Writer's Cramp May Be Tied to Brain Abnormalities

Mar. 23 -- TUESDAY, July 24 (HealthDay News) -- Could writer's cramp be all in your mind?

New research suggests just that, with French scientists saying they've identified structural abnormalities in the brains of people prone to the painful condition. The abnormalities consist of less brain tissue in areas that govern motor skills, movement and sensory functioning.

"It's always nice to know as much as you can about something before you devise a treatment," said Dr. Tom Swift, past president of the American Academy of Neurology and professor emeritus and former chairman of the department of neurology at the Medical College of Georgia. "With a lot of dystonias, for a long time it was thought there weren't any anatomical abnormalities, even for severe dystonias. Using newer [imaging] techniques with higher resolutions, there are some areas that show abnormalities, but they're very subtle."

Writer's cramp is a dystonia, or a movement disorder that causes involuntary contractions of the muscles. The condition refers to involuntary muscle contractions of the fingers, hand or arm while writing or performing other manual tasks. It often occurs in people who have used the same muscles repeatedly for years. As a result, writing can become a painful activity, and written work can become far less legible, according to the Dystonia Society.

In one quarter of cases, the condition affects both hands. Overall, writer's cramp affects three to seven of every 100,000 people, a relatively small proportion, but it can negatively affect work, self-esteem and social life, the study authors said.

"In fully developed writer's cramp, the fingers grip the pen very tightly, and the arm drags down to the right lower corner of the page. It's pretty serious," Swift said. "Even typing can produce a similar kind of thing."

The disorder is complicated and not well understood, Swift said. "There are so many inputs that go into producing a smooth movement, it becomes one of the most complicated things in neurophysiology to figure out how the system works," he explained.

But there are effective treatments. They include injections of Botox, or Botulinum toxin, a protein complex produced by the bacterium Clostridium botulinum that contains the same toxin that causes food poisoning. Sterile, purified botulin toxin in small doses blocks the release of acetylcholine, a chemical produced by nerve cells that signals muscles to contract.

For the new study, published in the July 24 issue of Neurology, the researchers produced brain images of 30 people who had had writer's cramp for an average of seven years. The images were then compared with brain images of healthy people.

The participants with writer's cramp had less grey matter in three areas of the brain: the cerebellum, the thalamus and the sensorimotor cortex -- areas that control the affected hand.

The researchers now face a chicken-and-egg situation, because it's not clear whether the abnormalities are a cause or effect of writer's cramp.

According to Swift, the work also needs to be confirmed by independent researchers.

The study's author agreed that more research is needed.

"It is reassuring to know that physicians and researchers can identify the brain abnormalities underlying the trouble, even though yet there is no therapeutic consequences," said Dr. Stephane Lehericy, senior author of the study and head of the Center for Neuroimaging Research at Groupe Hospitalier Pitie-Salpetriere in Paris, France.

"Our findings show that several brain structures are abnormal in writer's cramp, including the cerebellum, suggesting that the cerebellum plays a role in the disease," Lehericy said. "The role of this structure in the disease will probably be investigated in more detail in animal models (some animal models have abnormalities in the cerebellum) and also in humans. Moreover, cerebellum is involved in motor control and scaling of fine movements and this may influence the way rehabilitation will be performed," he said.

More information

The Dystonia Society has more on writer's cramp.

SOURCES: Tom Swift, M.D., past president, American Academy of Neurology, and professor emeritus and former chairman, department of neurology, Medical College of Georgia, Augusta; Stephane Lehericy, M.D., Ph.D., head, Center for Neuroimaging Research, Groupe Hospitalier Pitie-Salpetriere, Paris, France; July 24, 2007, Neurology