Human brain mapping in dystonia reveals both endophenotypic traits and adaptive reorganization

Dystonia has a wide clinical spectrum from early-onset generalized to late- onset sporadic, task-specific forms. The genetic origin of the former has b een clearly established. A critical role of repetitive skilled motor tasks has been put forward for the latter, while underlying vulnerability traits are still being searched for. Using magneto encephalography, we looked for structural abnormalities reflecting a preexisting dysfunction. We studied f inger representations of both hands in the primary sensory cortex, as compa red in 23 patients with unilateral task-specific dystonia and 20 control su bjects. A dramatic disorganization of the nondystonic hand representation w as found in all patients, and its amount paralleled the severity of the dys tonic limb motor impairment. Abnormalities were also observed in the cortex coding the dystonic limb representation, but they were important only in t he most severely affected patients. The abnormal cortical finger representa tions from the nondystonic limb appear to be endophenotypic traits of dysto nia. That finger representations from the dystonic limb were almost normal for the less severely affected patients may be due to intrinsic beneficial remapping in reaction against the primary disorder.