The management of glial tumours varies depending on a number of factors —
• the degree of malignancy
• the presence or absence of raised ICP
• the degree of disability and the effect of steroid therapy
• the suspected nature of the tumour on imaging
• the patient's wishes
Steroid therapy: For patients presenting with symptoms of raised intracranial pressure and/or focal neurological signs, a loading dose of dexamethasone 12 mgs i.v. followed by 4 mgs q.i.d., by injection or orally, reduces surrounding oedema and leads to rapid improvement. Steroid treatment is an essential prerequisite to operation. Its introduction has significantly reduced the perioperative mortality. After several days, a gradual reduction in dosage avoids side effects.
Biopsy: In most patients, imaging is insufficient to diagnose a malignant tumour confidently and biopsy provides a tissue diagnosis. Failure to confirm the nature of the lesion, risks omitting treatment in benign conditions such as abscess, tuberculoma or sarcoidosis. Identification of tumour type and grade gives a prognostic guide and aids
Ultrasound probe further management. METHODS:
Ultrasound guided - a brain cannula inserted into the abnormal region permits aspiration of a small quantity of tissue for immediate (smear and frozen section) and later (paraffin section) - - "Í examination. Provided patients x receive preoperative steroid cover the risks are small, but occasionally biopsy produces or increases a focal deficit or causes a fatal haemorrhage.
Biopsy cannula -on introduction a change in consistency may be detected on encountering tumour tissue
Aspiration of fluid from a cystic cavity may provide a temporary decompression.
Framed or frameless stereotactic methods (see page 372) - permit accurate placement of a fine cannula at a predetermined site selected on CT scan or MRI. Stereotactic guidance is essential for small and/or deep inaccessible lesions (e.g. hypothalamus). Prior selection of the needle path avoids vessels and important structures, thus minimising the risks. Since the degree of malignancy varies from region to region within a single lesion, several samples are taken from different sites to increase accuracy. If findings vary, then the region of greatest malignancy dictates the tumour grade. These techniques are now frequently used, even for more accessible lesions, due to the low mortality and morbidity.
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