Brain Tumors

brain tumor

Objectives: You will learn

Characteristics of imaging studies
Common malignant and benign brain tumors
Imaging characteristics of each brain tumor
Systematic evaluation of imaging studies in patients suspected to have brain tumor

Systematic approach to evaluating brain tumors By CT/MR imaging studies

Age:

First decade: Medulloblastoma, Ependymoma, low grade Astrocytoma (Grade I astrocytoma, e.g., Pilocystic astrocytoma, Grade II Astrocytoma), and Craniopharyngioma
Adults:
- Metastasis
- High grade gliomas
  - High grade Astrocytoma
    - Grade 3 Astrocytoma (anaplastic Astrocytoma)
    - Grade 4 Astrocytoma (Glioblastoma)
- Lymphoma
- Benign tumors
  - Meningioma
  - Schwannoma
  - Pituitary macroadenoma

Location (common tumors):

Intra-axial: Metastasis, Astrocytoma
Intraventricular: Ependymoma, Choroid plexus papilloma
Extra-axial:
- Convexity/skull base: Meningioma
- Pituitary fossa: Craniopharyngioma, Pituitary Macroadenoma
- Cerebellopontine angle: Schwannoma

Number:

Single: Primary brain tumor, Solitary metastasis
Multiple: Metastases, Neurofibromatosis.

Tissue Characteristics of Tumors Based Upon T1 and T2 Signal Intensity:

Fat: Lipoma, Dermoid, Teratoma
Calcium: Meningioma, Oligodendroglioma, Craniopharyngioma
Cystic:
- Non-tumoral cyst, e.g., Arachnoid cyst
- Tumors with cysts: Pilocytic astrocytoma (Grade I Astrocytoma), Craniopharyngioma

Signal Intensity:

	T1 wtd. image	T2 wtd. image
Fat:	Bright	Loss of signal on fat suppressed images
Calcification:	Low signal	Darker signal
Cyst/Fluid:	Low signal like CSF	Bright signal like CSF. Fluid follows the signal intensity of CSF within the ventricle and subarachnoid space.

CT imaging is more sensitive than MR imaging to detect calcification within the tumor, tumors originating from the skull and acute hemorrhage within the tumor.

Contrast Enhancement:

Most tumors enhance due to breakdown of blood brain barrier
- No enhancement: Grade II astrocytoma
- Mild enhancement: Grade III astrocytoma
- Inhomogeneous Irregular ring enhancement: Glioblastoma (Grade IV Astrocytoma)
- Smoother ring enhancement: Metastasis
- Homogenous intense enhancement: Meningioma