The American journal of pathology
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A method for the in situ fixation of human meninges for electron microscopic examination is described. It was found that the cranial meninges of humans do not include a subdural space. Instead there is a complex, tight layer of cells, the interface layer, composed in the innermost portion of the dura mater (the dural border cells) and the outermost portion of the arachnoid (the arachnoid barrier layer). ⋯ The fine structural characteristics of these layers are defined. The erroneous macroscopic impression of a subdural space results from an extraordinary lack of cohesion within the dura-arachnoid interface layer conditioned by a) a complete absence of a collagenous reinforcement within this zone, b) the presence of large extracellular cisterns between the dural border cells, and c) a paucity of intercellular contacts within that latter layer. An understanding of the fine structural organization of the interface layer is essential to any consideration of the pathogenesis of subdural lesions: these form within a sheet of torn dural border cells and not within a preexistent tissue compartment.