Dr. Robert F. Kidd    

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Caudal Epidural Block

See also: Backache, Sciatica, Prolotherapy

This is a treatment, but also a way of diagnosing, a pinched or irritated nerve root. A "pinched nerve" is a relatively uncommon cause of back or leg pain, but when it occurs, it requires different treatment than for other back problems. Sometimes the diagnosis is not clear, but with an epidural block one can be much more certain of what is causing the problem.

Pinched nerve roots are usually caused by a bulging disc or by a part of a vertebra squeezing the nerve as it leaves the spinal canal. This can cause muscle weakness, but as long as the muscle weakness is not too great and as long as the muscle involved is not an important one (such as in the bladder), the only problem is to relieve the pain. If the pinching is from the disc, one can expect 6 to 12 months of pain without treatment. If it is being squeezed by a vertebra, the duration of pain is harder to predict. It may last days, or years, or come and go in an intermittent manner.

The technique involves injecting a fairly large volume of dilute local anaesthetic into a hole at the base of the spinal canal. This little hole is well below the spinal cord, but the fluid goes up and around it and bathes the nerve roots as they leave the canal. If the fluid reaches the irritated nerve root is will anaesthetize it and the pain will go away immediately. Naturally, as the anaesthetic wears off, the pain returns, but often up to 10 days later the pain mysteriously disappears. It is not clear as to why this happens, but in perhaps 65% of cases this indeed occurs. The pain may return, but repeated injections can often control the pain until it naturally disappears. Cortisone can also be tried if the anaesthetic alone is not effective.

This is not a spinal anaesthetic, as the spinal fluid is not entered. One hour after the injection one can safely get up and go home. It is similar to the epidural injection given in some hospitals for pain relief in child birth, but there is little or no numbness in the lower trunk and legs.

A caudal epidural block is a relatively safe procedure, but rarely, if the sac in which the spinal fluid is contained is lower than usual, the sac could be punctured. One could therefore accidentally perform a spinal anesthetic which would leave one paralyzed for several hours. This should not occur however, as there are ways of determining in fact that the needle is not in the spinal fluid.