Low Back Pain Part II
Our spine's major function besides movement is to house and protect our spinal cord. Our spinal cord is a long bundle of nerves that forms the extension of our brain to the rest of our body. Nerves carry electrical impulses in the form of messages that our brain sends and receives allowing us to function. Our spinal cord branches off at each vertebral level, as well as at our sacrum and coccyx, to carry motor messages from our brain to our limbs for movement while also receiving information from every part of our body to be sent back to the brain for sensory input and balance. Our spinal cord and brain consist of our central nervous system (CNS) and when our nerves extend away from spinal cord they form our peripheral nervous system (PNS). As our nerves branch off to different parts of the body, they innervate different muscles which allow them to fire, innervate sections of our skin for sensory input from the external environment, and innervate organs so they know when and how to function. Some nerves can take a very long and winding path before arriving at their destination. For instance, the sciatic nerve travels and branches off multiple times starting from the bottom of our spinal cord and ending at our feet, innervating different body parts along the way. In fact, our spinal cord ends at around our second lumbar vertebra (L2), not L5, so the nerves that emerge after L2 have an even longer distance to travel. These nerves form a tail like structure called the cauda equina which hang down inside the rest of our spine and sacrum before exiting for their destination. Our nerves will weave in-between muscles, around bones, tendons, and cartilage, and sometimes go through muscles on their journey - allowing them many opportunities for dysfunction to occur.
As they leave the spine, nerves can become irritated or “pinched” by any of these connective tissues which can lead to pain, discomfort, inflammation, numbness, or tingling anywhere along the nerve tract as well as in the muscles and skin they innervate. The intravertebral discs that reside in-between our vertebral bodies are gel-like and provide our spine with cushioning that protect against the rigors of gravity and upright activity. These discs can become compressed over time for many reasons – lack of activity, poor diet, injury, etc. and can potentially herniate (get squeezed out) and put pressure on the nerve root exiting the spine. Usually the nerve will become compressed on one side of the spine leading to symptoms on that side of the body, but sometimes the protruding disc can put pressure on the spinal cord or cauda equina producing numbness or tingling in both legs. Nerves are most vulnerable just as they exit the spine through a hole called the intervertebral foramen (IVF), which leads out to the left or right side of the body. The IVF is a tunnel that can become constricted if a disc or joint between the vertebrae become compromised. Common reasons for the tunnel to constrict are a decrease in disc height, a vertebra becoming rotated due to a weak muscles, or a vertebral joint becoming inflamed. This will put pressure on the root of the nerve leading to pain or neurological symptoms in places that the nerve innervates. If this happens in the neck it may lead to symptoms in the hand but if it happens in the lumbar spine or sacrum/coccyx, you can issues in your feet. It is very important to align the spine and pelvis correctly if you have neurological symptoms in the lower extremities, and we do this by making sure that every muscle that is attached to these structures are strong and firing properly.