[New results in the visualization of the spinal dura mater with scanning electron microscopy]

Although there are various published descriptions of the dura mater spinalis [4, 7, 9, 11, 16], some points relating to the texture of the collagen fibres in the dura have still not been adequately explained. In this study the orientation of the collagen fibril bundles was revealed with the aid of scanning electron microscopy, and our observations have yielded new insights into the three-dimensional structure of the human dura mater spinalis.

The preparations used were taken from the bodies of four persons who had died of acute cardiac infarct at the ages of 70-78 years. The histories of these patients gave no indications of earlier neurological, endocrine or septic illnesses. The tissue examined was taken 8-12 h after death in all cases; it was immediately fixed in glutaraldehyde and then processed for scanning electron microscopy in the usual way.

In the outermost (epidural) layer of the dura mater spinalis the collagen fibres are bunched together in bands that run in all directions. Elastic fibres 2 mm thick are woven into this three-dimensional network of collagen systems. On the inside (the arachnoid side) thin collagen fibres are fused into layers in such a way that the innermost layer resting on the arachnoid has a smooth, shiny appearance comparable to that of a serosa. It is attached to the actual dura with a supporting band of connective tissue. Rests of the subdural neuroepithelium could contribute to the smooth appearance of the superficial aspect.

The outermost layer of the dura is made up mainly of collagen fibres, which run in all three directions--longitudinal, horizontal and transverse--both singly and in groups. These findings are at odds with "classic" descriptions, according to which the fibres in the dura mater spinalis all have a parallel course with a longitudinal orientation in tangential sections.