Stereotactic selective Vo-complex thalamotomy in a patient with dystonic writer's cramp

In the last decade, Sheehy and Marsden¹ proposed that writer's cramp is a physical dystonic disorder, and classified the illness into simple and dystonic type, depending on whether or not the symptoms appear only during writing. The pathophysiology of writer's cramp has been under dispute.² Writer's cramp may be a disorder of motor subroutines possibly retained by the "set-related" neurons in the motor cortices and their connections to the basal ganglia, i.e., the cortex-basal ganglia-thalamus-cortex motor loop.² We report a patient with dystonic writer's cramp treated by successfully selective Vo-complex thalamotomy. The term Vo-complex refers to the combination of the ventralis oralis posterior nucleus (Vop) and ventralis oralis anterior nucleus (Voa) of the thalamus.

Case report. In 1991, an 18-year-old woman student at a high school noticed that her right hand became stiff when she wrote in a tense atmosphere. To write, she had to hold the pen tightly with exaggerated finger grip. The severity of her writing disability gradually progressed, and about 2 years later she could not write with her right hand at all; she taught herself to write with her left hand. From the beginning of 1995, the muscle cramps affected other manual tasks, such as the ability to handle a pair of chopsticks or a cup and saucer, and to put on lipstick. She consulted with a neurologist and was diagnosed as having dystonic writer's cramp. Medical and family history were not contributory. At first, the muscle cramp was markedly improved by medication including trihexyphenidyl (6.0 mg/day) and clonazepam(1.5 …