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16-01-2012 | Physical rehabilitation | Article

Rapid brain changes help body compensate for injured, immobilized arm


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MedWire News: Research shows that the brain helps the body to compensate for dominant arm injury and immobilization by increasing the size of areas of the brain controlling fine movement of the nondominant arm.

The study, which is published in Neurology, not only demonstrates that cortical thickness and fractional anisotropy (FA) within the corticospinal tract are increased in the side of the brain controlling the nondominant arm, but also shows that the size of these areas on the side of the brain controlling the injured arm decreased after a short period of limb immobilization.

"These results are especially interesting for rehabilitation therapy for people who've had strokes or other issues," said study author Nicolas Langer (University of Zurich, Switzerland) in a press statement.

"One type of therapy restrains the unaffected, or 'good,' arm to strengthen the affected arm and help the brain learn new pathways. This study shows that there are both positive and negative effects of this type of treatment."

Little research has covered the effects of decreased sensory input and motor output of different limbs on the human brain. To investigate further, Langer and team recruited 10 right-handed individuals with an injury of the right arm requiring immobilization for at least 14 days.

The participants underwent magnetic resonance imaging (MRI) at a mean of 48 hours and 16 days post injury. At the time of the second scan, the patients' injured limbs had been immobilized for at least 14 days.

Using the MRI images, the researchers measured cortical thickness of sensorimotor regions and FA of the corticospinal tracts on both the right and left sides of the brain; areas responsible for the control of fine motor movements.

The results from the MRI scans showed that the patients had significant decreases in these areas on the left side of the brain (responsible for movement in the right side of the body) following 16 days of arm immobilization.

Of note, the motor skill of the uninjured hand improved during immobilization of the injured arm, which the investigators attribute to increases in cortical thickness and FA on the right side of the brain.

"These structural changes in the brain are associated with skill transfer from the right hand to the left hand," said Langer, who explained that it is currently unknown how long these changes may last for.

"Further studies should examine whether using a restraint for stroke patients is really a necessity for improving arm and hand movement," he said.

"Our results also support the current trauma surgery guidelines stating that an injured arm or leg should be immobilized 'as short as possible, as long as necessary.' "

By Helen Albert

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