[Multiple sclerosis].
Multiple sclerosis is a chronic inflammatory disease of the central nervous system which affects young and middle-aged adults. The clinical symptoms and course vary considerably; most patients experience a relapsing-remittent course which may become secondary progressive, a benign course with a favourable prognosis is seen in 30-40%. 10-15% experience a primary progressive course, with a less favourable prognosis. Magnetic resonance imaging, MRI, has become the most important paraclinic investigation and MRI with paramagnetic contrast enhancement reveals "subclinical" disease activity. Demyelination is caused by phagocytosis of microglial cells which appear to be activated by cytokines produced by T helper cells. A delayed type autoimmune response to myelin antigens is probably involved, initiated by a viral infection. Immunosuppressive treatment, corticosteroids and interferons have been shown to affect the MRI behaviour, and reduce the frequency of relapse. The effect on the natural course of the disease has been less convincing and no treatment will reverse long standing neurological dysfunction.