Pain expert Dr. Scott Fishman answers questions about nerve pain:
Q: What makes diabetes painful and what can be done about it?
A: Diabetes can destroy small blood vessels, which in turn can damage the nervous system, and these damaged nerves can cause pain.
The most common forms of diabetes, juvenile and adult onset, can damage many organs and systems. Diabetes can make it hard to digest food, cause heart disease, and destroy small blood vessels, while the nervous system becomes an innocent, injured bystander. The disease's most common pain syndrome is diabetic neuropathy.
The pain arises from nerves that are injured or malfunctioning. These crippled fibers can be found anywhere along their path, from the tip of the toe to the brain. Diabetes eats away at the thread-thin blood vessels that feed delicate nerve cells.
This is why diabetes pain usually strikes first in the hands and feet. A common pain syndrome from diabetes is described as "stocking and glove" pain because it appears in the hands and feet and usually makes it painful to wear gloves or socks.
Diabetes alters sensation in the smallest nerves, which happen to lie at the end of the peripheral nervous system, in the hands and feet. Diabetes starves these tiny nerves. As a result, the nervous system becomes confused about what is and isn't painful. Stockings, gloves-anything that that touches skin served by these tiny, hypersensitive nerves-is going to send signals to the spinal cord, where they may be mistaken for pain.
It is like having a stereo with frayed wires in the speakers so that you cannot hear music at a normal sound level. To adjust for the poor connection, you crank up the stereo to the highest volume. While the music may get louder, it doesn't necessarily get clearer.
Treatments for this pain are aimed at the nervous system and calming the nerves that are misfiring. The nerves are undergoing tiny seizures and these have to be halted to alleviate the pain. I often start with a five-minute infusion of the local anesthetic lidocaine. If this diminishes the pain, I know that similar drugs that can be taken orally will work for the patient. For instance, I may start with an oral version of an anti-arrhythmic drug, a heart medication that smoothes out irregular nerve activity and acts as an analgesic.
When lidocaine is not effective, I try other types of drugs. Anti-convulsants also quiet erratic nerve signals, and such drugs as carbmazepine (Tegretol), clonazepam (Klonopin), gabapentin (Neurontin), phenytoin (Dilantin), valproic acid (Depakote), and others are as fundamental to pain medicine as sutures are to surgery.
Researchers recently have been looking into other kinds of drugs that halt or slow down the overactive nerves. Animal studies testing a class of drugs called selective calcium channel blockers are raising tantalizing results for easing pain. Scientists are beginning to learn more than ever about newly discovered calcium channels and their tendency to alter the flow of calcium and electric signals in and out of cell membranes.
For years, drugs in this class such as verapamil, nifedipine, diltiazem, nicardipine, and nimodipine have been prescribed for hypertension and arrhythmia. Now, scientists are finding new calcium channel drugs that have special properties, one of which may be potent pain relief.