## Diagnostic Approach to Suspected Glioma **Key Point:** Stereotactic brain biopsy with histopathological examination is the gold standard for definitive diagnosis and grading of CNS gliomas. It is the only investigation that provides tissue confirmation and allows WHO grading. ### Why Biopsy is Essential While MRI provides excellent anatomical and signal characteristics, it cannot: - Definitively distinguish glioma from other lesions (metastases, abscess, demyelinating disease) - Determine WHO grade (I–IV) - Assess mitotic activity, necrosis, or microvascular proliferation - Guide prognosis and treatment planning **High-Yield:** Stereotactic biopsy is minimally invasive, safe, and provides tissue diagnosis in >95% of cases. It is preferred over open biopsy in eloquent brain regions. ### Histopathological Grading Gliomas are graded by WHO criteria based on: 1. Mitotic activity 2. Nuclear atypia 3. Necrosis (high-grade feature) 4. Microvascular proliferation (high-grade feature) **Mnemonic: MANN** — Mitosis, Atypia, Necrosis, Nuclear pleomorphism (features of high-grade glioma). ### Role of Other Investigations | Investigation | Role | Limitation | |---|---|---| | PET-CT (18F-FDG) | Assesses metabolic activity; may help identify high-grade regions | Non-specific; cannot replace biopsy | | DTI | Evaluates white matter tracts for surgical planning | Anatomical only; no tissue diagnosis | | EEG | Detects seizure activity | No diagnostic value for tumor type | **Clinical Pearl:** In inoperable lesions or when diagnosis is uncertain, stereotactic biopsy is safer than attempting resection and still provides tissue for diagnosis and molecular testing (IDH, 1p/19q status). [cite:Robbins 10e Ch 28] 
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