Vahl and colleagues, tics are no exception to what we witness with tremor or seizures. In a a cohort of +1000 people with TS, they identified 71 individuals who has both neurodevelopmental tics and FTLB. The latter tended to appear on average 15 years after the onset of primary tics. Also, (i) they tended to be female, (ii) have more coprophenomena‐like symptoms, (iii) have atypical influential factor, (iv) have atypical descriptions of premonitory sensations, (v) have higher rates of co-existing obsessive‐compulsive disorder and (vi) have higher rates of self‐injurious behaviours. Importantly, the presence of FTLB should not trigger a therapeutic escalation, since they are often considered to reflect resistance to treatment, and can even be considered an indication for deep brain stimulation.
In conclusion, you can have both neurodevelopmental tics and FTLB ! However, the latter tend to appear much later, tend to seem more severe and resist to the usual treatment for tics. Therefore, instead of pushing drug doses or even considering neurosurgery, these patients likely require psychotherapy centered on anxiety and precipitating factors. Also, these symptoms can completely remit, which is a positive message that needs to be conveyed to patients and families.
Müller-Vahl KR, Pisarenko A, Fremer C, Haas M, Jakubovski E, Szejko N. Functional Tic-Like Behaviors: A Common Comorbidity in Patients with Tourette Syndrome. Mov Disord Clin Pract. 2024 Mar;11(3):227-237.