Neuromodulation for Tourette syndrome: current techniques and future perspectives

Tourette syndrome (TS) is a chronic tic disorder characterized by motor and vocal tics. Neuropsychiatric symptoms are nearly universal in TS, particularly attention deficit hyperactivity disorder and obsessive-compulsive disorder. TS can have substantial effects on quality of life, social and intellectual development, opportunities, relationships, and more. Treatment options are limited; the most common being behavioral therapy and pharmacological interventions, such as antipsychotics and anti-adrenergic agents, often yielding unsatisfactory benefits. Neuromodulation, the alteration of neural pathways and networks under external stimulation, has been established as a viable treatment strategy for specific aspects of TS. Several neuromodulation techniques have been utilized, with deep brain stimulation (DBS) exhibiting the strongest efficacy at around 50% reduction of tics on average across cohorts. However, the invasive nature of DBS remains a disincentive for its uptake, as well as the natural reduction in tic severity for many TS individuals as they enter adulthood. Less-invasive neuromodulation has also been explored, but efficacy remains limited. Given its effectiveness in TS, DBS provides the unique opportunity to record neural activity from deep brain structures, which has been used to investigate underlying pathophysiology and search for biomarkers of treatment response. These insights may guide strategies for less invasive neuromodulation. In this narrative review, we aim to discuss currently utilized neuromodulation therapies for the treatment of TS, as well as propose potential future strategies. Additionally, we discuss how to maximize progress in the field, including crucial multicenter data sharing, utilization of recording capabilities on DBS devices, correlation with the precise location of implanted electrodes, and harnessing pre-clinical studies for a more parameterized understanding of TS neuromodulation. These techniques will enable a clearer understanding of TS and the mechanisms behind successful treatment. This could lead to advanced therapies that improve the quality of life for individuals with TS.