An in vitro study of dural lesions produced by 25-gauge Quincke and Whitacre needles evaluated by scanning electron microscopy

Background and Objectives: A study using scanning electron microscopy showe d that although the laminas forming the dura mater are concentric and paral lel to the surface of the medulla, the fiber layers' orientations are diffe rent in each sub-lamina, dispelling the conventional knowledge that all the fibers of the dura are arranged in a parallel direction. Thus, this study evaluated the dural lesions produced by Whitacre and Quincke spinal needles in the external and internal surface of the dura mater of the lower spine area in an attempt to gain more insight into the pathophysiology of postdur al puncture headaches (PDPH). Methods: The T11-L4 dural membranes from 5 fresh (immediately after extract ion of organs for transplantation), male patients declared brain dead, ages 23, 46, 48, 55, and 60 years, were excised by anterior laminectomy. Morpho logic orientation of the membrane and normal pH were maintained with an app aratus designed for this purpose. One hundred punctures (20 on each sample) at 90-degree angles were done with a new needle each time, 50 with 25-gaug e Whitacre and 50 with 25-gauge Quincke needles. Half of the punctures with the Quincke needles were done with the bevel in parallel direction to the axis of the spinal cord, and the rest with the bevel perpendicular to it. F ixation in solutions of 2.5% glutaraldehyde phosphate buffer, followed by d ehydration with acetone, was done 15 minutes after the punctures. After ace tone was removed at ideal conditions of temperature and pressure, the speci mens were then metallized with carbon followed by gold and inspected under a scanning electron microscope. Results: Twenty-five of the Whitacre and 23 of the Quincke punctures were f ound for evaluation. There were no differences in the cross-sectional area of the punctures produced by the Whitacre or Quincke needles on the dura. T he area of the dural lesions produced by 25-gauge Quincke needles, 15 minut es after they have been withdrawn, was 0.023 mm(2) (confidence interval [CI ] 95%, 0.015 to 0.027) in the external aspect (epidural surface) and 0.034 mm(2) (CI 95%, 0.018 to 0.051) in the internal aspect (arachnoid surface) o f the dural sac. The area of the lesions produced by the 25-gauge Whitacre needles was 0.026 mm(2) (CI 95%, 0.019 to 0.032) and 0.030 mm(2) (CI 95%, 0 .025 to 0.036) in the external and internal surfaces of the dural sac, resp ectively. There were no significant differences in the cross-sectional area s of the punctures produced by the 25-gauge Whitacre or 25-gauge Quincke ne edles. Moreover, with Quincke needles the dural lesions closed in an 88.3% (CI 95%, 86.1 to 92.4) and 82.7% (CI 95%, 74.1 to 90.9) of their original s izes in the epidural and arachnoid surfaces, respectively. With Whitacre ne edles, the closure occurred in an 86.8% (CI 95%, 83.8 to 90.3) and 84.8% (C I 95% 81.7 to 87.3) in the dural and arachnoid surfaces, respectively. Howe ver, there were differences in the morphology of the lesions. The Whitacre needles produced coarse lesions with significant destruction in the dura's fibers while the Quincke needles produced a "U"-shaped lesion (nap) that mi mics the opened lid of a tin can, regardless of the tip's direction. Conclusions: The needles produced lesions in the dura with different morpho logy and characteristics. Lesions with the Quincke needles resulted in a cl ean-cut opening in the dural membrane while the Whitacre needle produced a more traumatic opening with tearing and severe disruption of the collagen f ibers. Thus, we hypothesized that the lower incidence of PDPH seen with the Whitacre needles may be explained, in part, by the inflammatory reaction p roduced by the tearing of the collagen fibers after dural penetration. This inflammatory reaction may result in a significant edema which may act as a plug limiting the leakage of cerebrospinal fluid.