In our last blog post, we discussed the fact that neuropathy is a generic term that refers to a dysfunction, pathology, irritation, disease or damage to a nerve. It is commonly used inaccurately to describe a specific nerve condition, when in reality there are dozens and dozens of different type of neuropathies.
We also discussed the concept that nerves are divided into “central” or “peripheral” nerves, based upon their location relative to the spine. Those nerves found within the spinal cord and brain are considered part of the central nervous system; whereas, those found outside the spinal cord are considered peripheral nerves.
Peripheral nerves include the part of the long spinal nerve “roots” that exit from the spine all the way down to the final termination of that nerve—even when it is at the tip of the big toe! Each nerve root contains hundreds of individual nerve fibers that control everything from pain sensation, muscle function, position sense, vibratory sense, hot/cold sensation, light tough, deep touch, discriminatory touch, etc.
In our office we utilize several cutting-edge treatment technologies, to include MLS deep tissue laser therapy, and spinal decompression to treat various types of peripheral neuropathies. But before we can determine how our therapy can be properly applied, we must understand the causative factors for each neuropathy. And in many cases, there are more than one factor causing the peripheral neuropathy.
As the nerve roots exit the spinal cord they become more prone to injury than when they were inside the cord. This is due to several factors. The first is the fact that the spinal cord is well protected by the bony vertebral column and the protective cerebral spinal fluid that acts as a cushion to the cord and nerves. But as the nerve root leaves the spine it gives up the protective fluid and passes laterally through an opening in the bones known as the vertebral foramen. A foramen is basically an opening within the body, and in this case, an opening between the vertebral bones.
Between each vertebrae is a disc. This disc is made out of a cartilage so that it has flexibility. Each side of the disc is connected to both the vertebrae above and below it. Without the flexible disc, we would not be able to bend (as bones don’t bend). This allows a tremendous amount of motion between the protective vertebrae. There are also several other ligaments that assist the disc in both keeping the bones together, but still allows movement in all 3 planes.
Now as the spinal nerve root exits the spinal cord deep within the spinal column, it changes direction from a vertical orientation to a horizontal one, in order to exit the foramen. Spinal nerves are always in pairs, and there is a right and a left one at each level of the spine. As they pass horizontally through the openings, they pass very close to the disc at that level that separates the vertebral bones.
We already mentioned that each disc is made up of cartilage. Inside the center of the disc is a very thick, gelatinous material known as the nucleus. The outside disc cartilage keeps the fluid in the center contained. A good analogy is a car tire. The outside rubber of the tire and steel belting underneath, keep the air of the tire contained. When you puncture through those protective layers, air can leak out.
It is the same with the disc. The outer layers are called the annulus fibrosus, and they keep the fluid contained inside the disc. When those annulus fibers get damaged, the pressure of the fluid inside can start to “bulge” the outer part of the disc (annulus) outward. We refer to this as bulging disc. When the annulus tears, it is called a herniation. This typically leads to the inside fluid (nucleus) squirting out in what we call a protrusion. These bulges and protrusions usually cause problems for the nerve roots that are passing by as they attempt to exit the vertebral foramen. This frequently causes not only back pain, but more frequently leg pain, numbness, tingling down to the feet and toes.
Now, back to what we discussed last week. When there is damage, irritation, disease, compression, or any problem with this part of the nerve root, we refer to it as a proximal peripheral neuropathy. These disc bulges/protrusions create one of the most common peripheral neuropathies in the body. We call it a radiculopathy. Many cases of leg pain, numbness, tingling, loss of muscle function in the foot or leg, or balance issues are caused by this proximal peripheral neuropathy. All of these symptoms may originate from the irritation or pinching of the nerve root at the back (or neck for symptoms in the hands, arms and fingers).
But why do some only have numbness? Or tingling? Why do I have pain only in my big toe and not the rest of my foot? And the number one question….why can someone have severe leg pain, numbness or tingling in the feet, but no back pain at all? Next week we’ll discuss this further.