Approach to brain tumors

Gliomas - most common

• Astrocytoma - most common glioma
  • Pilocytic astrocytoma - low grade
  • Anaplastic - intermediate grade
  • Glioblastoma multiforme (GBM) - 50% of astrocytomas, high grade, older age group, can cross midline (butterfly lesion across corpus callosum)
• Oligodendroglioma
• Ependymal tumors
  • Ependymoma - likes to squeeze through foramen (Lushka or aquaduct), "plastic" tumor, younger patients
  • Subependymomas - older patients
• Chorid plexus papilloma and carcinoma - intense enhancement, drop metastasis, hydrocephalus

Meningeal and mesenchymal tumors

• Meningioma - 90% are typical (benign), hyperdense on CT with avid enhacement, round, sharpley marginated, extra-axial, dural tail, mother in law lesion on angio "comes early and stays late"
• Hemangiopericytoma
• Hemangioblastoma - uncommon, a/w VHL, cystic mass with mural nodule

Neuronal and mixed glial/neuronal tumors

• Gangliogliomas and Ganglioneuroma - cystic, slow growing benign tumors, children and young adults, temporal and frontal lobes, often present with long standing seizures, frequently have calcifications
• DNET (Dysembryoplastic Neuroepithial Tumor) - cortical based, temporal, present with long stading seizures, bubbly appearance
• Central neurocytoma - heterogeneous mass arising from septum pellucidum

Germ cell tumors

• Germinoma - pineal most common, radiation therapy sensitive, 10-30 year olds
• Teratoma - exclusively in male children

Primitive Neuroectodermal Tumors (PNET)

• Medulloblastoma - roof of 4th ventricle, agressive, densly packed cells (restricted diffusion)
• Retinoblastoma
• Primary cerebral neuroblastoma (supratentorial)
• Pineoblastoma - highly malignant pineal tumor, peripheral calcifications
• Ependymoblastoma

Pituitary tumors

Nerve sheath tumors

• Schwannoma - Benign tumors of crainial or peripheral nerves, multiple a/w NF2
• Neurofibroma - plexiform neurofibromas of peripheral nerves a/w NF1

Hematopoetic Tumors

• Lymphoma - hyperdense on CT, can involve corpus calosum and cross midline, responds to seroids and radiation therapy, primary CNS lymphoma a/w AIDS (may be difficult to differentiate from toxoplasmosis)
• Leukemia

Tumor like

• Hypothalamic hamartoma - gelatic seizure, floor of 3rd ventricle, iso to GM, no enhancement
• Lipoma
• Epidermoid/Dermoid - congenital tumor arising from ectodermal elements in neural tube at closure
  • Epidermoid - squamous epithelium, adults, CSF density on MRI, non-enhacing, restricted diffusion, rare to rupture, CPA most common
  • Dermoid - contain har, sebaceous fat, glands, common in spine, rupture common, younger adults, no enhancement, proteinaceous fluid on MRI

Metastasis

• Found at the junction of gray and white matter
• Most are T2 bright and enhance
• Solitary brain mass has a 50% chance of being metastasis

Mimics

• Include: abscess, hematoma, infarct, multiple sclerosis (tumifactive MS has less mass effect than expeted for size, incomplete rim of enhancement), aneurysm, radiation necrosis, herpes encephalitis (restricted diffusion), arachnoid cyst, colloid cyst, etc

Pearls

• Vasogenic edema from tumor, trauma or hemorrhage spares cortex, responds to steroids
• Cytotoxic edema from ischemia or infection affects both gray and white matter

Differentials

Pediatric Infratentorial

• Pilocytic astrocytoma
• Medulloblastoma
• Ependymoma
• Brainstem astrocytoma

Pediatric Supratentorial

• Astrocytoma
• Pleomorphic xanthoastrocytoma
• PNET (Primitive NeuroEctodermal Tumor)
• DNET (Dysembryoplastic Neuroepithial Tumor)
• Ganglioglioma

Adult Infratentorial

• Metastasis
• Hemangioblastoma - uncommon

Adult Supratentorial

• Metastasis (50% are solitary)
• Gliomas
  • Fibrillary astrocytoma
  • Anaplastic astrocytoma
  • GBM
  • Oligodendroglioma

Cerebellar Pontine Angle (CPA) Mass

• Schwannoma (90%) - only one which expands the IAC (others can invade)
• Aneurysm, arachnoid cyst
• Meningioma, metastasis
• Epidermoid, ependymoma

Pineal tumors

• Germ cell (>50%) - germinoma, teratoma, etc
• Pineal cell (25%) - pineoblastoma (malignant), pineocytoma (benign)
• Glioma

Rim Enhancing Lesions

• Metastasis
• Abscess
• Glioma, granuloma
• Infarct
• Contusion

• Demyelination
• Resolving hematoma

Common Tumors with Calcifications

• Oligodendroglioma
• Ependymoma
• Craniopharyngioma
• Choroid plexus tumor
• Meningioma