Central nervous system complications after allogeneic hematopoietic stem cell transplantation: focusing on viral encephalitis and leukoencephalopathy

Abstract

 A variety of infectious agents (viral, fungal, or protozoan), cerebrovascular disease, immune-mediated mechanisms, metabolic abnormalities, drugs, or neoplasms can cause central nervous system (CNS) complications after allogeneic hematopoietic stem cell transplantation. CNS complications are frequently fatal, and their diagnosis and management can be challenging. HHV-6B encephalitis is a major cause of post-transplant viral encephalitis and should be considered as an important differential diagnosis, especially in cord blood transplant patients who develop CNS symptoms 2 to 6 weeks post-transplant. Reversible posterior encephalopathy syndrome (PRES) after allogeneic hematopoietic stem cell transplantation is primarily caused by calcineurin inhibitor-induced vascular endothelial cell damage. Myeloablative conditioning, immunologic activation, infections, and hypertension are risk factors for the development of PRES. The discontinuation of calcineurin inhibitors may improve neurologic symptoms but may exacerbate GVHD. Currently, the diagnosis of CNS infections caused by a variety of pathogens can be difficult with the currently available diagnostic tests. Comprehensive analysis using next-generation sequencing or other methods is expected to elucidate the full extent of CNS infections in allogeneic stem cell transplantation in the future.