Graft versus host disease (GvHD) is a common and often troublesome complication of allogeneic bone marrow transplantation. Neurological complications usually involve the peripheral nervous system and muscle, but the central nervous system may be affected. When an optic neuropathy develops, it is often difficult to determine the cause quickly; infective complications and drug toxicity may have arisen, but an inflammatory disorder due to GvHD should also be considered, particularly since treatment with steroids and immune suppression may improve the outcome significantly. This brief case report shows how this may be the case and reviews our current understanding of the pathophysiology and treatment of the disorder within the nervous system.