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

TLDR

Dystonia spans a spectrum from early‑onset genetically driven generalized forms to late‑onset sporadic task‑specific variants, with the latter thought to arise from repetitive motor tasks but lacking identified vulnerability traits. The study aimed to identify structural abnormalities indicative of preexisting dysfunction in dystonia using magnetoencephalography. Finger representations in primary sensory cortex were examined in 23 unilateral task‑specific dystonia patients and 20 controls via magnetoencephalography. All patients showed dramatic disorganization of the nondystonic hand representation, which correlated with dystonic limb severity, while abnormalities in the dystonic limb appeared only in the most severely affected and may reflect adaptive remapping in milder cases, indicating that nondystonic limb representations are endophenotypic traits of dystonia.

Abstract

Abstract Dystonia has a wide clinical spectrum from early‐onset generalized to late‐onset sporadic, task‐specific forms. The genetic origin of the former has been 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 magnetoencephalography, we looked for structural abnormalities reflecting a preexisting dysfunction. We studied finger representations of both hands in the primary sensory cortex, as compared in 23 patients with unilateral task‐specific dystonia and 20 control subjects. A dramatic disorganization of the nondystonic hand representation was found in all patients, and its amount paralleled the severity of the dystonic limb motor impairment. Abnormalities were also observed in the cortex coding the dystonic limb representation, but they were important only in the most severely affected patients. The abnormal cortical finger representations from the nondystonic limb appear to be endophenotypic traits of dystonia. 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.