Neurodevelopmental versus functional tics: The state of the art

Abstract

Tic disorders of neurodevelopmental origin are the most common hyperkinetic disorder in childhood. In cases where both multiple motor tics and at least one vocal tic are present, with a chronic course, a diagnosis of Tourette syndrome can be confirmed. Functional movement disorders are a common type of functional neurological disorder, which has previously been referred to as hysteria and conversion, among other diagnostic labels. Functional tics have long been considered a rarer phenotype of functional movement disorder, compared to functional tremor or functional dystonia. However, during the COVID-19 pandemic, there have been multiple reports worldwide of an unexpected increase in the number of adolescents and young adults presenting with acute-onset functional tics. The differential diagnosis between neurodevelopmental and functional tics can be challenging, but a few demographic and clinical features have proven useful in assisting clinicians. Neurodevelopmental tics present with the gradual onset of simple motor and vocal tics in a rostrocaudal evolution, starting in early childhood, more commonly in boys. Conversely, functional tics often have an abrupt and explosive presentation of severe symptoms, with a later age of onset and a female gender predominance. Moreover, it has been reported that a proportion of patients with functional tics developed their symptoms after being exposed to social media content of influencers displaying similar manifestations. The etiology of the recent “pandemic within the pandemic” is likely to be multifactorial, with increased exposure to social media possibly playing a role alongside the psychosocial impact caused by the COVID-19 pandemic.

Keywords

• functional neurological disorder
• functional tics
• neurodevelopmental tics
• tic disorders
• tics
• tourette syndrome