Author: Bryan Lang, PT, DPT, MHA, CSCS, Cert.DN: Doctor of Physical Therapy, Business Owner, Associate Professor, and Blog Contributor. Explores common client questions, helps find solutions for every day functional health concerns, and interprets difficult theories in healthcare rehabilitation. Committed to life-long learning and education. Learn more about Bryan on Google+.
If we didn’t have nerves, not only could we not move our muscles, but we also could not feel being touched. Therefore, if a nerve has been pinched or torn, one of the consequences can be numbness into the hand and other parts of the arm.
A nerve root is the initial segment of the nerve just after it branches off of the spinal cord and beings to pass through the spine to make its way out to the distant locations in our body. A nerve root can become pinched or torn.
Nerves have certain locations on our arms, forearms, and hands that they innervate to allow us to feel sensation in those areas. Researchers have mapped these spots and have helped medical professionals identify where there may be a damaged nerve based on the location of altered sensation on the arm and corresponding muscle weakness. Below are two tables showing sensation and muscle changes associated with different nerves:
Many people have heard of a disc bulge or a herniated disc when their friends are talking about their low back injuries, but herniated discs can occur in the neck, too. When there is a disc bulge, the structures that keep the liquid contents of the disc inside tear. The liquid then pushes out and compresses against any structures around it. Sometimes the disc will press against just one nerve root on one side of the body. In that case, the person will only feel their symptoms on that side of the body. Other times the disc can push into both nerve roots on the left and right side of the body. A person would then complain of issues in both of their arms and/or hands.
Image courtsey of http://physioworks.com.au/images/Injuries-Conditions/Bulging-Disc.jpg
Another common cause of nerve root injury and entrapment is from cervical spinal stenosis. As we age, we undergo a certain level of spinal degeneration. This occurs because we start to have excess movement in our spine due to decreased disc height between each vertebrae. If the spinal degeneration advances, excess bone will be created called bone spurs. As a bone spur enlarges, it narrows the spinal canal or the hole (foramen) that the nerve goes through before it leaves the spinal cord and travels out into the body. Eventually, the hole becomes so narrow that the nerve root is pinched, and numbness, tingling, pain, and decreased muscle strength can be the result [1].
Image courtesy of http://spinalstenosis.org/blog/wp-content/uploads/2011/12/foraminal-cervical-stenosis-diagram.jpg
References
[1] Cervical Spinal Stenosis. (2013, June 18). Retrieved July 24, 2015, from http://umm.edu/programs/spine/health/guides/cervical-spinal-stenosis