The word “pinch” means getting caught between two hard surfaces. When we talk about a pinched nerve in the spine, we could be referring to a single nerve, a group of nerves (cauda equine) or the spinal cord itself. Pinching refers to the pressure applied to the nerve.
When the nerve is pinched it will stop functioning properly, in large part, because the blood circulation will be impeded. The blood supply delivers nutrients and oxygen; it removes metabolic waste products.
Any part of the spine can cause the pinching. This means that there can be soft tissue and bony causes that act as the hard surfaces pushing on the nerve(s). The soft tissue and bony causes can act alone or in concert with each other to cause the pinching.
How do we become aware of a pinched nerve?
We become aware of a pinched nerve when the nerve stops working properly. It stops working properly because of the pressure that interrupts the blood supply. Three things can happen as a result of excess pressure on the nerve:
- Pain is produced and this pain can be sharp, aching, or burning. The pain can radiate down the arm or leg in distribution of a “strip” or dermatome.
- Numbness, decreased sensation, tingling, pins and needles, (paresthesia) might be felt.
- Muscle weakness can occur in the muscle controlled by a given nerve.
The most common experience we have all had is feeling an arm “fall asleep” when laying on it the wrong way. The numbness or tingling resolves quickly when we change positions and get the pressure off the nerve.
What causes a pinched nerve in the spine?
There are many things in the spine that can pinch a nerve. There are three main soft tissue examples.
A herniated disc is a common cause of nerve compression and can occur in the cervical or lumbar spine. The herniation can occur in the central or foraminal canal of the spine and the location and level of the herniation will determine which nerves get pinched.
Thickened ligamentum flavum is a common cause of nerve compression. The ligamentum flavum is a layer of soft tissue that lines the spinal canal. The ligamentum flavum can get thicker with age. The flavum can also buckle and fold over on itself as the discs degenerate and lose height as we age. The flavum is thick anyway and when it folds over on itself it can really occupy some space in the spinal canal and compete for space with spinal cord or cauda equina in the spine.
A synovial cyst can be quite large and compete for space too. The synovial cyst is an out-pouching of the synovial lining of the facet joint. The facet joints are located throughout the entire spine, but synovial cysts occur most commonly in the lumbar spine. The cysts are filled with synovial fluid produced be a degenerative facet joint. As the degenerative facet joint produces extra fluid, it forces the synovial lining to produce a “balloon” filled with synovial fluid. This “balloon” of fluid pushes its way into the spinal canal and competes for space with the nerves.
Bony examples would include spurs and overgrowth (expansion) of bone from degenerative changes.
Spurs are easy to visualize and usually are the result of some degenerative process. As they get more prominent, they can compete for space or just impale a nerve.
Bony overgrowth is easy to understand by looking at the finger joints of an older person. The knuckles are often large enough to require a ring to be resized. This is bony overgrowth from degenerative changes. This overgrowth may not cause much problem in the hand, but when this occurs in the spine, pinched nerves can result as the bone grows into a spinal canal and competes for space with a nerve or nerves.
What does the location of pain or numbness tell us?
Each nerve passing through the spine is going to supply a certain part of a foot, leg, thigh or buttock with sensory fibers. Each nerve will supply sensation to a “strip” (dermatome) of the skin. There is a fair amount of consistency between individuals about the nerve that gives sensation to a given strip or dermatome. For example, pain or numbness on the side of the thigh and/or leg usually means that the L5 nerve root is getting pinched. Pain or numbness on the heel often means that the S1 nerve root is being pinched.
In the event that both arms or both legs are affected, the problem might be located in the central spinal canal where the spinal cord is located. In this case, the spinal cord or cauda equina is pinched before the nerves branch off to right and left extremities.
How do you figure out which nerve is pinched?
The first thing I like to do, to figure out which nerve is the pinched nerve, is to ask where one feels the pain or numbness. The nerve supply to each area of the body is quite consistent although there is some variation in a certain percent of the people. For example, any pain or numbness felt on the outside of the thigh is almost always indicates a problem with the L5 nerve root.
If the pain or numbness is bad enough, an MRI scan will often be ordered. The MRI scan can show both soft and bony tissue problems that can pinch a nerve. This test uses a powerful magnetic field to produce detailed views of your body in multiple planes. Disc herniations, stenosis, and synovial cysts are easily seen on an MRI scan.
