Pilocytic (juvenile) astrocytoma of the optic nerve. The influence of biopsy.

The biopsy and the decompression of a pilocytic (juvenile) astrocytoma of the optic nerve may caused increased mucoid formation and increased meningothelial reaction (meningioma formation) and therefore expansion of the tumour remnants. Experiences in the literature and our own clinical, histological and electrron microscopic observations are proof of this thesis. The correct diagnosis is easily established clinically. We should remain conservative if there is no necessity to intervene. A subtotal excision may be harmful.