Clinical presentation of tics and Gilles de la Tourette syndrome

Tics are the most common hyperkinetic manifestations during development. The clinical phenomenology of motor tics ranges from mild twitches affecting a single facial muscle to orchestrated contractions of different muscular districts resembling purposeful behaviors. Likewise, the repertoire of vocal tics (also called phonic tics) covers the whole spectrum between isolated grunting noises and meaningful strings of words. Simple and complex tics arguably sit on a continuum of symptom severity and respond to the same treatment interventions. The diagnosis of Gilles de la Tourette syndrome (GTS) is based on the presence of multiple motor tics plus at least one vocal tic, with onset before the age of 18 years and chronic course. It has been argued that the different tic disorders belong to a spectrum of increasing complexity, from the transient form (provisional tic disorder), through persistent motor or vocal tic disorder, to GTS. However, the clinical phenotype of GTS stands out because of the frequent association with specific behavioral problems, ranging from tic-related obsessive-compulsive disorder to other neurodevelopmental conditions. The diagnosis of tic disorders is based on clinical observation and requires expertise. The recent outbreak of functional tics, documented across several countries during the COVID-19 pandemic, introduced unprecedented challenges to the differential diagnosis of neurodevelopmental tics.