Ion channels and neuronal dysfunction in multiple sclerosis.

W hat causes the signs and symptoms of multiple sclerosis (MS)? It is almost axiomatic to regard MS as a demyelinating disorder in which axonal conduction block, caused by loss of myelin, produces clinical deficits. In addition, during the past few years, increased attention has focused on axonal degeneration in MS. The available evidence suggests that demyelination provides a structural correlate for relapsingremitting disease while axonal degeneration, which may be associated with atrophy of the brain and spinal cord, produces nonremitting deficits.