In rare cases, lumbar spinal stenosis can go no further than to produce 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, as discussed later in this article.
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 most will affect the sciatic nerve which runs along the back of the leg. When this happens, it is commonly called sciatica.
What is spinal stenosis? The vertebral column in the spine and sacrum (at the bottom of the spine) is like a stack of blocks that serve to support the structures of the body. Each of these bony structures has additional bony attachments that serve to help stabilize the spine and to protect the spinal cord or nerves passing downward from the brain to organs, muscles and sensory structures of the body. Each vertebral body and its attachments and the disc between the adjacent vertebrae are known as a spinal segment. The entire length of the spinal column has a large central canal or passage through which the spinal cord descends, and 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 are 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) 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).
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, or cauda equine) 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).
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.
Here's a GREAT video that explains it in very simple words.
So what, you may wonder. Well, this is me living with chronic pain. I go to massage therapy every week for relief and I thank God for my therapist. Back in 1986, I had major back surgery and had one disc removed along with bone spurs that had wrapped themselves around the sciatic nerve, touching it every time I moved. Have you ever gone momentarily blind from pain? Since 1986, my back has never been the same and I live day to day with some level of pain. The last time I had a CT scan (in 2004) it showed that I had "essentially unchanged multilevel spondylosis (spinal osteoarthritis) and interval progression of facet hypertrophy bilaterally at L4/5 and L5/S1." As my therapist works on me, we laugh as I joke about going to my "happy place" as the pain rises to a 10+ before it releases. I've learned to breathe through it and allow it to hurt because I know the relief will be so blessed. The next time I see my GP, I'm going to ask him if it might be wise to get another CT scan. After faithfully attending massage therapy for years and in the past two years losing over 50 lbs., pain levels haven't changed and I can only stand in one spot for a moment or two without losing the sensation in my left leg. One day as my friend and I were chatting with others after the church service, I suddenly realised that I couldn't feel either of my legs and had to excuse myself. Walking quickly over to the nearest seat, I almost fell into it and it took several minutes to get the feeling back.
Maybe in the 22 years since my original back surgery, they've come up with a far less invasion procedure to either fix this condition or at the very least minimize the pain. I know I'm not the only one who lives with this chronic suffering and I would do anything to stay on my feet and out of a wheelchair. Because of what I call my "invisible disability" I'm much more patient with strangers. We might "look" like we're normal (whatever that means), but who knows what each of us lives with in our daily lives.
Thus ends today's health lesson.