- CSF flow: Patients must be willing to have a CSF flow study to determine whether or not they will receive intrathecal chemotherapy. Patients without a VP or VA shunt must be willing to have an Ommaya reservoir if their CSF flow study does not show any evidence of obstruction to or compartmentalization of flow. Patients with obstruction to or compartmentalization of CSF flow on their initial flow study must be willing to have a repeat flow performed within the initial 10 weeks of induction therapy, ideally during weeks 8-10. If a repeat flow study shows resolution of obstruction or compartmentalization, patients are expected to begin intrathecal mafosfamide during Regimen 1 course 2 of therapy. Patients without a VP or VA shunt who have resolution of normal flow should additionally have an Ommaya reservoir placed.