How Do You Irritate a Nerve?

As a physical therapist, I often evaluate and treat patients with a “pinched nerve.” These people usually have low back pain and are starting to feel pain in the buttock, thigh, or lower leg, which is the typical onset of sciatica. Often times, the patient has been to their family doctor and has been prescribed anti-inflammatory or analgesic medication to treat the “pinched nerve.” When these medications fail to work to decrease or abolish the patient’s pain, he or she usually expresses frustration. The pain persists, and the nerve is still irritated.

So how do you irritate a nerve? Why do nerves get pinched? Why does medication seem so ineffective at abolishing pain?

To start to relieve irritation around a nerve, the patient must first understand the various ways in which a nerve can get irritated. Scientific literature has demonstrated three ways to irritate a nerve: fire, chemical irritation, and mechanical irritation.

Fire: The first way to irritate a nerve, and thus have the nerve produce an action potential to tell the brain that a problem is occurring, is to set it on fire. Luckily, in my 17+ years as a physical therapist, I have never evaluated or treated a patient who was on fire. Thus, fire and heat damage to the nerve is easily ruled out.

Chemical Irritation: When a structure in the body pinches a nerve, a host of chemical reactions occur to begin the healing process. There is increased blood flow (and thus, swelling) to the area to begin to remove damaged tissue and prepare the tissue for healing. This blood is caustic to the nerve, and causes chemical irritation, which is registered as pain. This process is important, because the pain tells the patient that something has gone wrong and that a nerve is being pinched and requires attention. The increased blood flow and swelling that occurs with inflammation usually lasts about seven days. The analogy I tell my patients is to go home and hit your thumb with a hammer. You can then see the redness and swelling that occurs with chemical irritation. Of course, there is also pain with this procedure, and most patients do not smash their own thumbs with hammers to prove this point. Anti-inflammatory medication is usually helpful during this early stage of healing but usually offers little relief after the seven day mark.

Mechanical Irritation: Mechanical irritation to a nerve occurs with the nerve tissue is mechanically displaced by forces such as compression or tension. Most “pinched nerves” in the body are the result of mechanical irritation. For example, simply bend your finger backwards slowly until stretch is felt. There is mechanical displacement of the tissues around the finger joint, and a stretch is felt. If you continue to bend your finger backwards, damage to the structures will occur, and pain will be felt. After the initial week of chemical irritation that occurs in the initial inflammatory stage of tissue healing, pain should subside, unless the tissues around the joint continue to be mechanically displaced. Therefore, mechanical displacement of tissues beyond their tolerance causes pain. Since there is little or no chemical component to this pain, medication becomes rather ineffective, and a mechanical solution to the pinched nerve must be found.

That's where we come in.

As a PT, our job is to determine the mechanical cause of your pinched or irritated nerve and find a mechanical solution to the problem. This usually involves exercise (in the correct direction), manual therapy, or a combination of the two.

If you have a pinched nerve, give us a call or email us and come see us. We can perform a mechanical assessment of your condition and help find the right way to relieve the irritation around your nerve.