The effects of puncture of fresh cadaver dura with 20-, 22-, 26-and 29-gauge needfes were observed. A 'tin-lid' phenomenon, manifested with all needle sizes, was capable of sealing the resultant hole. The larger the needle, the larger the hole, while roturion of' the needle bevel 90' to the jibres altered the shape of' the hole. Holes made in thicker parts of the dura tended to retruct more rapidly than those in thinner areas.

SummaryThe effects of puncture of fresh cadaver dura with 20-, 22-, 26-and 29-gauge Spinal anaesthesia has been in use for 100 years but the debate that surrounds the cause of postspinal headache continues. The most plausible explanation is leakage. The spinal needle traverses the dura and produces a hole through which cerebrospinal fluid (CSF) leaks. The loss of spinal fluid in the upright position results in traction on the brain, which induces the typical frontal headache and possibly nausea, vomiting and dizziness. The headache disappears on adoption of the supine position; this phenomenon is reproducible.It was decided to examine the gross structure of thc dura mater in the lumbar region and to observe the effect of durn1 puncture with needles of different sizes. MethodsFresh preparations of dura were obtained from the lumbar region of five cadavers, and the gross anatomy examined. The dura was punctured with Quincke needles of sizes 20, 22, 26 and 29 gauges with the bevels as parallel as possible to the dural fibres and the resultant holes examined. The needle bcvels were then rotated through 90" and re-introduccd through the dura. The effects of penetration of thc durd in areas of different thickness were also observed. Figure 1 is typical of the dura obtained: the fibres were not uniformly parallel and the thickness varied from between 0.5 to almost 2.0 mm. The effect of puncture of the dura with different size needles, the bevels as parallel as possible to the fibres, is shown in the top left of Fig. 2. A 'tin-lid' phenomenon was evident with each needle size: the perforation resembled the top of a tin that had been almost completely opened, but with the lid hinged at one point. The top four punctures in the bottom right of Fig. 2 show the holcs left when the needle bevels had been turned through 90"; they were somewhat rounder and the 'tin-lid' phcnomenon was seen again. ResultsThe hole tended to be ellipsoidal when aneedle was inserted through a thick part of the dura and after a short time tended to shrink (Figs 3a and b). On the other hand, when the same size needle penetrated a thinner part of the dura the resultant hole was larger and shrank much more slowly. Finally, it was observed that even with 20-gauge needles the 'tin-lid' phenomenon could effectively close the hole in the dura. This may explain why in some patients, especially the elderly who have a physiological lower CSF pressure, postspinal headache does not develop despite the use of large gauge needles. DiscussionWe have found that the texture of dura mater and especially the arrangement of the elastic fibres is not uniform as stated in earlier reports.'-' The variation in puncture-hole size depends on the thickness of the dura at the penetration site; the retraction force is greater where the dura is thicker.

HighlightsInguinal/femoral swelling can obtain the appendix.De Garengeot hernia needs to be considered as differential diagnosis in all femoral hernia.A femoral hernia in a woman can obtain the appendix in an open processus vaginalis.Sonography is a valid diagnostic tool for De Garengeot hernia.

HighlightsIntravenous leiomyomatosis within the vena cava can spread rapidly as far proximally as intracardially.Intravenous leiomyomatosis can be removed bluntly through cavotomy.Sternotomy can be avoided, reducing the surgery to a laparotomy.