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What is a Pinched Nerve? Part 1
When a patient says they are suffering from a pinched nerve, I can sympathize with their pain and offer my support. But, while the term “pinched nerve” is wonderfully descriptive, it doesn’t help identify the source of the pain or offer a real diagnosis. A pinched nerve can indicate a wide range of spinal problems and it takes a detailed history and a comprehensive examination to discover what the body is telling us.
A pinched nerve might refer to the type of pain you are experiencing. You might feel a particularly sharp, painful sensation in the neck or low back that feels like a pinch. You associate the pain with a nerve because of its sharp, zinging quality. Sometimes when you feel the pinch, it sends a nerve pain down an arm or a leg.
Another way you might use the term pinched nerve is to describe what you think is happening in the body. Perhaps your doctor, a family member or a friend has told you that your neck pain or low back pain, with or without accompanying arm or leg pain, is the result of a pinched nerve.
You may not necessarily feel the pinching sensation, but especially if you have pain shooting down an arm or leg, describing the problem as a pinched nerve seems to make sense.
Let’s look more closely at what causes a pinched nerve.
Pinched Nerve from a Disc Herniation
Usually when doctors talk about a pinched nerve, they are referring to a nerve that is being pinched from a disc herniation with resulting pain in the arm or leg. Rather than thinking that a nerve is being pinched like you would pinch your skin, it is more accurate to think of a nerve being compressed or pushed on.
In this case, a disc has degenerated. It has lost fluid and has lost its normal height. Pressure inside the disc has increased. Cracks or fissures have occurred in the outer rings of the disc allowing the central, gel-like center to push out. This pushing out causes less room for the nerve root as it exits the spinal cord. This condition might exist for years without you feeling any symptoms, or it may never become a problem.
The symptomatic pinched nerve occurs when you push at that nerve just enough to cause injury. Usually a twisting motion of the low back or a simple reaching forward will be the one last insult that compresses the nerve. In the neck there can also be a similar sometimes trivial incident or injury including holding the neck in an awkward position for an extended period of time or repeated minor trauma to the neck from some repetitive activity.
Sometimes a real trauma to the spine from a fall or a severe injury will cause an otherwise fairly healthy disc to herniate, but this is more unusual. Disc injuries can range from minor bulges of the disc to more severe tearing of the disc where the central gel-like material (the nucleous pulposus) breaks out to become a free floating fragment pressing against the nerve.
Once the nerve has been critically pinched, once there is not enough room for the nerve and it has been injured, the body responds with inflammation and you feel pain in the region. This is the body’s intelligent response that helps to protect it from further injury. Protective muscle spasm and limited motion are also part of the body’s response to an injury so close to the critically important spinal cord.
With inflammation at the root of the nerve, the stage is set for what is called radicular pain. Radicular or radiating pain is the pain we feel down the arm when there is injury to a nerve in the neck, or down the leg, like sciatica, with injury to a nerve in the low back. The inflammation we described at the root of the nerve as it leaves the spinal column has traveled along the nerve going down the arm or leg.
If sensory nerves–the nerves that allow us to feel sensation–are injured from the compression caused by the disc, you may feel numbness or tingling in the arm or leg. If the motor fibers of the nerve–the nerves that make muscles work–you might feel weakness in the involved limb.
In Part 2 of our discussion of pinched nerves, we’ll discuss how spinal stenosis can lead to a pinched or compressed nerve, resulting in pain in the back, legs, neck and arms.
(Dr. Arn Strasser is a chiropractor who practices in Portland, Oregon. For more information and appointment questions, please call 503.287.2800.)