Progressive disability in people with multiple sclerosis (MS) is largely caused by a slowly progressive degeneration of nerve fibers in brain and spinal cord. The MS research team of the Center for Neurosciences (www.c4n.be) VUB describes in the Proceedings of the National Academy of Sciences (18 March 2013) a new disease mechanism in MS. They found that astrocytes (support cells of the nervous system) produce a substance (endothelin-1) which makes blood vessels to contract, leading to a decreased blood flow in the brain. Reduced blood flow in the brains of animals leads to a degeneration of nerve fibers. Cerebral blood flow in persons with MS could be corrected by the administration of an endothelin-1 antagonist, which opens the door to new types of treatment for the disease.