However, the practice of CSE and epidural catheter placement relies on the palpation of anatomical landmarks that are not always easy to feel. Therefore, the epidural needle maybe placed "off midline" despite positive loss of resistance (LOR) that causes negative CSF flow in the spinal needle and an incorrectly placed catheter. As a result, the incorrect catheter placement will result in a "failed" or suboptimal epidural analgesia.