[The relief of postspinal headache using the Whitacre cannula. Experimental studies].

The structure of the spinal dura mater and the consequences of puncturing the dural tissue with different types of spinal needles were examined. There is no uniformly longitudinal parallel arrangement of dural fibers in human lumbar dura mater from the segments L3-5, but as shown in both scanning electron microscope imaging and polarized light microscopy the small collagenous fibrils are connected by cross-linked bridges. After perforation with Whitacre's pencil-point needle a kind of double layer membrane surrounds the puncture hole and might be responsible for the rearrangement of dural fibers and sealing of the hole after removal of the needle, like wings closing over each other (curtain-effect). This double layer membrane was not seen after dural puncture with sharp Quincke-bevelled needles.