The difference between a spinal tap and an epidural lies in the location where the medication or anesthesia is injected into the body, as an epidural is when the medication or anesthesia is injected into the epidural space, which is right outside of the sac of fluid surrounding the spinal cord; the spinal tap is when the medication or anesthesia is injected directly into the spinal cord fluid, as reported by MedlinePlus. Both injections are typically made at the lower back region, and the region is normally numbed with an topical anesthesia before the injection is administered.
For an epidural, the medication or anesthesia will typically start to have an effect approximately 10 to 20 minutes after it has been administered, and it is typically used for longer surgical procedures. The effects of medication or anesthesia administered through a spinal tap will normally take place immediately. A spinal tap is normally recommended for surgical procedures that can be completed within a shorter period of time.
A catheter is normally placed with an epidural so that patients can receive more medication or anesthesia if needed, while a spinal tap only involves a single injection.
Both a spinal tap and an epidural are known to have fewer side effects than those associated with general anesthesia.