CEREBRAL AND CEREBELLAR ACTIVATION IN CORRELATION TO THE ACTION-INDUCED DYSTONIA IN WRITERS CRAMP

The pattern of brain perfusion of four patients with writer's cramp an d four control subjects were examined using positron emission tomograp hy scans after [O-15] butanol injections. Each subject was scanned 12 times to cover three repetitions of four different motor tasks with th e right hand. Drawing of horizontal lines and variable durations of th e writing of a prelearned text were performed in a pseudorandom order, the latter task commencing either simultaneously with or 30 sec or 12 0 sec before the tracer injection. The perceived difficulty and signs of dystonia progressed in correlation to the duration of writing. Stat istical parametric maps were calculated to test hypotheses of regional specific effects dependent on the performed motor tasks. The patients with writer's cramp had progressively increased activity in the left primary sensorimotor and premotor cortices, the left thalamus, and the cerebellum with a right-side predominance in correlation to the durat ion of writing.The regions with activity increases thus corresponded t o a cerebrocerebellar motor circuit. The duration of writing correlate d to a progressive reduction of activity in the patients' left suprama rginal and angular gyri (Brodmann areas 40 and 39) and an inferior par t of the left temporal lobe (area 20). The control subjects had neithe r a significant increase or decrease of activity in correlation to the duration of writing. Group-specific differences were confirmed statis tically in split-plot interaction analyses.