People who are severely afflicted by the problem -- defined as an involuntary sustained muscle contraction, or dystonia -- were found to have less brain tissue than their counterparts who did not have the complaint.

The deficits were observed in three areas of the brain linking senses and movement with the affected hand.

Writer's cramp tends to occur among people who repeatedly use the same muscles over a period of years.

For the study conducted at Salpetriere Hospital in Paris, France, investigators followed 30 people diagnosed with writer's cramp for approximately seven years. They used imaging to compare their brains to 30 people who did not have dystonia.

Three areas of the brain -- the cerebellum, the thalamus and the sensorimotor cortex -- had less gray matter in the study participants who had writer's cramp.

"It's not clear whether these abnormalities are a cause or a result of the disease," said study author Stephane Lehericy, MD, PhD, of Salpetriere Hospital.

"The fact that the brain abnormalities are in the areas that control the affected hand suggests that these differences are specific to this problem."

However, Lehericy also suggested the possibility that the repetitive movement associated with writer's cramp may have altered the brain structure.

"Studies have shown that people with no dystonia can experience brain changes due to learning new information, which supports this theory."