Brain Tumor-Specific Immune Cells (IL13Ralpha2-CAR T Cells) for the Treatment of Leptomeningeal Glioblastoma, Ependymoma, or Medulloblastoma

Inclusion Criteria: * Participant has verified leptomeningeal metastases * Participant must have a Karnofsky performance status (KPS) \>= 60 * Participant must have a life expectancy of \>= 8 weeks * If participant has a ventriculoperitoneal shunt, the valve must be programmable, and must be able to tolerate their shunts being turned off for 48 hours * The effects of IL13Ralpha2-CAR T cells on a developing fetus are unknown. For this reason, women of child-bearing potential must have negative serum pregnancy test and agree to use a reliable form of birth control prior to study entry and for at least two months following study treatment. Male research participants must agree to use a reliable form of birth control and not donate sperm during the study and for at least two months following study treatment * Participant has a histologically confirmed IL13Ralpha2+ tumor expression by immunohistochemistry (IHC) at the initial tumor presentation or recurrent disease (H-score \>= 50) * Participant must have the ability to understand and the willingness to sign a written informed consent * No known contraindications to leukapheresis, steroids, or tocilizumab Exclusion Criteria: * Research participant requires supplemental oxygen to keep saturation greater than 95% and the situation is not expected to resolve within 2 weeks * Research participant requires dialysis * Research participant has uncontrolled seizure activity and/or clinically evident progressive encephalopathy * Failure…