Enzymatic destruction of the elastic lamella at the mouth of cerebral berry aneurysm? An ultrastructural study with special regard to the elastic tissue.

Destruction of the elastic tissue is probably an acquired lesion and is decisive for the appearance of cerebral arterial aneurysms at the sites of congenital media defects. The elastic component in the mouths of aneurysms has therefore been studied by electron microscopy, using two new staining methods, i.e. ruthenium-red staining and prolonged osmium-tetroxide treatment. The hypertrophic, duplicated, elastic lamellae showed a disintegration of their luminal portions not earlier described. In close connection with the disintegrated portions, extracellular lysosome-like granules were observed. It is hypothesized that discharged leucocyte grannules containing elastase help to destroy the elastic lamellae.