Intracranial Tumors

Overview & Classification - Tumor Terrain Tour

• Intracranial Tumors: Abnormal cell growth in cranium; benign or malignant.
• Origin-Based Classification:
  • Primary: From brain, meninges, nerves, pituitary.
    • Intra-axial: In brain parenchyma (gliomas, medulloblastomas).
    • Extra-axial: Outside parenchyma (meningiomas, schwannomas, pituitary adenomas).
  • Secondary (Metastatic): From distant cancers (lung, breast, melanoma).
• Location: Supratentorial (adults) vs. Infratentorial (children).
• WHO Classification: Histologic grading (I-IV) for prognosis.

⭐ Metastases are the most common intracranial tumors in adults; gliomas are the most common primary brain tumors.

Gliomas - Glial Cell Mayhem

• Most common primary brain tumors; arise from glial cells.
• Classification: cell type & WHO grading (I-IV).

• Astrocytomas:
  • Pilocytic (WHO G I): Children, post. fossa, cystic + mural nodule, Rosenthal fibers.
  • Diffuse (WHO G II): Infiltrative, IDH-mutant common.
  • Anaplastic (WHO G III): ↑cellularity, mitoses.
  • Glioblastoma (GBM, WHO G IV): Commonest adult primary, aggressive, ring-enhancing, crosses midline. 📌 "Butterfly glioma".
• Oligodendroglioma: Calcification, "fried egg" cells. IDH mutation & 1p/19q co-deletion = better prognosis.
• Ependymoma: Ventricular lining/central canal. Perivascular pseudorosettes. Children: 4th ventricle; Adults: spine.

⭐ Glioblastoma (GBM) typically shows central necrosis, significant vasogenic edema, and peripheral enhancement, often crossing the corpus callosum ("butterfly glioma").

Meningiomas - Dural Diva Tumors

• Most common primary intracranial tumor; F:M ≈ 2:1. From arachnoid cap cells.
• Extra-axial, dural-based. Sites: parasagittal, falx, sphenoid wing, convexity.
• CT: Typically hyperdense, homogenous avid enhancement. Calcification (psammoma bodies) common.
• MRI: Isointense on T1, Iso/Hyperintense on T2. Intense homogenous enhancement. Dural tail sign characteristic.
• WHO Grades: I (benign, ~90%), II (atypical), III (anaplastic/malignant).
• Tx: Surgical resection. Radiotherapy for high-grade or incompletely resected tumors.

⭐ Multiple meningiomas, especially spinal, are strongly associated with Neurofibromatosis type 2 (NF2).

Metastases & Other Key Tumors - Beyond the Glia

• Metastases: Most common intracranial tumors in adults. Often multiple.
  • Common Primaries: Lung, Breast, Melanoma, Renal, Colon (📌 LBM-RC).
  • Imaging: Typically at grey-white junction; significant vasogenic edema; ring enhancement common. Solitary mets can mimic primary.
• Pituitary Adenoma: Sellar/suprasellar mass.
  • Microadenoma (<10 mm), Macroadenoma (≥10 mm).
  • "Snowman" or "figure-of-8" sign with suprasellar extension.

  ⭐ Pituitary apoplexy: acute hemorrhage/infarction within adenoma; presents with severe headache, visual disturbances, ophthalmoplegia.

• Schwannoma (Vestibular): Common CPA tumor (CN VIII).
  • "Ice-cream cone" appearance: tumor extending from internal auditory canal (IAC) into CPA. Intense enhancement.
• Meningioma: Dural-based, extra-axial. Homogeneous intense enhancement, dural tail sign.

Pediatric Brain Tumors - Tiny Patients, Big Puzzles

• Pilocytic Astrocytoma: Most common. Posterior fossa. Cystic + mural nodule. GFAP+.
• Medulloblastoma: 2nd common. Vermis/4th ventricle. Malignant. CSF seeding. Homer Wright rosettes.
• Ependymoma: 4th ventricle. Perivascular pseudorosettes. Can occur supratentorially.
• Craniopharyngioma: Suprasellar. Calcification. Rathke's pouch origin. Bimodal age.
• Germ Cell Tumors: Pineal (Parinaud syndrome) or suprasellar (DI, visual field defects).
• 📌 Posterior fossa common: MAE (Medulloblastoma, Astrocytoma, Ependymoma).

⭐ Medulloblastoma often presents with hydrocephalus and signs of ↑ICP due to its common location in the posterior fossa, obstructing CSF flow.

High‑Yield Points - ⚡ Biggest Takeaways

• Glioblastoma (GBM): Most common adult primary brain tumor, often crosses midline.
• Pilocytic Astrocytoma: Most common pediatric primary, typically cystic with mural nodule.
• Metastases: Most common intracranial tumors overall, often at grey-white junction.
• Meningioma: Dural attachment (tail sign), psammoma bodies, generally benign.
• Medulloblastoma: Children, posterior fossa (vermis), Homer Wright rosettes, CSF dissemination risk.
• Craniopharyngioma: Suprasellar, calcification common, "motor oil" cyst fluid.
• Schwannoma: Cerebellopontine angle (CPA), affects CN VIII (acoustic), Antoni A/B histology_