Active multiple sclerosis. Enhanced computerized tomographic imaging of lesions and the effect of corticosteroids.

Computerized axial transmission tomography (CT) of the brain is useful for imaging lesions in multiple sclerosis (MS). Active demyelination may be demonstrated with CT contrast enhancement (CTE) as regions of increased x-ray density. We report a series of patients with active MS who typify these changes. Corticosteroid therapy reduces the intensity of this phenomenon presumably by reestablishing the integrity of the blood-brain barrier; if corticosteroid therapy is instituted prior to the CT contrast study, the focal enhancement may be obscured. A transient vascular permeability defect is the basis for CTE during the acute exacerbation in MS. The possibility of MS must be kept in mind when one or more foci of increased density occur in the absence of mass effect during CTE. Appreciation of these features may prevent misdiagnosis.