This study investigates the role of sphingosylphosphorylcholine (SPC) in the mechanisms underlying cerebral vasospasm after subarachnoid hemorrhage (SAH). The levels of SPC were measured in cerebrospinal fluid (CSF) of patients with SAH and also in an experimental canine model. CSF samples were collected from I I patients with SAH, and from dogs that had received an injection of SPC into the cisterna magna to examine SPC kinetics in the CSF. SPC was assayed using solid-phase extraction and triple quadrupole mass spectrometry. The SPC concentrations in SAH patients on days 3, 8, and 14 after the onset of SAH were significantly higher than those in normal CSF In the canine model, rapid dilution of SPC in CSF was observed. In combination with data from previous studies, these results Suggest that SPC is involved in the development of cerebral vasospasm. Rapid dilution of SPC in CSF suggests that SPC is released into CSF at higher concentrations than those measured in the present study. (C) 2009 Elsevier Ltd. All rights reserved.