Ampyra (dalfampridine) is a potassium-channel antagonist, with a mechanism-of-action to improve nerve conduction in demyelinated axons, resulting in an electrophysiologic and clinical benefit.10-22 Demyelinated axons within the anterior visual pathway would be a prime and ideal target to study the effects of Ampyra. In fact, Stefoski et al demonstrated visual function benefit in an open-label study of IV 4-aminopyridine in 12 subjects.21 The optic nerves are a well-defined white-matter tract, commonly affected in MS, and with clear clinical outcome measures. In addition, visual evoked potentials (VEPs) can be included within the study design as a secondary endpoint, to confirm improved nerve conduction. Because VEPs are such a precise, reliable, and accepted measure of demyelination, the anterior visual pathway is the ideal in vivo human system to study the electro-physiologic effects of a therapeutic such as Ampyra.