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Anatomical re‐evaluation of lumbar dura mater with regard to postspinal headache

The effects of puncture of fresh cadaver dura with 20‐, 22‐, 26‐ and 29‐gauge needles 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 rotation of the needle bevel 90° to the fibres altered the shape of the hole. Holes made in thicker parts of the dura tended to retract more rapidly than those in thinner areas.