A Study to See if Memantine Protects the Brain During Radiation Therapy Treatment for a Brain Tumor

Inclusion Criteria: * \>= 4 and \< 18 years at time of study entry * Patients must weigh 15 kg or greater at time of study entry * Primary central nervous system tumors that have not received prior cranial radiotherapy * Planned focal, cranial or craniospinal radiation treatment for a primary central nervous system tumor * The patient must have receptive and expressive language skills in English, French or Spanish since the neurocognitive function and quality of life (QOL) assessment instruments are available in these languages only * Creatinine clearance or radioisotope glomerular filtration rate (GFR) \>= 70 mL/min/1.73 m\^2 or a serum creatinine based on age/sex as follows: * Age: 4 to \< 6 years; Maximum serum creatinine (mg/dL): 0.8 male; 0.8 female * Age: 6 to \< 10 years; Maximum serum creatinine (mg/dL): 1 male; 1 female * Age: 10 to \< 13 years; Maximum serum creatinine (mg/dL): 1.2 male; 1.2 female * Age: 13 to \< 16 years; Maximum serum creatinine (mg/dL): 1.5 male; 1.4 female * Age: \>= 16 years; Maximum serum creatinine (mg/dL): 1.7 male; 1.4 female * Total bilirubin =\< 1.5 x upper limit of normal (ULN) for age * Serum glutamate pyruvate transaminase (SGPT) (alanine aminotransferase \[ALT\]) =\< 135 U/L * Note: For the purpose of this study, the ULN for SGPT (ALT) has been set to the value of 45 U/L * The patient must be able to undergo magnetic resonance imaging * All patients and/or their parents or legal guardians must sign a written informed c…