On MR spectroscopy of a cerebral abscess, which metabolite peak is classically absent that is present in glioma?
- A Creatine peak
- B NAA (N-acetylaspartate) peak
- C Amino acid peaks (leucine, isoleucine, valine at 0.9 ppm)
- D Choline peak ✓
Explanation
In cerebral abscess, MR spectroscopy of the abscess cavity shows amino acid peaks (at 0.9 ppm — branched chain amino acids from proteolysis), acetate (1.9 ppm), succinate (2.4 ppm), and lactate, but notably absent are choline and NAA peaks (which are neuronal/cell membrane markers absent in pus). Gliomas show elevated choline and decreased NAA. The amino acid peaks are virtually pathognomonic of pyogenic abscess and distinguish it from necrotic tumor. Creatine is a baseline reference metabolite used in ratios, reduced in both tumors and abscesses relative to normal brain.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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