Regional Anesthesia 22(2):161-166, 1997 New Perspectives in the Microscopic Structure of Human Dura Mater in the Dorsolumbar Region Miguel Angel Reina, M.D.,* Martin Dittmann, M.D.,+ Andr6s L6pez Garcia, M.D.,* and Andr6 van Zundert, Ph.D.* Background attd Objectives. The object of this study was to describe the three-dimen- sional structure of the dura mater by use of scanning electron microscopy. Methods. Microscopic dissection of the dura mater from four fresh cadavers (aged 70, 75, 76, and 80 years) 8-12 hours after death were investigated in three different planes (h)ngitudinal, tangential, and transverse). Resttlts. The external surface of the dura mater, facing the epidural space, consisted of a network of randomly oriented fine collagcn fibers. Thc thicker elastic fibers (2 ~tm in dialneter) were observed on the surface of the dura. In the inner part of the dura mater, there were very fine lamel- lae of collagen fibers, which were bundled into thicker (4-5 [am) layers. The dura mater consisted of 78-82 layers, each layer including 8-12 very fine lamellae. Con- dusions. The fibers of the dura thater do not run in a longitudinal direction and are not arranged in a parallel fashion. Cytoarchitecturally the dura mater is a laminated structure built up from well-defined layers oriented concentrically around the medulla spinalis. Re 9 Anesth 1997: 22: 161-166. Key words: meninges, dttra mater, postdural puncture headache, scanning elec- tron microscopy. The membranes surrounding the brain have been studied by a number of authors (1-6); how- ever, not very much attention has been paid to those membranes that surround the spinal cord. Nicholas and Weller (7) studied the spinal meningcs. Fink and Walker (8) examined the spinal dura mater by transmission electron micro- scopy and reported a typical collagen fiber with a diameter of approximately 0.06 lain. They also From the *Department of Anesthesia, Hospital de M6stoles, Madrid, Spain, the ~Department of Anesthesia and Intensive Care, District ttospital, Bad Sfickingen, Germany, and the tDepartment of Anesthesiology Intensive Care, and Pain Tiler- apy, Catharina llospital, Eindhoven, the Netherlands. Accepted for publication July 24, 1996. Reprint requests: Martin Dittmann, M.D. Chefarzt An~isthesie und Intensivmedizin, Kreiskrankenhaus, D - 79713 Bad S/ickin- gen, Germany. noted that these small fibers were irregular and aligned in various directions. Since Labat (9) in 1930, generations of anesthesiologists have pro- moted his idea to use a puncturing needle oriented parallel to the "longitudinal" dural fibers. It has been said that this direction reduces the incidence of postdural puncture headache (PDPH). On an hi vitro model, Cruickslmnk and Hopkinson (10) mea- sured the loss of cerebrospinal tluid and found that there was no reduction in fluid when the bevel was oriented parallel to the longitudinal axis dur- ing lumbar puncture. Clinical studies that have evaluated PDPH, and particularly those in which needles of the same external diameter have been associated with different rates of PDPtt (11,12), have prompted us to reinvestigate the three- dimensional structure of the human dura mater by means of scanning electron microscopy. 161