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| Magnetic stimulation safely improves motor function after stroke |
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29 June 2006
As a rehabilitation technique for stroke, repetitive transcranial magnetic stimulation (rTMS) can slow the hyperactivity seen in the unaffected hemisphere, resulting in an improvement in motor function. The findings indicate that the magnitude and duration of motor benefits can be safely increased through the use of more than one rTMS session. With five consecutive sessions, sustained improvements in motor function were noted over the 2-week study period.
After a stroke, lead author Dr Felipe Fregni, from Harvard Medical School in Boston, explains, the unaffected hemisphere attempts to recover the function lost by the affected hemisphere, but in so doing inhibitory signals are sent to the affected hemisphere and this may impair functional recovery. Transcranial magnetic stimulation is thought to work by reducing the frequency of these inhibitory signals.
The study involved 15 patients with chronic stroke who were randomised to undergo active or sham rTMS, applied to the unaffected hemisphere. Motor function and corticospinal excitability were assessed at baseline, during, and after treatment by a rater blinded to the assigned treatment. Active, but not sham, rTMS was associated with significant improvements in motor function in the affected hand over the study period. At the same time, corticospinal excitability decreased in the unaffected hemisphere, while it increased in the affected hemisphere.
In the simple-reaction-time task, patients were, on average, 30% faster than at baseline after five days of treatment, and this effect lasted for 2 weeks. Patients were, on average, 10%, 20%, 27%, and 30% faster on days two, three, four, and five, respectively. And this improvement in motor function was significant when compared to sham stimulation. There was no evidence that five sessions of rTMS adversely affected cognitive performance or promoted seizures.
The researchers call for larger studies to replicate their findings and to explore other stimulation parameters that may enhance motor function further.
Reference:
Stroke 2006; Epub ahead of print.
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