NeuroradiologyGlioma
neoplasm derived from glial cells. These tumours are also defined as neuroglial tumours. Corresponding to the three types of glial cells there are three major types of glial tumours: astrocytoma of various degree of malignancy ranging from
benign pilocytic astrocytoma to glioblastoma, oligodendroglioma and ependymoma. Papilloma/
carcinoma of the choroid plexus are considered gliomas since they originate from modified ependymal cells that are contained in the plexus. Primary
cerebral gliomas account for 40 - 45% of all intracranial tumours. Most gliomas occur in the sixth decade of life. There is a topographic difference between the gliomas of adults and those of children. Adult gliomas are mainly supratentorial in location, whereas in children 70-80% are infratentorial. Different incidence of the various histological types for the two age categories is also reported (Table 1).
Glioma, Table 1.
| Adults | Childre (< 15 years) |
|---|
| Malignant astrocytoma 50-60% | Astrocytomas < 50% |
| (Predominantly cerebral) | Cerebellar 30% |
| Benign astrocytoma 25-30% | Brain stem 10% |
| Oligodendroglioma 5% | Oligodendroglioma |
| Ependymoma 5% | Ependymoma 8% |
Gliomas clinically manifest either with focal neurological deficits or seizures, or with signs of increased intracranial pressure such as increasing headache, typically most severe in the morning, nausea, vomiting, visual symptoms and lethargy.
CT scan is the first imaging study to perform in patients with suspected a brain glioma.
MRI (Fig.1) is superior to CT in terms of both tumour detection and delineation, however, both modalities are often inconclusive regarding histological grade of the glioma. Enhancement after contrast injection is better evaluated by MR owing to its superior sensitivity, but it is not specific for different degrees of malignancy of these tumours.
For MR aspects of the different histological types of gliomas, see under specific tumour type.
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a, b. Axial CT without and with intravenous injection of contrast medium. Nonenhancing, hypodense space-occupying lesion infiltrates part of the temporal lobe and insula on the right side. Two arrows indicate the compressed and displaced middle cerebral artery branches within the insular portion of the sylvian cistern.
c. MR, T2-weighted axial image. Marked hyperintensity of the tumour due to the high water content of the neoplastic cells.
d. MR, T1-weighted coronal image. The tumour is markedly hypointense. Arrowheads point on the right side at the elevated sylvian fissure by the enlarged temporal lobe. On the left, arrowheads indicate the normal position of the sylvian fissure. Asterisks indicate infiltration of the tumour towards the insula.
e, f. Right carotid angiogram, AP and lateral projections. Arrows indicate marked elevation of the horizontal portion and most anterior branches of the middle cerebral artery.
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Glioma, Fig.1 (a) | | Glioma, Fig.1 (b) | | Glioma, Fig.1 (c) |
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Glioma, Fig.1 (d) | | Glioma, Fig.1 (e) | | Glioma, Fig.1 (f) |