Memantine for Prevention of Cognitive Late Effects in Pediatric Patients Receiving Cranial Radiation Therapy for Localized Brain Tumors

Inclusion Criteria:

* Age 6 years to 21 years at time of study enrollment
* Diagnosis of localized low grade glioma \[e.g., pilocytic astrocytoma, optic pathway glioma, ogligodendroglioma, ganglioglioma, pleomorphic xanthoastrocytoma (PXA)\], craniopharyngioma, ependymoma, or germ cell tumor
* Initiating focal cranial radiation therapy (photon or proton)
* Laboratory tests \[transaminases (ALT, AST, ALP), BUN and creatinine not greater than twice normal\] and normal ECG
* Speak, read and understand English sufficiently to complete study assessments
* Adequate vision and hearing for valid completion of study measures
* Negative βHCG pregnancy test among females of childbearing age
* Participant must be able to swallow pills (psychology staff will be available to assist with pill swallowing training if needed)
* Parent/Legal guardian available and able to speak, read and understand English

Exclusion Criteria:

* Medical disorder that would endanger subject's well-being (e.g., uncorrected hypothyroidism, cardiac arrhythmia, hypertension requiring treatment, sick sinus syndrome, prolonged QTc)
* History of significant neurological disease including poorly controlled seizures (i.e., \> 1 seizure per month; anti-epileptic medications are acceptable), stroke, or head injury with loss of consciousness
* Psychiatric condition that would preclude or take precedence over study participation (e.g., active psychosis, suicidal ideation)
* IQ below 70 based on baseline/screening assessment
* Treatment with psychotropic medication (psychostimulant, antidepressant, anxiolytic, antipsychotic) within the past two weeks, unless being prescribed specifically as an anti-emetic
* History of substance abuse
* History of hypersensitivity or reaction to NMDA receptor antagonists
* History of prior cranial radiation therapy