Confirmation of diagnosis

Two techniques are practiced to confirm a suspected diagnosis of astrocytoma:

• burr hole biopsy - requires pre-operative cover to reduce risk of focal deficit or haemorrhage. A sample of tissue is aspirated through a brain cannula inserted into the abnormal region.
  
  
• stereotactic biopsy guided by CT or MRI - suitable for small and/or deeply inaccessible lesions but small sample size extracted makes histological diagnosis difficult.

The accuracy of any method is reduced by the variation in malignancy in any one lesion. The highest grade obtained in the sample is used to classify the lesion.

Diagnostic biopsy followed by radiotherapy is often the treatment of choice in the elderly and those with marked disability, e.g. severe dysphasia. It is also used to treat hypothalamic astrocytomas which are inaccessible.