Neurological complications of hematopoietic cell transplantation

Hematopoietic cell transplantation (HCT) involves the intravenous infusion of hematopoietic progenitor cells from the patient (autologous) or a human leukocyte antigen-matched donor (allogeneic). Before transplantation, the recipient undergoes a conditioning regimen with high-dose chemotherapy or radiotherapy (or both) to destroy a defective bone marrow or residual cancer cells. After allogenic HCT chronic immunosuppression is needed to prevent graft rejection and graft-versus-host disease. The frequency and type of neurological complication depends on the type of HCT, the underlying disease, and the case ascertainment. In this review the neurological 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 relapses of the original disease, neurological complications of graft versus host disease, and second neoplasms.