CNS General Information

Frequency of Primary Intracranial CNS Tumors

Histopathology Primary Brain Tumors (%) Gliomas (%)
Glioblastoma multiforme 21.7 47
Malignant astrocytomas 16.6 36
All oligodendroglioma 3.1 6.7
All ependymomas 2.3 5.1
Low grade astrocytoma 1.8 3.9
Meningioma and other mesenchymal tumors 26.7

Frequency of CNS Tumors

  • Incidence examined by the Neuropathology Department, Institute of Neurological Sciences, Glasgow (2.5 million) over 5 years [1]
Supratentorial Adult Children
High-grade astrocytoma 40% 7%
meningioma 15% --
Metastasis 12% --
Astrocytome 8% 7%
Craniopharyngioma 1% 13%
Neuroma 6% --
Metastasis 4% --
Astrocytoma 1% 27%
medulloblastoma < 1% 24%

Etiologic Factors

  • Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder affecting 1 in 3000 individuals that causes intracranial optic pathway glioma and extracranial benign Schwann cell tumors.
  • Neurofibromatosis type 2 NF2 is far less common than NF1, occurring in only approximately 1 in 35,000 individuals, and is characterized by bilateral acoustic neuromas and meningiomas.
  • Li-Fraumeni syndrome (mutation in p53 allele; malignant gliomas/ GBM);
  • von Hippel-Lindau syndrome (mutation of the VHL gene; cerebral and spinal hemangioblastomas)
  • Turcot's syndrome (germline mutations of the adenomatous polyposis gene; malignant glioma medulloblastoma)
  • The nevoid basal cell carcinoma syndrome (Gorlin's syndrome) is associated with medulloblastomas and subsequent BCC of skin (and possibly an increased risk of meningiomas) and represents mutations in the PTCH gene or other members of the sonic hedgehog signaling pathway.
  • Tuberous sclerosis is a rare, multi-system genetic disease that causes benign tumours to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. TSC is caused by mutations on either of two genes, TSC1 and TSC2, which encode for the proteins hamartin and tuberin respectively. Three types of brain tumors are associated with TSC: cortical tubers, which generally form on the surface of the brain; subependymal nodules, which form in the walls of the ventricles (the fluid-filled cavities of the brain); and giant-cell astrocytomas, a type of tumor that can block the flow of fluids within the brain.

Patholoy and Associated Features

Histopathology Pathologic Features
Glioblastoma multiforme pseudopalisading and microvascular proliferation
Malignant astrocytomas
oligodendroglioma Fried-egg appearance
ependymomas Perivascular pseudo rosettes and ependymal rosettes
Pilocytic astocytoma (Low grade astrocytoma) Biphasic microcyst
Rosenthal fiber formation
Meningioma psammoma body
Schwannomas or neurilemomas Verocay bodies
Germ Cell Tumors
Yolk sac tumor Schiller-Duval bodies (AFP)
Choriocarcinoma Giant cell syncytiotrophoblasts (hCG)
Teratomas no markers produced
Embryonal carcinoma no markers produced
Germinoma (analog to seminoma) may have slightly elevated hCG

WHO Grading System

Regional Brain Syndromes

  • Frontal lobe – cognitive decline
  • Temporal Lobe – agnosias and apraxias and seizures
  • Parietal lobe – sensory or seizures

Lhermitte's sign

  • sometimes called the Barber Chair phenomenon, is an electrical sensation that runs down the back and into the limbs, and is produced by bending the neck forward. This is caused by lesion of the dorsal columns of the cervical cord or of the caudal medulla, classically casued by Multiple Sclerosis
  • is a radiation myelopathy that lastes for 1 to 2 months after sinal cord irradiation. This paresthesia, which occur in 15% to 25% of patients after mantle irradiation for Hodgkin's disease are believed to be secondary to transient demyelination.
  • caused by Behçet's disease, trauma, transient radiation myelopathy, vitamin B12 deficiency (subacute combined degeneration), and compression of the spinal cord in the neck from any cause such as cervical spondylosis, disc herniation, tumor, and Arnold-Chiari malformation.


  • Profoundly demyelinating necrotizing reaction usually noted 4 to 12 monhs afer combine treatment with methotrexate and radiation.

Intrathecal Chemotherapy

  • Methotrexate (MTX)
  • Cytosine arabinoside (ara-c)

Cognitive Testing

  • Memory is measured by the Hopkins Verbal Learning Test (HVLT).

Differential Diagnosis for Adult CNS Tumor++

Sella Tumor

  • pituitary adenoma
  • optic nerve/ cavernous meningioma
  • low-grade glioma

Thalamic Tumors

  • low-grade Glioma
  • high-grade Glioma


  • Brain metastasis
  • GBM
  • low-grade Astrocytoma
  • Ependymoma
  • CNS lymphoma
1. Adams JH, Graham DJ, Doyle D. Brain biopsy. London: Chapman and Hall 1981
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