In Pinched Nerve, we talked about what happens to a nerve that gets squeezed or compressed between 2 hard surfaces. The compression of the nerve causes an interruption of the blood supply that delivers oxygen and nutrients as well as removing metabolic waste products. This situation results with a nerve that is not functioning properly and actually becomes inflamed and irritated. It is easy to visualize this when a disc herniation pushes on a nerve.
What are the symptoms of compression and inflammation?
Three things can happen as a result of the compression and inflammation of the nerve: 1) Pain is produced and this pain can be sharp, aching, or burning. The pain can radiate down the arm or leg in radicular distribution (dermatome) or “strip” of pain. 2) Numbness, decreased sensation, tingling, pins and needles, (paresthesia) might be felt. 3) Muscle weakness can occur in the muscle controlled by a given nerve.
What happens when the blood supply is squeezed out of the nerve?
The picture of the pinched nerve is similar to looking at an “apple core deformity” after someone eats an apple. The core will look quite narrow in comparison to the surrounding fruit that hasn’t been eaten. The narrow part of the core is just like a nerve that is being pinched. In real life, the pinched part of the nerve is blanched because the blood supply has been squeezed out. On either side of the blanched core or compression deformity, there is inflammation of the nerve with redness and swelling.
Can inflammation alone interfere with the blood supply to the nerve?
The answer is yes, inflammation causes swelling. The swelling of the nerve results in increased pressure inside the nerve. Although there are no hard surfaces involved here, the nerve is surrounded and contained by the epineurium. The epineurium acts as a limiting border for the nerve. Any significant swelling of the nerve that results in pressure greater than the blood pressure of the small vessels in the nerve will lead to impaired flow. In this case there is not really a pinched nerve, but a congested nerve with loss of normal blood flow. The symptoms of this inflammation and compression are going to be the same three noted above, but without a disc herniation or stenosis.
What can cause inflammation of a nerve in the spine without a disc herniation?
The answer is that a toxic annular tear can. An annular tear is disruption or fissure of the covering of the disc called the annulus. Many annular tears exist and are found on MRI scans that don’t cause any problem at all. However, there are some tears that are toxic and leak potent inflammatory substances like cytokines and TNA-alpha. If these chemicals come in contact with an overlying nerve, the result is inflammation, with the same symptoms as a herniated disc. It has been reported that up to 20 % of radicular complaints of pain felt in the leg can be due to toxic annular tears. This situation can be very frustrating to patient and doctor alike, when they look for a herniated disc to account for radicular pain in the leg, but the pain is coming from an annular tear.