The origin of cerebrospinal fluid procoagulant activity.

G RAEBER AND STUART’ reported an increase in procoagulant activity in the cerebrospinal fluid (CSF) of children with acute lymphoblastic leukemia (ALL) following prophylactic central ncrvous system (CNS) treatment with cranial radiation and intrathecal methotrexate. They postulated that the shortening of the plasma recalcification time (PRT) reflected the presence of brain phospholipid released into the CSF by demyelination. The purpose of the study reported here was to examine in more detail the phenomenon they described. We offer an alternative postulate for the origin of “CSF procoagulant.”