Nerve Blocks in St. Louis

Pain is a signal running along a nerve, like current down a wire. A nerve block puts local anesthetic right around that nerve. It cuts the signal before it reaches the spinal cord and brain. Sometimes we add a steroid to calm inflammation around the nerve and make the effect last longer. The numbing medicine works within minutes, so your response tells us something right away.

A nerve block both tests and treats. That double role is why blocks sit at the center of interventional pain medicine. If numbing one nerve wipes out your pain, that nerve is the path carrying it. No scan can tell you that. That is because a scan shows the parts, not which part hurts. A positive block eases pain and opens the next step, whether that is radiofrequency ablation or neuromodulation of the confirmed target.

We do selective nerve root blocks for radicular pain (pain that shoots down an arm or leg), stellate ganglion blocks for upper-body sympathetic pain, lumbar sympathetic blocks for lower-limb sympathetic pain and complex regional pain syndrome, celiac plexus blocks for upper abdominal pain, sphenopalatine ganglion blocks for cluster headache and facial pain, genicular nerve blocks for knee pain, and cluneal nerve blocks to tell a pinched cluneal nerve apart from sacroiliac and radicular pain.

We do every block with live imaging, using ultrasound or fluoroscopy depending on the target. Most take fifteen to thirty minutes, and you go home the same day. We ask you to track your pain over the next few hours. That is because when the relief comes and how much you get is the test result we are looking for.

Local anesthetics work by plugging sodium channels on the inner face of the nerve membrane. A nerve fires when sodium rushes in. Block the sodium, and the nerve cannot reach its firing point. So the signal cannot pass the treated stretch. The drug has to cross the nerve membrane in its uncharged form, then work in its charged form. That is why numbing medicine works poorly in inflamed, acidic tissue. The acid tips the balance toward the charged form, which cannot get in.

Not all nerve fibers are blocked the same. Small unmyelinated (bare) C fibers and thinly myelinated (coated) A-delta fibers carry pain and temperature. They shut down at lower concentrations than the large A-alpha fibers that carry motor signals to the muscles. That is why a well-placed block can wipe out pain and leave your strength alone. It is also why the order of loss is predictable: temperature, then pain, then touch, then power.

Here is the hard truth from the research on diagnostic blocks. A single positive block is often a false positive. Placebo response is real. The numbing medicine can spread past the target. And a patient hoping for an answer may report relief the drug did not cause.

Doctors handle this with controlled blocks. We repeat the block with a numbing drug that lasts a different length of time. Then we check that the relief matches how long that drug should last. Or we compare against a placebo injection. Say relief lasts about an hour with lidocaine and several hours with bupivacaine. That answer fits how the drugs work. If someone reports the same relief from both, it does not fit. We are strictest about this before any step that cannot be undone, such as radiofrequency ablation. That is where a false positive costs the most.