[Structural analysis of the thickness of human dura mater with scanning electron microscopy]

The only references to the thickness of the human dura mater, reporting its size at various levels, are now 50 years old. Our aim was to study its tridimensional structure with the aid of the scanning electron microscope.

The samples, which were taken 8-12 h after death from 4 human cadavers between 70 and 78 years old, were examined on 2 orthogonal planes (radial longitudinal and transversal).

The architectural structure of the external membrane of the meninges was unusual. The dura mater is made up of elastic collagen fibers organized in successive parallel planes on the surface of the medulla. Each plane constitutes a unit which we will call a sub-laminae. The sub-laminae are found in groups of 8 to 12 that form larger units called laminae, which are between 4 and 5 microns thick. The full thickness of the dura mater at the level of the third lumbar vertebrate contains from 78 to 82 laminae which together measure 270 microns.

The dura mater is made up of a large number of sublaminae that are concentrically parallel to the surface of the medulla. The fibers in general run in all directions and are oriented differently in each sub-lamina. The orientation of fibers that can be seen on the outer or epidural surface corresponds only to the fibers of the outermost lamina, which has a thickness of 78 to 82 microns. A needle that pierces the dura mater passes through some 700 to 800 sublaminae, each with its own particular distribution of fibers.