Neuroradiology

Oligodendroglioma

is a slow growing glial tumour, usually of the adult, that originates from the oligodendrocyte, the cell that produces and maintains myelin. It is slightly less common than astrocytoma, and is located mainly in the white matter with a superficial growth toward the cortex in the frontal and frontotemporal regions.

Pathologically, oligodendrogliomas are solid, infiltrative lesions with poorly defined borders. In about one-half of the cases they contain cellular elements of other glial types, and are considered "mixed". Coarse intratumoral calcifications are quite common, as is focal cystic necrosis. The incidence of oligodendrogliomas is 5-7% of all primary intracranial tumours and 5-10% of all gliomas.

The peak incidence is in the fourth to fifth decades; they are rare in children. Clinical presentation is usually seizures and headache.

The CT appearance (Fig.1) is characterized by the hyperdensity of the coarse calcifications when present; otherwise the tumour is hypodense with patchy areas of enhancement of the solid portions of the tumour. MR is nonspecific with mixed T1 iso-hypointensity, T2 iso- hyperintensity and enhancement of the solid portions of the tumor. Calcifications are poorly shown by MR. Anaplastic oligodendroglioma has no specific imaging features.

 

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Fig.1

a, b. Axial CT without contrast. Extensive hypodensity of the right temporal lobe, involving the insula, with mass effect, compression of the right lateral ventricle and contralateral displacement of the third ventricle and pineal gland. Coarse calcifications in the deepest part of the tumour c, d. T2-weighted axial MR images. Marked diffuse abnormal signal in the temporal lobe, insula and frontal lobe. The calcifications are barely seen. It is almost impossible to distinguish tumour from oedema although parts of the tumour are hypointense. e, f. T1-weighted coronal MR images; the tumour is inhomogeneously iso- or hypointense. The mass effect with compression of the brainstem and transtentorial herniation (e) is well appreciated. g, h, i. T1-weighted axial, coronal and sagittal MR images following gadolinium injection. Inhomogeneous enhancement of the solid components of the tumour is see. Marked compression and displacement of the brainstem due to transtentorial herniation of the hippocampus.
Oligodendroglioma, Fig.1 (a)
Oligodendroglioma, Fig.1 (b)
Oligodendroglioma, Fig.1 (c)
Oligodendroglioma, Fig.1 (d)
Oligodendroglioma, Fig.1 (e)
Oligodendroglioma, Fig.1 (f)
Oligodendroglioma, Fig.1 (g)
Oligodendroglioma, Fig.1 (h)
Oligodendroglioma, Fig.1 (i)