Tics and stereotypies: A comparative clinical review.

Tics and stereotypies are the most common pathological repetitive complex motor behaviors occurring during the neurodevelopmental period. Although they may appear transiently during development without acquiring a pathological status, when they become chronic they may be distressing, socially impairing, or even, in the case of malignant tics, potentially physically harmful. Despite a certain similarity in their phenomenology, physicians should be able to distinguish them for their different variability over time, topographical distribution, association with sensory manifestations, and relationship with environmental triggers. The complex phenomenology of tics and stereotypies is constantly enriched by the characterization of novel variants, e.g. tics triggered by auditory stimuli in association with misophonia and stereotypies associated with intense imagery activity. Their pathophysiology remains partially elusive, but both animal model and brain imaging studies confirm the involvement of all the three major loops (sensorimotor, associative and limbic) within the cortico-basal ganglia circuitry. From a management perspective, the greatest advances witnessed in the last decade involve the diffusion of behavioral strategies (e.g. habit reversal training or response interruption and redirection), including the development of protocols for telehealth on online training in order to optimise access. In the context of severe tics, e.g. in refractory Tourette syndrome, there is increasing experience with deep brain stimulation of the intralaminar thalamic nuclei or the globus pallidus internus, although more research is needed to fine tune target choice and stimulation setting definition.