A lumbar sympathetic block is used as both a diagnostic test and a treatment for overactive sympathetic nerves in the lower back. It has the potential to relieve the pain of reflex sympathetic dystrophy, shingles, and phantom limb pain, and to alleviate the symptoms of some types of peripheral vascular disease.
The Sympathetic Nerves
Your sympathetic nerves are part of your peripheral nervous system. They control bodily processes that you do not have voluntary control over, such as your heart rate, digestive activity, blood pressure, and sweating. The nerves run in a cable-like bundle along your spine; the lumber sympathetic nerves are found in your lower back.
It is normal for your sympathetic lumbar nerves to transmit pain sensations from your legs and lower body to your brain when you are injured. A problem arises when the initial injury is healing well, but the nerves continue to send unnecessary pain alerts. This overactivity of the nerves can occur even after a relatively minor bump or fall, and it is called reflex sympathetic disorder (RSD).
Besides pain, RSD can also cause the blood vessels in your legs to constrict. This decreases the blood flow, leading to pain and a sensation of coldness. The skin over the affected area may appear shiny or scaly with a red or blue cast. Your leg may also swell and feel stiff, affecting your mobility.
Lumbar Sympathetic Block
The purpose of the lumbar sympathetic block procedure is to diagnose RSD and, if appropriate, temporarily block the activity of the lumbar sympathetic nerves. The procedure is done under light sedation and takes about 30 minutes. Most people tolerate the block well, but you will not be a candidate if you are allergic to the anesthetic or dye that is used or if you have other medical complications that could put you at increased risk.
The lumbar sympathetic block is performed while you are lying on your stomach. A fluoroscopy, which is a kind of real-time X-ray, will be ongoing during the procedure. You will receive light sedation, and the skin over the treatment area will be cleaned and a local anesthetic applied.
Your doctor will insert a needle into the area to be treated and inject a dye that can be seen on the X-ray. This is a test to determine how the block itself will spread, and it ensures that you will not be over-treated by having too large an area blocked. Next, the doctor will inject the actual anesthetic around the sympathetic nerve that is suspected of causing the problem. This injection is done slowly over the course of a few minutes to maintain the delicate control that is needed.
When the injection is concluded, a small bandage is placed over the injection site and you will be moved to a recovery area for about 30 minutes. If the lumbar sympathetic block was done for diagnostic purposes, an almost immediate cessation of pain and a feeling of warmth in the affected leg is a confirmation of the diagnosis. This tells the doctor that it was overactive sympathetic nerves causing your pain and that the treated area was the correct location. You will experience the same pain relief and warmth following each subsequent treatment. You can also expect the texture and color of your skin to return to normal, your leg swelling to subside, and your mobility to improve.
Complications from lumbar sympathetic blocks are uncommon, and most people only experience some soreness at the injection site. You may also have slight numbness in the leg if the block bled over slightly from the intended treatment area, and this numbness may last for a few hours. You can expect to go back to work and resume normal activities the day after your procedure.
Duration of Treatment
Different patients respond to the lumbar sympathetic block in different ways. The ultimate goal of the block is to disrupt the activity of the disordered nerves so they will resume their normal functioning after the anesthetic wears off. One treatment is rarely enough, so it is usually repeated at intervals of one to two weeks. Some patients experience lasting relief after two to four treatments, while others may need more than 10 injections. The procedure is most successful if it is used early in the course of the RSD or other disease, such as shingles or phantom limb pain.