Dissociated foveal and parafoveal visual evoked responses in subacute combined degeneration

In four patients with subacute combined degeneration, clinically silent involvement of the visual pathways was demonstrated by visual evoked responses following selective foveal and parafoveal stimulation. The characteristic distribution of the lesion is different from that generally found in patients with multiple sclerosis, and affects slow- and fast-conducting fibers in an opposite manner.