An important point in CEB is awareness of the distance between the sacral hiatus and dural sac anatomically in relation to the risk of dural puncture. The dimensions of the sacral hiatus may vary, with its apex usually slightly above the distal third of S4, and the distance between the tip of dural sac and hiatal apex around cm. 2 In our study, we used the level of S2 (the dural sac usually terminates at S2 in adults). The distance between the S2 foramen and the apex of the sacral hiatus was () mm on average (range 11–62 mm) and the distance to the base of the sacral hiatus was () mm (range 39–85 mm). We believe, in the light of these data, that the needle should be advanced only a few millimetres after penetrating the sacrococcygeal membrane in adults, in order to reduce the frequency of dural puncture and other possible complications. However, total spina bifida and detection of the dura mater just beneath the hiatus have been reported in 1% of cases. 2 A total posterior closure defect was observed in two of our sacral bones (total spina bifida %).
Cauda equina is formed by nerve roots caudal to the level of spinal cord termination. Cauda equina syndrome has been defined as low back pain, unilateral or usually bilateral symptoms in the distribution of sciatic nerve, saddle sensory disturbances, bladder and bowel dysfunction, and variable lower extremity motor and sensory loss. This may occur with neurotoxicity from local anesthesia. In the past, continuous spinal catheters with local anesthetics were associated with this syndrome. Those types of catheters and infusions are no longer in use.