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Tourette syndrome (TS) is a complex childhood-onset neuropsychiatric disorder characterized by multiple motor tics, plus one or more vocal tics, lasting longer than 1 year. The prevalence of TS in childhood is estimated at 0.3–0.9%, and overall TS has a favorable prognosis. About one third of children with TS will experience a significant decrease in tics during adolescence, and another third of children will become completely tic free. Yet a small proportion of patients do not experience this remission. There is no cure for TS, and treatment aims to reduce or alleviate tics and other comorbid symptoms. Behavioral therapy and pharmacological treatment may provide relief, but some patients remain refractory or experience unbearable side effects. For those patients, deep brain stimulation (DBS) can be considered. The first TS patient was treated with DBS of the thalamus in 1999; since then, approximately 270 patients have been operated. A key factor in attaining optimal results from this surgery is target selection, a topic still under debate due to the complex clinical profile presented by TS patients. Nine separate brain areas have been targeted so far: the medial part of the thalamus (three different areas), the internal globus pallidus (GPi) (anterior and posterior part), the external globus pallidus (GPe), the nucleus accumbens (NA), the anterior limb of the internal capsule (ALIC), and the subthalamic nucleus (STN). Interfering with DBS at the level of one of the main output or relay stations of the basal ganglia seems to result in clinical benefits in refractory TS patients. Overall, DBS results in a significant short-term improvement of 53% on the Yale Global Tic Severity Scale (YGTSS) on all targets. The degree of tic improvement appears to be most robust for the thalamic and the GPi targets. Further research should provide more clarity in selection of the optimal stimulation target, stimulation parameters, and the effectiveness of this treatment. |
