American Neurological Association (ANA)
Keywords: MULTIPLE SCLEROSIS OPTIC NEURITIS PLASTICITY
Description: There is evidence that the brain may respond to the ravages of multiple sclerosis (MS) by reorganizing its networks of connections, according to a report from the American Neurological Association's 124th annual meeting. 10/11/1999
EMBARGOED UNTIL **Monday, October 11, 11:00 AM ET**
American Neurological Association
BRAIN REORGANIZES IN MS PATIENTS
There is evidence that the brain may respond to the ravages of multiple sclerosis (MS) by reorganizing its networks of connections, according to a report from the American Neurological Association's 124th annual meeting, October 10 through 13 in Seattle.
Researchers from the Institute of Neurology at University College London, presented evidence that the brains of patients who suffered inflammation of the optic nerve, one of the most common sites involved in MS, reorganized so that sensory input from the damaged nerve fibers could still be correctly interpreted, allowing full recovery of vision.
Multiple sclerosis is a disorder of the nerve fibers of the brain, optic nerve, and spinal cord. In MS patients, scarring (sclerosis) replaces myelin, a substance that normally insulates the nerves and speeds electrical conduction through the fibers. Depending on which nerve fibers are hindered, patients can experience problems ranging from weakness and clumsiness to numbness, visual disturbances, and even emotional and intellectual changes.
Though the cause of MS is not known, circumstantial evidence has suggested it is an autoimmune disorder, wherein the immune system's defense mechanisms mistakenly destroy the myelin, perhaps in response to a virus or bacterium.
Some patients progress to severe debilitation and may die from the disease; others experience MS as cycles of relapse and remission. For about 50% of patients, the relapse/remission cycle includes optic neuritis, an inflammation of the nerves that transmit visual information from the retina to the brain.
"Patients with optic neuritis suffer temporary visual loss that usually recovers despite persistently abnormal conduction through the affected nerve, and even the degeneration of many nerve fibers. This may indicate that the brain compensates for the abnormal pattern of visual input to help restore vision," said Dr. David Werring, a researcher at the Institute of Neurology at University College and one of the authors of the report.
The researchers, led by Dr. Alan Thompson, tested their theory using the new brain scanning technique of functional magnetic resonance imaging (fMRI), which visualizes brain activity by measuring small changes in the concentration of oxygen in the blood. They compared the brains of patients who had recovered from optic neuritis to those of healthy controls.
As they had expected, the researchers found that stimulating either eye with a flashing light in controls activated only well-known visual areas at the back of the brain. However, when they presented the same flashing light to an eye that had previously been affected by optic neuritis, new areas outside (but connected to) these visual areas were activated.
"This result indicates that the brain has undergone a dramatic and enduring reorganization following disruption of its visual input by inflammatory damage. This type of reorganization has not previously been shown and could contribute to the recovery process after optic neuritis," said Werring.
If it can be confirmed that this reorganization actually helps the recovery process, something the authors hope to do by following patients from the onset of visual loss, these studies may help scientists develop and monitor rehabilitation strategies, not only for recovery from optic neuritis, but from other recurring manifestations of MS.