Brain Adapts Quickly to a Broken Arm

Shifts in the Brain Improve Skills So You're Not a Klutz for Long, Study Shows

Medically Reviewed by Louise Chang, MD on January 13, 2012

Jan. 16, 2012 -- Breaking an arm and wearing a sling or a cast is a real inconvenience, to say the least. When it's the arm you depend on to eat, write, dress, brush your teeth, bathe, and do most everything, well, that's when all the fun begins.

But Swiss researchers have discovered that the brain adjusts quickly to a broken limb. It doesn't take long -- perhaps a week or two -- before shifts in the brain occur so people can adapt to their new circumstances and be less clumsy in using their other arm.

A new study has shown that two weeks after a broken arm, there's an increase in the size of the brain areas needed to compensate for the injury, and a decrease in areas of the brain not being used while in a sling or cast. This rapid reorganization of the brain allows someone who is usually right-handed, for example, to transfer skills to the left hand while the hurt arm heals.

This finding is not only important for those with broken arms who temporarily need to rely on their less-used limb. It may also apply to people who are recovering from a stroke and working to regain lost motor skills.

"These results are especially interesting for rehabilitation therapy for people who've had strokes or other issues," researcher Nicolas Langer, MSc, says in a news release. He is a neuropsychology researcher at the University of Zurich in Switzerland.

The study is published in the journal Neurology.

How the Brain Adapts

In this small study, researchers asked 10 healthy people who were right-handed and broke a bone in their upper arm to have two MRIs. The first brain scan took place within two days of the injury and a second one occurred a little more than two weeks after getting a sling or cast.

Scientists tested how well the usual right-handers could move their left hand and use it to perform various tasks. Scans allowed them to see how certain regions of the brain had adapted to people having their dominant hand immobilized for at least 14 days.

Researchers observed that even within two weeks’ time, the volunteers were much better at using their left hand than they had been two days after the injury. Regions in the brain's left hemisphere linked with the use of the right hand had decreased in size.

Areas in the brain that improved skills in the left hand had increased in size, giving a person better movement and hand control in the uninjured arm. In other words, the sling or cast was doing its job of resting the limb so it could heal. And the brain had reorganized by forming new connections between brain cells to compensate for these changes.

In fact, the better an injured person could now do a usual task with his left hand, whether it was using a computer mouse or buttoning a shirt, the thicker the areas in the brain's right hemisphere, which control the task, had become.

"The findings highlight the capacity of the human brain to adapt rapidly to changing demands," write the researchers.