Effective behavioral treatment of focal hand dystonia in musicians alters somatosensory cortical organization

Abstract

New perspectives in neurorehabilitation suggest that behavioral treatments of movement disorders may modify the functional organization of central somatosensory neural networks. On the basis of the assumption that use-dependent reorganization in these networks contributes to the fundamental abnormalities seen in focal dystonia, we treated 10 affected musicians and measured the concomitant somatosensory changes by using whole-head magnetoencephalography. We found that effective treatment, using the method of sensory motor retuning, leads to alterations in the functional organization of the somatosensory cortex. Specifically, before treatment, somatosensory relationships of the individual fingers differ between the affected and unaffected hands, whereas after treatment, finger representations contralateral to the dystonic side become more similar to the less-affected side. Further, somatosensory finger representations are ordered more according to homuncular principles after treatment. In addition, the observed physiologic changes correlated with behavioral data. These results confirm that plastic changes in parallel with emergent neurological dysfunction may be reversed by context-specific, intensive training-based remediation.

Fig. 1.

Dexterity displacement device. Shown are pre- and posttreatment segments of the movement slopes of right D3 (RD3) and left D3 (LD3) of one patient during the performance of a trill-like task at a fast and free selected velocity. Pretreatment, the recorded movements of the dystonic finger (RD3) were uneven and uncontrolled (upper RD3 profile) compared with the movements of the homologous LD3 (upper LD3 profile), which served as a control finger. These differences are no longer present posttreatment (lower LD3 and RD3 profiles, respectively). For simplicity, only D4 and D5 are depicted in the photographs.

Fig. 2.

Mean Euclidean distances of the dystonic (treated) and nondystonic hands pre- and posttreatment. The indices of functional organization in the hemispheres were deviant before but similar after the treatment.

Fig. 3.

Euclidean distance arrangement for the distances D1–D2, D2–D5, and D1–D5 for the dystonic and nondystonic hands. Posttreatment, the normal arrangement was fitted in both hands (normal arrangement D1–D2 < D2–D5 < D1–D5).