Artifacts in eighth cranial nerve biopsy.

The occurrence of artifactual morphological changes was investigated in human eighth nerve biopsies and corresponding changes were brought about in biopsies from rats by mechanical handling before fixation. At the very site of compression by a pair of forceps the biopsy stained lighter than in its immediate surroundings. Electron microscopy showed denuded and fragmented axons among vesicular debris in the area. Further away the myelin coats were greatly thickened, often to the degree that the axonal canal could no longer be identified. The myelin lamellae showed separation and were occasionally seen in convoluted forms. Also variations in the diameters of the nerve fibres and ruptures of the meylin coats could be produced after mechanical handling.