Surgical "touch artefacts" of the cerebral cortex. An experimental study with light and electron microscopic analysis.

In surgically excised brain tissue a very common artefact, unrelated to the presence or absence of a genuine pathological process, involves the water content of cortical neurons. Nerve cells may show massive watery swelling of both their cytoplasm and nuclei or conversely may become shrunken and dark-staining. The most important aspect of this alteration is that it may lead to mistaken histopathological interpretation, but the question also arises whether such changes, presumably caused by exposure, touch, pressure or the combination of all 3, in the living patient, would persist after surgery and would eventually result in irreversible damage to the involved neurons? Thirty rats were operated in this experiment: craniotomy and opening of the dura mater was done over one convexity and slight pressure (uniformly calibrated for all animals) was applied to the exposed cortex. The wound was closed and the animals were sacrificed at various intervals, ranging from immediately after the operation to 6 weeks. The areas that suffered compression were examined by light and electron microscopy. Initial changes included marked watery swelling of neuronal perikarya and nuclei which predominated over pyknotic changes. The changes thus produced were identical with those seen in portions of the cortex excised immediately after pressure was applied to the area in 10 additional rats.(ABSTRACT TRUNCATED AT 250 WORDS)