Neurologic complications of hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) involves the intravenous infusion of hematopoietic progenitor cells from an HLA-matched donor (allogeneic) or from the patient (autologous). Prior to HCT, the recipient is prepared (conditioning) with high-dose chemotherapy or radiotherapy (or both) to destroy defective bone marrow or residual cancer cells. After allogeneic HCT, there is the need for chronic immunosuppression to prevent graft rejection and graft-versus-host disease (GVHD). The frequency and type of neurologic complications depends on the type of HCT, the underlying disease, and the case ascertainment. In this review, the neurologic complications are presented according to the stage of HCT that they are most likely to occur: (1) conditioning-drug-related encephalopathies and seizures or complications secondary to medical procedures; (2) bone marrow depletion-metabolic and drug-related encephalopathies and seizures, septic cerebral infarctions, and hemorrhages; (3) chronic immunosuppression-infections by viruses and opportunistic organisms; and (4) late events-central nervous system (CNS) relapses of the original disease, neurologic complications of GVHD, and second neoplasms.