Low grade astrocytoma: A poorly defined region of low density on CT scan without contrast enhancement suggests a low grade tumour (grade I or II) with a better prognosis. In such patients who often present with epilepsy without other symptoms, there is no evidence that active intervention with operation and/or radiotherapy changes outcome. In this instance, both clinician and patient may prefer to follow a conservative approach. If subsequent CT scanning shows definitive tumour progression (expansion or contrast enhancement, or if clinical symptoms supervene, then surgical treatment and radiotherapy can follow as appropriate.
About 50-60% survive 5 years irrespective of treatment; about 40% survive 10 years. OLIGODENDROGLIOMA
Oligodendrogliomas are far less common than astrocytomas. They occur in a slightly younger age group - 30-50 years, and usually involve the frontal lobes. Occasionally involvement of the ventricular wall results in CSF seeding. Calcification occurs in 40%.
In contrast to astrocytomas, the tumour margin often appears well defined. Oligodendrogliomas are usually low grade tumours, but the rate of growth and the degree of malignant change can vary and anaplastic forms can exist. Malignant change may result in a histological pattern resembling glioblastoma multiforme.
Tumour edge well demarcated -,
Tumour edge well demarcated -,
present in 40%
Some tumours involve the ventricular wall - CSF seeding may occur Management: as for astrocytomas. Low grade lesions may benefit from 'complete' or 'partial' excision. Radiotherapy has most effect in malignant tumours. Prognosis: depends on the tumour grade. Long term survival (over 20 years) is occasionally recorded, but in tumours showing malignant change, expected survival compares closely with that of malignant astrocytoma.
Mixed astrocytoma/oligodendroglioma: Histology may reveal a mixed form with areas of astrocytic change scattered between the oligodendroglioma. In these, grading and outcome depends on the astrocytic component.
Hypothalamic tumours usually occur in children; they are usually astrocytomas of the pilocytic (juvenile) type. The clinical effect of hypothalamic damage takes different forms. Initially the child fails to thrive and becomes emaciated. Signs of panhypopituitarism may develop. Eventually an anabolic phase results in obesity accompanied by diabetes insipidus and delayed puberty. Disturbance of affect and of sleep - wake rhythms may occur.
Upward rumour extension may obstruct the foramen of Munro and cause hydrocephalt
Involvement of the tuberal region may result in the rare presentation of precocious puberty with secondary sexual characteristics developing in children perhaps only a few years old.
Downward extension invades the optic chiasma and impairs vision. Management: The site of the lesion prevents operative removal; a stereotactic biopsy may aid tumour identification. If hydrocephalus is present, a bilateral ventriculoperitoneal shunt relieves pressure symptoms. Radiotherapy is of doubtful value.
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