Case Study

Crippled arm leads to changes in brain.

Swiss scientists have shown that breaking your arm can affect your brain. It appears that immobilising the broken limb reduces the thickness of part of the cerebral cortex.

The study highlights how rapidly the brain can adapt in response to environmental changes, a phenomenon known as brain 'plasticity'.

Professor Lutz Jäncke and colleagues at the University of Zurich in Switzerland report their findings in the journal Neurology this week.

"This is the first human study to look at immobilised arms and actually see the plastic effect on the brain", says Jäncke.

Jäncke and his team investigated ten right-handed people who had broken their right arms. He scanned their brains using an MRI scanner within 48 hours of their accidents, just before their arms were immobilised by putting them in a sling or plaster cast.

Two other measurements were made at this stage: a fibre tract in the brain that sends commands to the arm was measured and the dexterity of their left hand assessed. Being right-handed, they would normally not use their left hand extensively.

The measurements were repeated about 16 days later, while their right arms were still immobilised.

The motor cortex on the left side of the brain controls the right arm, and the team found that its thickness had decreased significantly in response to the arm's lack of use. They also found thinning in the fibre tract.

"What we have found so far from studies on the plasticity of the brain is that we need to use it or lose it", says Jäncke.

As one might expect, left-hand dexterity also increased as patients got better at using their left hands for everyday tasks like eating and brushing their teeth. There were increases in the thickness of the brain cortex controlling the left hand too - but this was primarily in the pre-motor cortex, rather than the motor cortex itself.

"The pre-motor cortex is especially involved in doing something complicated", says Jäncke. "It installs and...