Background and Objectives. The purpose of this study is to evaluate the effects of puncture of lumbar dura mater with needles of different sizes and with bevels of different shapes.

Methods. After removal, the dura was punctured with different needles (22-, 25-, 27-, and 29-gauge Quincke, 24-gauge Sprotte, 22-gauge Whitacre, and 18-gauge Tuohy needles) and observed by stereomicroscope to examine the gross morphology. Histologic features were observed by light microscope using frozen and fixed samples stained with hematoxylin and eosin or specific methods (Masson and Weigert) to evidence elastic or collagen fibers.

Results. Puncture hole size was proportional to the size of the needle used. Quincke type needles determined oval or ellipsoidal holes; pencil-point needles determined more rounded holes. Dural retraction determined a reduction of the holes in all cases. Histologic examination revealed an irregular border of the hole, with sectioned as well as compressed fibers. The pattern of compressed but not sectioned fibers was observed more frequently in the samples punctured by pencil-point needles.

Conclusions. This study confirms that the arrangement of dural fibers is not as uniform as previously thought. Histologic findings confirm the current opinion that pencil-point needles may be less traumatic than Quincke-type needles. The direction of the bevel of the needle does not appear to have great importance in determining the shape of the hole.