Abstract
Background.
Recent evidence from both monkey and human studies suggests that the
reticulospinal tract may contribute(weasel words are not useful to stroke survivors) to recovery of arm and hand function
after stroke. In this study, we evaluated a marker of reticulospinal
output in stroke survivors with varying degrees of motor recovery.
Methods.
We recruited 95 consecutive stroke patients presenting 6 months to 12
years after their index stroke, and 19 heathy control subjects. Subjects
were asked to respond to a light flash with a rapid wrist flexion; at
random, the flash was paired with either a quiet or loud (startling)
sound. The mean difference in electromyogram response time after flash
with quiet sound compared with flash with loud sound measured the
StartReact effect. Upper limb function was assessed by the Action
Research Arm Test (ARAT), spasticity was graded using the Modified
Ashworth Scale (MAS) and active wrist angular movement using an
electrogoniometer.
Results. StartReact was significantly larger in stroke patients than healthy participants (78.4 vs 45.0 ms, P
< .005). StartReact showed a significant negative correlation with
the ARAT score and degree of active wrist movement. The StartReact
effect was significantly larger in patients with higher spasticity
scores.
Conclusion. We speculate that in some patients with
severe damage to their corticospinal tract, recovery led to
strengthening of reticulospinal connections and an enhanced StartReact
effect, but this did not occur for patients with milder impairment who
could use surviving corticospinal connections to mediate recovery.
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