Event-related functional MRI (fMRI) was used to study the neural basis of spontaneous motor and vocal tics in 10 patients with Tourette syndrome, at the National Institute of Neurological Disorders and Stroke, Bethesda, MD. fMRI activities were analyzed 2 seconds before and at tic onset, by synchronized video/audio recordings. Before the onset of tics, activated paralimbic areas included anterior cingulate and insular cortex, supplementary motor area and parietal operculum. At tic onset, fMRI activity occurred in sensorimotor areas including suprior parietal lobules and cerebellum. The paralimbic and sensory association areas involved in tic generation are similar to those implicated in movements triggered internally by unpleasant or emotional sensations, such as pain and itching. [1]
COMMENT. The authors postulate a limbic overdrive of the motor system and activation of sensorimotor areas underlying the pathophysiology of tic generation. The unpleasant urge and psychic tension that precede and trigger tics are similar to those of pain or itching, and involve the same paralimbic and sensory areas demonstrated by fMRI for tics. The distinction between the neural basis of involuntary motor tics and tics voluntarily acted out to bring momentary relief of the unpleasant sensation needs further study.