A team of French researchers has linked abnormalities in certain neural pathways of the brain to the debilitating muscle disorder known as "writer's cramp."
The finding could lead to a better understanding of the neurological basis for the resulting loss of muscle control and coordination that characterises this difficult-to-diagnose disorder - also known as "hand dystonia." The condition can render a patient unable to write or even maintain a functional grip when trying to perform a simple task.
"These results demonstrate the presence of abnormalities in [brain] fibre tracts," that are located in areas known to be involved with writer's cramp, said study author Dr Stephane Lehericy, director of the Centre for NeuroImaging Research at Pitie-Salpetriere Hospital in Paris.
Linked to white brain matter
Lehericy explained that although prior research had already linked writer's cramp to problematic alterations in the grey matter in certain brain regions, the current investigation identified problems with the white matter of certain nerve pathways in brain areas that are responsible for generating motor commands.
Such white matter, explained Lehericy, "contains fibre bundles that convey information from one brain region to another, as well as to the spinal cord."
Lehericy and his team reported the findings in the April issue of the Archives of Neurology.
DTI scans on brain
To explore linkages between the disorder and the brain, the French team conducted high-tech diffusion-tenor magnetic resonance imaging (DTI) to scan for brain abnormalities among 26 right-handed writer's cramp patients, and 26 right-handed healthy participants.
Among the writer's cramp patients, the scans uncovered structural abnormalities in the white matter from the primary sensorimotor cortex region of the brain to below-cortex regions such as the thalamus. The observed abnormalities were not present among the healthy participants.
Such connections, the researchers noted, are typically key to the proper transference of motor coordination instructions from the brain to the spine, brain guidance that ultimately enables proper limb movement.
Dr Daniel Labovitz, director of the division of cerebral vascular disease at New York University's Langone Medical Centre, said the French researchers used "a very interesting technique to look at a very interesting problem."
"This is a solid piece of work," he said, "and a fascinating area of research that touches on issues that go far beyond writer's cramp alone, and has to do with a whole range of activity-related difficulties that clearly have to do with a problem with the brain."
"So this study builds on the little knowledge we have on an exceedingly rare and unusual issue; one for which we have virtually no treatment," Labovitz added. "No, this finding doesn't tell us what the brain changes mean exactly. But it does add incrementally and importantly to our understanding of the neurology underlying the problem." – (Alan Mozes/HealthDay News, April 2009)
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