Spinal stenosis introduction
The term “stenosis” comes from Greek and means a “choking”. In lumbar spinal stenosis, the spinal cord or spinal nerve roots are compressed, or choked, and this can produce symptoms of pain, tingling, weakness or numbness that radiates into the buttocks and legs.

When nerves are compressed they can produce symptoms of pain, numbness and tingling into the legs with activity. In rare cases, it can produce severe pain and even weakness. Most cases will produce pain into the legs with walking, and the pain will be relieved with sitting.

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.

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), and most will affect the sciatic nerve which runs along the back of the leg.

What is spinal stenosis?
The skull, vertebral column in the spine and sacrum (at the bottom of the spine) serve to support the structures of the body and to protect the delicate brain, spinal cord and nerves beneath. Each of these bony structures has holes through which nerves pass outward to the major parts of the body.

The entire length of the spinal column has a large central canal or passage through which the spinal cord descends, and then secondary holes to each side of the canal to allow emergence of spinal nerves at each level. The spinal cord stops at the upper part of the low back, and below that the tiny contained nerve rootlets descend loosely splayed out - like a horse’s tail – and protectively enclosed in a long sack. All central nerve structures are protected further by membranes, with a tough outer membrane called the dura (tough) mater (mother).

Major types of stenosis include:

• Foraminal stenosis. As the nerve root is about to leave the canal through a side hole (lateral foramen), a bone spur (osteophyte) can press on the nerve root. This type of stenosis may also be 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 (a major part of the sciatic nerve).

• Central stenosis. A choking of the central canal, called central spinal stenosis in the lumbar (low back) area can compress the sack of the horse’s tail (cauda equina, or cauda equine). Central spinal stenosis is more common at the second lowest lumbar spinal level and above and is largely caused by redundancy of a ligament (ligamentum flavum) which is associated with protecting the dura and arises from the inside part of the facet joint.

• Far Lateral stenosis. After the nerve has left the spinal canal it can also be compressed on the outside of the spine from either a bony protrusion or disc bulge.

These differences are not particularly important from a clinical symptom point of view, 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 surgery. That is, the bad spot(s) must be exactly known in advance to guide the approach for its removal.