The term “stenosis” comes from Greek and means a “choking”. In lumbar spinal stenosis, the spinal nerve roots in the lower back are compressed, or choked, and this can produce symptoms of pain, tingling, weakness or numbness that radiates from the low back and into the buttocks and legs, especially with activity. Spinal stenosis in the neck can be far more dangerous by compressing the spinal cord itself and possibly leading to major body weakness or even paralysis. This is virtually impossible in the lumbar spine, however, as the spinal cord is not present in the lumbar spine.
In rare cases, lumbar spinal stenosis can be so advanced that it produces severe persistent disabling pain and even weakness in the legs. Most cases, however, have pain that radiates into the leg(s) with walking, and that pain will be relieved with sitting. This is called claudication which can also be caused by circulatory problems to the legs.
Spinal stenosis is related to degeneration in the spine and usually will become significant in the 5th decade of life and extend throughout every subsequent age group. Most patients first visit their doctor with symptoms of spinal stenosis at about age 60 or so. Patients need only seek treatment for lumbar spinal stenosis if they no longer wish to live with significant activity limitations, such as leg pain and/or difficulty with walking.
Spinal stenosis can occur in a variety of ways in the spine. Approximately 75% of cases of spinal stenosis occur in the low back (lumbar spine), which is called lumbar spinal stenosis, and mostly will affect the sciatic nerve which runs along the back of the leg. When this happens, it is commonly called sciatica.
Major types of stenosis include:
Central stenosis. A choking of the central canal, called central spinal stenosis in the lumbar (low back) area can compress the sack containing the horse’s tail (cauda equina) bundle of loose nerve filaments. Central spinal stenosis is more common at the second from the lowest lumbar spinal level and higher and is largely caused by a bulging of the disc margin plus a major overgrowth or redundancy of a ligament (ligamentum flavum) which is there to help protect the dura. This overgrowth is caused by segmental instability usually from a degenerating disc between adjacent vertebrae. The ligament arises from under the flat laminas of the vertebrae and the inside part of the facet joints (stabilizing joints located on each side at the back of the spine segments).
Foraminal stenosis. As the nerve root is about to leave the canal through a side hole (lateral foramen), a bone spur (osteophyte) that has already developed from a degenerating disc can press on that nerve root. This type of stenosis is also called lateral spinal stenosis. This is by far the most common form of spinal stenosis. 72% of cases of foraminal stenosis occur at the lowest lumbar level, trapping the emerging nerve root (which comprises a major part of the sciatic nerve).
Far lateral stenosis. After the nerve has left the spinal canal it can also be compressed beyond the foramen by either a bony spur protrusion or a bulging or herniated disc. When this happens, it is called far lateral stenosis.
These differences in anatomy may result in similar symptoms, which is why all forms of stenosis are typically referred to as simply ‘spinal stenosis’. However, if surgery is to be performed, the differences are very important in guiding the surgeon. That is, the bad spot(s) must be exactly known in advance to guide the approach for its proper treatment or removal.
