Hydrodissection for Nerve Entrapment in St. Louis

Peripheral nerves, like the nerves in your arms and legs, run through tunnels and between layers of fascia (sheets of tough tissue). Injury, repeated strain, surgery or inflammation can tie the nerve down to the tissue around it. Then the nerve can no longer glide as the limb moves, and every move tugs on it. The result is burning, tingling, numbness or shooting pain along the path of that nerve.

Using live images, we guide a needle to the space between the nerve and the tissue holding it. Then we push fluid in under pressure to pry the two apart. The nerve is not cut or moved. It is simply set free, so it can glide again.

We use both ultrasound and fluoroscopy (live X-ray) for this. We prefer fluoroscopy where we have it, because contrast dye records where the fluid really spread. Ultrasound shows what X-ray cannot: the nerve itself, the blood vessels around it, and the space opening up live on screen. The two work together. One does not replace the other.

Good candidates usually have nerve pain in one spot, confirmed by exam and electrodiagnostic testing. Common targets are trapped nerves at the wrist, elbow, and around the knee and ankle, including some cases of persistent foot pain. When the nerve has been trapped badly for a long time, hydrodissection may be paired with peripheral nerve stimulation.

You stay awake. It takes about twenty minutes and needs no cut. Some patients feel a change right away as the pressure comes off the nerve. For others, the benefit builds over the next few weeks as the nerve heals. Gentle nerve-gliding exercises afterward help keep the movement the nerve has won back.

A peripheral nerve, like a nerve in your arm or leg, is not fixed in place. As a joint moves, the nerve must slide inside the tissue around it. It must also stretch a little along its length. The median nerve at the wrist and the sciatic nerve at the hip both slide about a centimeter with normal movement. That sliding is built into the design. It is not an accident.

After injury, surgery, repeated strain or inflammation, the loose tissue around a nerve can turn to scar. Then the nerve sticks to the parts around it and can no longer slide. Every move pulls on the nerve instead of letting it glide. Nerves have their own tiny pain nerves, called nervi nervorum. So a nerve that is tied down starts making pain, even when nerve conduction tests stay normal. That is why electrodiagnostic testing can look normal in a patient with clear symptoms.

Hydrodissection uses fluid pressure to split tissue along the natural seam between the nerve and what has stuck to it. Fluid takes the easiest path. So it opens the scar while flowing around the nerve, not through it. On ultrasound, you can watch the split happen as a halo forms around the nerve. That halo tells the doctor the space has opened.

The fluid is chosen on purpose. Normal saline carries electricity, so it can get in the way if nerve stimulation is used to confirm the needle spot. Five percent dextrose in water is often preferred because it does not carry electricity. Some research suggests dextrose also calms touchy nerves beyond the physical split, possibly through TRPV1 channels. That proposed drug effect is less well proven than the physical one. We call it plausible rather than proven.