Effects of Nerve Damage, or Nerve Root Impingement
Through research into the human spine, the 31 nerve roots, and the nerves branching off the main 31 nerves, we have been able to map the body to determine which nerves give which parts of the musculoskeletal system the ability to feel, sense touch, and move. Each nerve root and nerve supplies one particular section of the body bilaterally with the ability to feel, sense, and touch. We may be able to test the nerve function indirectly by looking at muscle strength, size, and skin sensations. For example, the detection of numbness or weakness in the legs indicates injury to either a section of the spinal cord, one of the nerve roots, or one of the nerves between L2 to S2. To get more specific information about spinal nerve root function, doctors may run a test known as lower body nerve evaluation.
Doctors may perform this test by running a device called a pinwheel along your skin, from your hips to your feet. While running this device along the skin, the doctor will continue asking the patient if he can feel the sift spikes of the pinwheel, and if there is a loss of sensation, or diminished sensation, along one area of the skin. A loss of sensation of one section of the leg may be indicative of nerve root impingement of one of the lumbar or sacral nerve roots. Let's take a look at dermatomes, and what the lower body nerve evaluation can tell us about the health of our spinal nerves.
Dermatomes. Dermatomes are the area of the skin supplied with nerve fibers by a single nerve root. So even though the 31 nerve roots do branch hundreds of times before they terminate in a specific body tissue, we are still able to trace back any loss of nerve sensation along the skin to a particular nerve root. There are 8 cervical nerve roots for the 7 cervical vertebrae. Otherwise, each of the thoracic, lumbar, and sacral vertebrae has a specific nerve root that supplied specific areas of the skin. Take a look at the following illustration. This illustration shows a map of the human body by dermatome section. For example, let's take a look at The section labeled L5 on the lower leg. L5 in this illustration runs on each side of the leg from about halfway up the side of the leg laterally inwards down to the middle of the front leg and foot. If during the lower body nerve evaluation test the patient reported either a heightened or diminished sensation on the bottom of the middle of the foot, it would indicate a nerve root impingement L5 spinal nerve root. The nerve coming from the fifth lumbar vertebrae (L5) supplied nerve function to a strip of skin along the lower back, the outside of the thigh, the inside of the lower leg, and the heel.
Nerve Root Disorders. There are 31 pairs of nerve roots, that project from each side of the spinal cord, and travel throughout the nervous system to each organ and tissue of the body. Each nerve root supplies information or sensation to a particular area of the body.