Researchers at the FDA, Silver Spring, MD; Department of Neurology, University of Pittsburgh Medical School, PA; National Institute of Mental Health, NIH, Bethesda, MD; and other centers used a PET study to assess the involvement of the GABA-ergic system in 11 adult Tourette syndrome patients compared to 11 healthy controls. Structural MRI scans provided an anatomical framework for the PET data analysis. Tourette patients had decreased binding of GABA receptors in the ventral striatum, globus pallidus, thalamus, amygdala and right insula. Increased binding of GABA receptors was found in the bilateral substantia nigra, left periaqueductal grey, right posterior cingulate cortex and bilateral cerebellum. These findings are consistent with the hypothesis that basal ganglia and thalamus circuits are disinhibited in Tourette syndrome. 
COMMENT. The global functional disorganization of cortico-basal ganglia networks found in patients with TS agrees with the hypothesis of a functional immaturity of these circuits, contributing to a clinical heterogeneity of TS, including association with ADHD and OCD. Severity of OCD is correlated with functional abnormalities in associative and limbic networks, orbito-frontal and prefrontal dorsolateral cortices. 
Omega-3 Fatty Acids and TS. A double-blind, placebo-controlled, add-on trial of omega-3 FA in 33 children and adolescents with TS showed no significant reduction in frequency of tics, but significantly more subjects on omega-3 were benefited by a reduction in tic severity and related impairments. The rate of ADHD comorbidity was significantly lower in the omega-3 group than placebo. Mean end dose of omega-3 was 4074 mg/d and much higher than that generally advocated for ADHD patients (600 mg/d).