Revised: February 2004
1. Diagnostic Pathology
Definitive management of CNS tumours, with few exceptions, requires histologic confirmation. For intra-cranial lesions this is achieved either by biopsy or concomitant with an open procedure for resection. Spinal cord tumours require open procedures for tissue diagnosis. Tumours of the skeletal spine can often be sampled via percutaneous needle techniques under image guidance.
Biopsy techniques include CT or MRI-guided stereotactic procedures. Occasionally a formal craniotomy is required to safely acquire an adequate volume of tissue.
CSF sampling can be useful for analysis of markers of germ cell tumours and carcinomatous meningitis. (CSF sampling must be done with caution in the face of an intracranial mass.)
2. Radiology-Imaging
Brain
a)
Skull radiographs are sometimes useful in demonstrating enlarged pituitary fossa and associated hyperostosis in meningiomas.
b) Computer Tomography (CT) and/or Magnetic Resonance Imaging (MRI) are the primary imaging modalities for patients expected to have brain tumours. Intravenously enhanced CT examinations are usually adequate for supratentorial mid and high grade gliomas and some instances of metastatic disease, lymphoma and meningioma. Low grade glial neoplasms, neuronal and mixed neuronal-glial tumours, ependymal tumours, most embryonal tumours (including medulloblastomas), pituitary/pineal region masses, cranial nerve tumours and some meningiomas should be studied with Gadolinium-DTPA enhanced MRI. MRI has significantly higher sensitivity than CT toward detecting tiny metastases and leptomeningeal carcinomatosis and should be used for these purposes. In general, the trend is toward using MRI for most brain tumours other than those which have known high conspicuity on CT. CT is still the modality of choice for detecting brain tumour calcification and remains useful for defining calvarial and skull base bony involvement.
c) When surgical resection is considered, patients with solitary brain metastasis should be studied by MRI to exclude additional lesions.
Spine
a) The initial investigation should be plain radiographs of the spine. Secondary signs of spinal cord tumour may be shown on the plain films. These include erosion of the pedicles, enlargement of the intravertebral foramina and compression and collapse of vertebral bodies.
b) MRI is definitely the modality of choice in showing intramedullary, intradural, dural and epidural tumours. When MRI is not available the alternative is CT myelography.
c) Routine Staging: MRI of the spine is indicated for medulloblastoma, supratentorial PNETs, pineoblastoma, germ cell tumours due to high risk of spinal cord seeding.
Specific Examples
a) Gliomas
Diagnosis:
- CT and/or MRI with Gd-DTPA
- CT is usually adequate for high grade gliomas
- MRI for low-grade glioma
Post-op: CT without/with contrast 1-4 days post-op
Pre-irradiation:CT or MRI with Gd-DTPA
b) Medulloblastoma
Diagnosis:
Post-op:
- CT brain without/with contrast (between days 1-4)
- MRI of whole spine without and with Gd-DTPA at 2-4 weeks (when MRI not available use CT myelography) for staging
c) Tumours of Meninges
Diagnosis:
- CT or MRI. If CT is used additional coronal images are often useful.
Post-op:
- CT without/with contrast 1-4 days post-op
d) Tumours of the Pituitary Gland
Diagnosis:
Post-op:
- Coronal CT without/with contrast days 1-4
e) Tumours of Specialized Tissues
1) Pineal region
a) High grade lesions, i.e. pineoblastoma, embryonal cell, endodermal sinus, choriocarcinoma, germinoma
Diagnosis:
- MRI brain with Gd-DTPA
- serum and CSF AFP, hCG
Post-op
- MRI brain with Gd-DTPA
- MRI spine with and without Gd-DTPA at 2-4 weeks for staging.
2) Astrocytoma, pineocytoma (astro/neuronal)
Diagnosis:
Post-op:
f) Spinal Cord Tumours
1) Vertebral Body and Epidural Metastases
Diagnosis:
- MRI of suspected region and limited MRI of the rest of the spine.
- CT is useful for defining bony involvement/destruction. If the patient is to be taken to the OR for spinal surgery, CT is generally mandatory for pre-surgical planning.
Post-op:
2) Intradural Extramedullary (including leptomeningeal disease)
Diagnosis:
Post-op:
3) Intramedullary
Diagnosis:
Post-op:
- MRI at 6-8 weeks for those tumours resected, not necessary after biopsy
g) Primary CNS Lymphoma (see Lymphoma, Chronic Leukemia, Myeloma)
h) Solitary Cerebral Metastasis for Surgical Resection
Diagnosis:
Post-op:
- CT without/with contrast days 1-4
