What is Spinal Stenosis?
A clue to answering this question is found in the meaning of each word. Spinal refers to the spine. Stenosis is a medical term used to describe a condition where a normal-size opening has become narrow. Spinal stenosis may affect the cervical (neck), thoracic (chest), or lumbar (low back) spine. The most common area affected is the lumbar spine followed by the cervical spine.

Are there particular spinal structures that are affected?
Yes. To help you to visualize what happens in spinal stenosis, we will consider a water pipe. Over time rust and debris builds up on the walls of the pipe thereby narrowing the passageway that normally allows water to freely flow. In the spine, the passageways are the spinal canal and the neuroforamen. The spinal canal is a hollow vertical hole that contains the spinal cord. The neuroforamen are the passageways that are naturally created between the vertebrae through which spinal nerve roots exit the spinal canal. See Figure 1.

Figure 1.
The spine's bony structures encase and protect the spinal cord. Small nerve roots shoot off from the spinal cord and exit the spinal canal through passageways called neuroforamen.

Figure 2 is an artist's illustration of lumbar spinal stenosis. Notice the narrowed areas in the spinal canal (reddish-colored areas). As the canal space narrows, the spinal cord and nearby nerve roots are squeezed causing different types of symptoms. The medical term is nerve compression.

Figure 2. Lumbar spinal stenosis.