Abstract
Background.
In human upper-limb stroke, initial level of functional impairment or
corticospinal tract injury can accurately predict the degree of
poststroke recovery, independent of rehabilitation practices. This
proportional recovery rule implies that current rehabilitation practices
may play little or no role in brain repair, with recovery largely a
result of spontaneous biological recovery processes. Objective.
The present study sought to determine if similar biomarkers predict
recovery of poststroke function in rats, indicating that an endogenous
biological recovery process might be preserved across mammalian species.
Methods. Using a cohort of 593 male Sprague-Dawley rats, we
predicted poststroke change in pellet retrieval in the Montoya
staircase-reaching task based on initial impairment alone.
Stratification of the sample into “fitters” and “nonfitters” of the
proportional recovery rule using hierarchical cluster analysis allowed
identification of distinguishing characteristics of these subgroups.
Results.
Approximately 30% of subjects were identified as fitters of the rule.
These rats showed recovery in proportion to their initial level of
impairment of 66% (95% CI = 62%-70%). This interval overlaps with those
of multiple human clinical trials. A number of variables, including less
severe infarct volumes and initial poststroke impairments distinguished
fitters of the rule from nonfitters. Conclusions. These findings
suggest that proportional recovery is a cross-species phenomenon that
can be used to uncover biological mechanisms contributing to stroke
recovery.
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