Quantitative study of spontaneous eye blinks and eye tics in Gilles de la Tourette's syndrome.

Spontaneous eye blink rate and frequency of eye tics were studied in nine Tourette patients during periods of rest, conversation, and video watching. In comparison with controls, the Tourette patients showed a significantly higher blink rate during rest and video watching. Conversation induced a significant increase in blink rate in the control group, but not in the Tourette patients, whereas video watching significantly increased blink rate in both groups. The frequency of eye tics showed a significant decrease during conversation and increased significantly during video watching in Tourette patients. In five patients, a significant positive correlation between blink rate and eye tic frequency was found, whereas one patient showed a significant negative correlation. Our results show that, even though some of our patients were on neuroleptic treatment, blink rate was about twofold to threefold increased versus healthy controls, suggesting increased central dopaminergic activity. Furthermore, these first quantitative data illustrate task specific effects on eye tic frequency and the complexity of their relation with eye blinks.