Intention tremor exaggerated by visually guided movement.

Intention tremor is caused by disorders of the cerebellar system. The kind of movement that exaggerates intention tremor has not yet been established. Thus, to investigate the contexts in which intention tremor is increased, I tested intention tremor patients as they performed two kinds of tasks, one involving sensory-guided movement and the other involving memory-guided movement. I report here on patients in whom intention tremor was exacerbated by sensory-guided movement and improved by memory-guided movement. Four patients were studied: 3 cases with hemorrhage in the thalamus or superior cerebellar pedunculus, and 1 case with multiple sclerosis (1 male and 3 females, mean age ± SD: 51.5 ± 13.1 years). Intention tremor interfered with skilful movement in all patients. Each had difficulty in writing, grasping a cup, and putting toothpaste on a toothbrush. Paradoxically, intention tremor sometimes decreased in all patients when they manipulated tools with their eyes