[P2-25] MRI Volumetry of Hippocampus in Two Cases with HHV-6B-asscoiated Encephalopathy after Hematopoietic Stem Cell Transplantation
Reactivation of human herpesvirus-6 (HHV-6) is common after hematopoietic stem cell transplantation (HSCT), and is associated with post-transplant acute limbic encephalitis (PALE) in adult patients. Although PALE is rare in children, it has been suggested that HHV-6B reactivation might be involved in memory impairment in pediatric HSCT recipients. Therefore, we conducted MRI volumetry of the hippocampus before and after HSCT to evaluate an association between hippocampal volume and HHV-6B reactivation. For the pilot study, we examined two pediatric recipients with encephalopathy at the time of HHV-6B reactivation. We performed hippocampal volumetric analysis using Workstation (AZE Virtual Place Raijin). Case 1 had PRES 2 weeks after transplant. Although high amount of HHV-6B DNA was detected in blood, no viral DNA was detected in cerebrospinal fluid (CSF). Hippocampal volume after the HSCT was decreased remarkably (before: R 3240mm³/ L 2610mm³, after: R 2000 mm³/ L 1620mm³). Case 2 had PRES 3 weeks after transplant. High copies of HHV-6B DNA were detected in not only blood but also CSF. Therefore, this case was diagnosed as HHV-6B encephalitis, and was treated by ganciclovir (GCV). No remarkable change in hippocampal volume was demonstrated after the HSCT (before: R 2640mm³ / L 2620mm³, after: R 2840mm³/ L 2530mm³). Mechanism for reduction of hippocampal volume observed in case 1 is unclear. GCV treatment may prevent brain tissue damage in case 2. Analysis of large number of cases is now underway to investigate the influence of HHV-6B reactivation on hippocampal damage in pediatric HSCT recipients.