Brain Activity Associated With Tics in Patients With Tourette Syndrome

OBJECTIVES: This study will examine the spatiotemporal dynamics of sensory tics in patients with Tourette syndrome (TS). We will also investigate the possible existence of a sensory gating problem. By investigating somatosensory evoked responses from stimulation of the trigeminal nerve (tSERs) on affected versus unaffected sides of the face, we hope to identify differences in the SER waveforms that suggest sensory abnormalities. We will use a series of short trains of stimulations on the affected side to examine habituation, subsequently performing a time- frequency analysis to seek indicators of decreased sensory gating. This study will examine, specifically: Whether the cortical neurocircuitry involved in the elicitation of tSERs differs in patients with tic disorders from controls. If SERs differ in a sensory tic facial region of patients, compared to the same spot on an unaffected side of the face. Whether in controls and patients with sensory tics on both sides of their body, tSERs on both sides of the face are symmetrical. If there is a lack of habituation in tic patients to tSERs in a short-train click paradigm, compared to controls. The location for sources of abnormalities in either paradigm. STUDY POPULATION: Twenty patients and 10 control subjects will be studied. Subjects can be of any race, gender, handedness, or age between 14 and 65 years. DESIGN: This study will compare tSERs in normal volunteers to those in TS patients. Patients with bilateral sensory tics will be contrasted with those who have unilateral sensory tics, comparing power of the response at latencies on affected versus unaffected sides. Subjects will be seated in the MEG and instructed to "feel the delivered sensation, and try not to tic for seventy seconds, without counting". The trigeminal nerve will be electrically stimulated at 0.25 Hz for 30 seconds, which will be followed by head localization and subsequent rest for tic release. To evaluate sensory gating, the design is similar except the trigeminal stimulation will occur in short trains. Patients will be surveyed to determine if the instructions intensified sensory tics. OUTCOME MEASURES: We will compare the power of averaged tSERs at latencies, comparing face sides in patients and comparing patients' active face side with controls' dominant face side. The power of frequency components at latencies will be considered. We will locate the sources of differential tSER activity.