Primary demyelinating disorders are suggested by the following: Diffuse or multifocal deficits Sudden or subacute onset, particularly in young adults Onset within weeks of an infection or vaccination Deficits that wax and wane Symptoms suggesting a specific demyelinating disorder (eg, unexplained optic neuritis or internuclear ophthalmoplegia suggesting multiple sclerosis) Specific tests and treatment depend on the specific disorder.