PARIS (UPI) -- The brains of people with bad writer's cramp are different from normal brains, says a French study, but it is unclear on which condition came first.

Stephane Lehericy and his colleagues at Salpetriere Hospital in Paris found that the 30 people they studied who had experienced writer's cramp (but no other forms of dystonia) for an average of seven years also had less gray matter in their cerebellum, thalamus, and sensorimotor cortex on the side of their brains connected to the hand that cramped. ""It's not clear whether these abnormalities are a cause or a result of the disease,"" said Lehericy. ""The fact that the brain abnormalities are in the areas that control the affected hand suggested that these differences are specific to this problem; but another theory is that the brain structure changed and adapted as a result of the sustained repetitive movement. Studies have shown that people with no dystonia can experience brain changes due to learning new information, which supports this theory."" Writer's cramp is a form of involuntary, sustained muscle contraction called dystonia. The study appears in the July 24 issue of the journal Neurology