Role of Frontal Cortex in the Pathophysiology of Gilles de la Tourette Syndrome (GTS)

Overview

Tourette's syndrome (TS) is a debilitating and severe syndrome whose pathophysiology remains unclear. In order to precise the cortical regions involved in the generation of tics, investigators will realize an electroencephalogram (EEG) recording in the frontal cortex of TS patients in ecological conditions (EEG-holter). Activity changes will be correlated with event markers of tics and neurovegetative parameters. Statistical analyses will be compared between epochs of EEG recording with tics and without tics. The aim is to define the cortical regions involved in the genesis of tics in order to consider new targets for cortical stimulation.

Gilles de la Tourette syndrome (GTS) is a childhood-onset disorder characterized by the presence of multiple motor tics and at least one vocal tic often associated with psychiatric co-morbidity. The expression of tics range from brief, recurrent and non-rhythmic motor or vocal actions (simple tics) to complex motor or vocal sequences (complex tics). The pathophysiology of tics is not yet fully understood. Recent imaging data suggest that the pattern of functional connectivity in cortico-basal ganglia networks is disrupted in GTS patients and could reflect a defect in brain maturation. However, regions involved in the immediate genesis of tics remains unknown since it is difficult to capture on line the cortical changes associated with tic generation using imaging techniques due to moving artefacts. Moreover, tics are much more frequent in everyday life conditions than in the artificial conditions of a laboratory. The aim is to study cortical activity changes occurring before tic occurrence by using long duration recording of encephalographic activity (EEG) in ecological conditions through Holter EEG techniques (24h recordings). Recordings will be performed in 15 patients with a severe form of Tourette's syndromes. EEG changes will be correlated to event markers, voluntary monitored by patients or automatically recorded (accelerometers for motor tics). EEG epoch centered on tics will be compared to similar epochs without tics. The occurrence of tics will also be correlated with neurovegetative markers of emotions such as RR interval ECG variability and skin resistivity changes. The ultimate goal of this project is to define a potential therapeutic target of tics for chronic cortical stimulation.