“…Historically, it was considered that the CNS could not be affected by GVHD. However, over the last decade, preclinical data (Belle et al, 2017;Hartrampf et al, 2013;Sostak et al, 2004) and clinical case reports (Harvey et al, 2014;Openshaw et al, 1995;Sostak et al, 2010;Stefanou and Bischof, 2017;Voss and Bischof, 2010) progressively accumulated and CNS-GVHD is now becoming recognized as a true entity (Armstrong et al, 1997;Belle et al, 2017;Grauer et al, 2010;Hartrampf et al, 2013;Harvey et al, 2014;Maffini et al, 2017;Openshaw et al, 1995;Rouah et al, 1988;Ruggiu et al, 2017;Sostak et al, 2004;Sostak et al, 2010;Stefanou and Bischof, 2017;Voss and Bischof, 2010). Nevertheless, the diagnosis of CNS-GVHD still remains difficult mainly because of the low prevalence of the disease, confounding factors and heterogeneous clinical presentations.…”