Neurologic Complications of Organ Transplantation

Over the past four decades, remarkable advances have been made in the field of organ transplantation. Improved surgical techniques and perioperative care have reduced the mortality and morbidity of many organ transplant procedures to acceptable levels. The creation of national and international organ registries has resulted in a more efficient system for organ procurement and use. Advances in immunology and the introduction of more potent immunomodulating agents have led to doubling of survival rates for those with transplanted grafts. Unfortunately, a high rate of neurologic complications associated with organ transplantation persists. Cerebral embolization, hypoxia, and bleeding remain frequent after heart and lung transplantation. Prolonged thrombocytopenia associated with bone marrow transplantation still leads to catastrophic cerebral hemorrhage. Although the period of neutropenia following bone marrow transplantation has been reduced by the use of growth factors, and the routine use of potent prophylactic antibiotic and antiviral agents has reduced the incidence of infection, unusual or resistant central nervous system (CNS) infections continues to arise, often creating difficult treatment choices. Furthermore, the more effective classes of immunosuppressants may have direct toxic effects on the nervous system. The major challenge for the future is to develop agents and strategies for management that can effect selective tolerance to the donated organ without paralyzing the immune system's ability to fight infection. Such agents must also have limited or no toxicity to the nervous and other organ systems. The observations by Starzl on the existence of leukocyte chimerism years after transplantation suggest that understanding and building on this natural phenomenon may hold promise for solving major problems in the field of organ transplantation.