DISEASE CHARACTERISTICS: Part I: Presurgical: presumptive diagnosis of intracranial glioma and scheduled to undergo first surgical resection OR stereotactic biopsy Postsurgical: Histologically proven intracranial glioma and scheduled to undergo surgical debulking Evaluable preoperative proton magnetic resonance spectroscopic imaging (1H-MRSI) and diffusion magnetic resonance imaging (DI) scans completed within 1 week prior to surgery Postoperative MRI, 1H-MRSI, and DI scans completed within 3 days after surgery Part II: Presurgical: presumptive diagnosis of intracranial glioma Postsurgical: Histologically proven intracranial glioma No surgery prior to completion of exit scans Clinical indication for increasing steroid dose Planned steroid changes must be from 0 to 16 mg/day or a twofold increase Evaluable 1H-MRSI and DI scans No prior treatment on this protocol Parts I and II: No contraindications for magnetic resonance imaging (MRI) (metallic implants, shrapnel fragments, claustrophobia, allergy to MRI contrast)