Evidence suggests a time-limited window after stroke, during which the greatest gains can be made in rehabilitation. A recent review by Murphy and Corbett, published in the journal Nature Reviews, looked at animal models of stroke recovery in order to understand how to make the most of this opportunity.
The review looked at studies showing that genes responsible for early growth in the brain are also activated for a brief time after stroke. The activation of these genes causes the brain to reorganise itself in a similar way to a child's during development. If this is correct then it is important to target rehabilitation so that it happens within the period of heightened 'neuroplasticity'.
Studies on rats have shown the importance of early intervention in capitalising on this process. The rats were exposed to an enriched environment, designed to enhance motor function, at five, 14 or 30 days after stroke. Animals given the early intervention displayed significant recovery, whereas those given treatment after 30 days exhibited little or no improvement.
These results provide strong evidence that therapy should be provided as early as possible. This does not mean that rehabilitation is ineffective after a certain time period. Many stroke patients continue to improve many years after the original injury. However, the potential for plasticity does diminish over time and the challenge is to find ways of widening this window of opportunity.
Administering certain proteins has been shown to initiate plasticity in the visual system of adult animals and promote recovery after spinal cord injury. Whether such treatment could have applications for stroke recovery could be a subject of future research.
Reference
Murphy TH & Corbett D (2009) Plasticity during stroke recovery: from synapse to behaviour. Nature Reviews, 10: 861-872.
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