CASE

Multiple Sclerosis: Myelin and Conduction Velocity

Meg Newton is a 32-year-old assistant at a horse-breeding farm in Virginia. She feeds, grooms, and exercises the horses. At age 27, she had her first episode of blurred vision. She was having trouble reading the newspaper and the fine print on labels. She had made an appointment with an optometrist, but when her vision cleared on its own, she was relieved and canceled the appointment. Ten months later, the blurred vision returned, this time with other symptoms that could not be ignored. She had double vision and a pins and needles feeling and severe weakness in her legs. She was even too weak to walk the horses to pasture. Meg was referred to a neurologist, who ordered a series of tests. Magnetic resonance imaging (MRI) of the brain showed lesions typical of multiple sclerosis. Visual-evoked potentials had a prolonged latency that was consistent with decreased nerve conduction velocity. Since the diagnosis, Meg has had two relapses, and she is currently being treated with interferon beta.