Abstract
Focal hand dystonia (FHd) is a recalcitrant,
disabling movement disorder, characterized by
involuntary co-contractions of agonists and
antagonists, that can develop in patients who
overuse or misuse their hands. The aim of this
study was to document clinical neuromusculoskeletal
performance and somatosensory
responses (magnetoencephalography) in healthy
controls and in FHd subjects with mild versus
severe hand dystonia. The performance of
healthy subjects (n = 17) was significantly better
than that of FHd subjects (n = 17) on all clinical
parameters. Those with mild dystonia (n = 10)
demonstrated better musculoskeletal skills,
task-specific motor performance, and sensory
discrimination, but the performance of sensory
and fine motor tasks was slower than that of
patients with severe dystonia. In terms of
somatosensory evoked field responses (SEFs),
FHd subjects demonstrated a significant
difference in the location of the hand
representation on the x and y axes, lower
amplitude of SEFs integrated across latency,
and a higher ratio of mean SEF amplitude to
latency than the controls. Bilaterally,. those with
FHd (mild and severe) lacked progressive
sequencing of the digits from inferior to
superior. On the affected digits, subjects with
severe dystonia had a significantly higher ratio
of SEF amplitude to latency and a significantly
smaller mean volume of the cortical hand
representation than those with mild dystonia.
Severity of dystonia positively correlated with
the ratio of SEF mean amplitude to latency
(0.9029 affected, 0.8477 unaffected; p