This is similar to an epidural in that a needle is put in your back and pain relief is achieved by blocking nerve fibers that supply the pelvic organs. However, in a spinal block, the needle is passed through the epidural space to pierce the membrane covering the spinal cord (the dura) so that anesthetic can be injected into the fluid around the spinal cord; no tubes are left in place. The needle used for a spinal block is smaller than that used for an epidural, which means it's less painful to insert. There is still a risk of a headache as with an epidural (see An epidural "headache") and the side effects should be treated the same way.
A smaller dose of anesthetic is needed and it works very quickly: pain relief is almost immediate, whereas an epidural takes 10-20 minutes. However, the use of a spinal block is limited because only a single dose of medication can be administered. As a result, spinal blocks are usually reserved for use during a cesarean, or for an assisted delivery when an epidural isn't in place.
This involves both a spinal injection and putting an epidural in place. It's sometimes done when problems are encountered with an epidural (see Epidurals) and is also used for a cesarean. A CSE gives pain relief throughout labor. However, it's a specialized technique and isn't offered in all units.