An EMG is a electromyograph, it is performed by inserting a needle electrode through your skin into various muscles. The test evaluates the electrical activity of your muscles when they contract and when they’re at rest. The test can sometimes tell if there is damage to the nerves leading to the muscle. This is not the most reliable test and I don’t use it that often.
NCV (nerve conduction velocity) is a nerve conduction study. This test measures how fast electrical nerve impulses travel and whether there is any slowing in certain places. The NCV measures the speed of electrical impulses when a small current passes through the nerve. The idea is that it takes longer for an impulse to pass through a pinched part of the nerve than the normal part. This test can be especially helpful to see if a nerve is pinched in two places (double crush syndrome).
Treatment of a pinched nerve
The response of a nerve getting pinched is usually to swell. Swelling is a result of inflammation and the nerve increases in size. The increase in size also increases the likelihood of more pinching.
Rest and diminished activity are the first things to do, but may not be enough. Anti-inflammatory medications can help to reduce the swelling of a nerve. Anti-inflammatory medications might be helpful and can be purchased over the counter. Examples are aspirin, Motrin or Aleve. More powerful anti-inflammatories, like steroids (Medrol dose pack), have to be prescribed by your doctor.
The next level of treatment might be a cortisone injection into the area of inflammation. Examples of steroid injections include epidural steroids or transforaminal steroid injections. Cortisone is a steroid and powerful anti-inflammatory that can shrink swollen tissues and help reestablish the blood circulation.
If time, rest, anti-inflammatories or injections don’t relieve the pain, weakness and numbness, then a decompressive type of surgery might be necessary. The goal of decompressive surgery is to remove the hard surfaces that are pinching the nerve. Examples of hard surfaces to remove include the herniated disc (discectomy), or area of bony stenosis (laminotomy). The more limited the surgery to accomplish the decompression, the better it is for you. There are very few examples where “less is better”, but spine surgery is one of them. Less surgery means less pain, less narcotics, less scar tissue formation and less recovery time. I think that endoscopic spine surgery is the ultimate in minimally invasive surgery without a fusion.
Pinched nerve due to herniated disc
If a nerve is pinched for only a short time, there’s usually no permanent damage. Once the pressure is relieved, nerve function returns to normal. However, if the pressure continues, chronic pain and permanent nerve damage can occur.
Your doctor will ask about your symptoms and conduct a physical examination.
If your doctor suspects a pinched nerve, you may undergo some tests. These tests may include:
- Nerve conduction study. This test measures electrical nerve impulses and functioning in your muscles and nerves through electrodes placed on your skin. The study measures the electrical impulses in your nerve signals when a small current passes through the nerve. Test results tell your doctor whether you have a damaged nerve.
- Electromyography (EMG). During an EMG, your doctor inserts a needle electrode through your skin into various muscles. The test evaluates the electrical activity of your muscles when they contract and when they’re at rest. Test results tell your doctor if there is damage to the nerves leading to the muscle.
- Magnetic resonance imaging (MRI). This test uses a powerful magnetic field and radio waves to produce detailed views of your body in multiple planes. This test may be used if your doctor suspects you have nerve root compression.
- High-resolution ultrasound. Ultrasound uses high-frequency sound waves to produce images of structures within your body. It’s helpful for diagnosing nerve compression syndromes, such as carpal tunnel syndrome.
The most frequently recommended treatment for pinched nerve is rest for the affected area. Your doctor will ask you to stop any activities that cause or aggravate the compression.
Depending on the location of the pinched nerve, you may need a splint or brace to immobilize the area. If you have carpal tunnel syndrome, your doctor may recommend wearing a splint during the day as well as at night because wrists flex and extend frequently during sleep.
A physical therapist can teach you exercises that strengthen and stretch the muscles in the affected area to relieve pressure on the nerve. He or she may also recommend modifications to activities that aggravate the nerve.
Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin IB, others) or naproxen sodium (Aleve), can help relieve pain.
Corticosteroid injections, given by mouth or by injection, may help minimize pain and inflammation.
If the pinched nerve doesn’t improve after several weeks to a few months with conservative treatments, your doctor may recommend surgery to take pressure off the nerve. The type of surgery varies depending on the location of the pinched nerve.
Surgery may entail removing bone spurs or a part of a herniated disk in the spine, for example, or severing the carpal ligament to allow more room for the nerve to pass through the wrist.