Aside from correcting hypoperfusion, it is possible to improve oxygen delivery to the CNS by increasing the hematocrit, and it is interesting in this context that therapy with erythropoietin (EPO; which has a range of effects but most notably boosts red cell production) improved outcome in both a pilot study in progressive MS and a phase II trial in optic neuritis.36, 37. This evidence concerns the gene EPO and myeloid sarcoma.