Retinal venous sheathing in optic neuritis. Its significance for the pathogenesis of multiple sclerosis.

A systematic study of the frequency of retinal vascular abnormalities and cells in the media has been made in 50 patients presenting with acute optic neuritis. Abnormalities were found in 14 (fluorescein leakage in 10, perivenous sheathing in 6, cells in the vitreous in 6 and in the anterior chamber in 4; in 2 the cells in the media were seen without vascular changes). After a mean follow up of 3.5 years multiple sclerosis (MS) had developed in 8/14 patients with vascular abnormalities and/or evidence of inflammation and in 5/32 without; the difference is significant (P less than 0.02). The occurrence of perivenular abnormalities in a region free of myelin and oligodendrocytes provides evidence that the vascular changes in MS can occur independently of contiguous demyelination, and may be the primary event in the formation of a new lesion.