What is the difference between epidural anesthesia needle and subarachnoid anesthesia?

These two types of anesthesia are collectively referred to as intraspinal anesthesia, and the intraspinal anatomy is successively ligamentum flavum -- dura dura -- arachnoid -- spinal cord. There is an epidural space between the ligamentum flavum and the dura mater, where an anesthetic is placed, called an epidural. There is an underlying anatomical gap between the dura and the arachnoid membrane, which is generally not clinically distinguishable, and there is a gap between the arachnoid membrane and the spinal cord called the subarachnoid space where an anesthetic is placed called subarachnoid anesthesia. Epidural (lumen) anesthesia differs from subarachnoid anesthesia in that it is bounded by the dura mater.