Conquer Back and Neck Pain - Walk It Off! (19 page)

How constricted does the spinal canal become? The size of the normal spinal canal in your low back can be pictured by making a circle with your thumb and index finger the diameter of a quarter. Now decrease the size of the circle to the diameter of a pencil to illustrate severe spinal stenosis. Picture all of the nerves for the muscles and the sensation in your legs as well as for your bowel, bladder, and sexual function going through the normal quarter-sized-diameter spinal canal, with some room to spare. Then picture these nerves being squeezed into a spinal canal the diameter of a pencil, with no room at all to spare. That is severe spinal stenosis. A combination of bulging of the disc, thickening of the spinal ligaments, and arthritic enlargement of the facet joints and vertebrae (osteophytes, or “bone spurs”) can constrict the spinal canal to the diameter of a pencil, thus preventing oxygen from reaching the spinal nerves.

The normal diameter of the spinal canal on the low back is the size of a quarter, whereas the severely constricted spinal canal from spinal stenosis is the diameter of a pencil.

Your spinal nerves can withstand a lot of compression if it is applied slowly and evenly. Therefore they can be squeezed pretty tightly before they become painful. However, as you walk the nerves normally glide back and forth in your spinal canal. This gliding action is restricted as the spinal canal becomes tighter. Because the spinal nerves cannot glide normally, they become irritated and swell up, taking up even more room in an already tight spinal canal. This, in turn, causes the nerves to produce pain impulses that are perceived by the brain to be from your legs.

You should suspect spinal stenosis in your low back if you have aching pain in your legs brought on by walking and relieved by sitting (neurogenic claudication). The pain may be localized to your back, or it may radiate from your back to one or both legs, buttocks, thighs, even as far as your calves and your feet. The symptoms of spinal stenosis in your back may be pain in any combination of the locations mentioned above, depending on the level(s), degrees of constriction, and sites of the spinal stenosis. At each of the five discs in your low back there are five sites at which constriction can take place. Spinal stenosis in the central spinal canal causes classic aching pain in the front and back of your thighs and calves.

This patient-generated pain drawing depicts pain from spinal stenosis in the back of the legs and front of the thighs (symbol for aching is + sign) and pain from poor circulation in the calves (symbol for burning is the X sign).

At each disc level in your spine, the nerve channels can be constricted at two locations on each side, as well as in the spinal canal itself. On either side of your spinal canal the nerves can be squeezed where they begin to exit the spinal canal (lateral recess stenosis, see illustration on page 71), in the channel through which the nerve exits the spinal canal (foraminal stenosis). Therefore there are 25 possible sites at which the nerves to your legs can be entrapped by spinal stenosis, in your low back alone!

More often than not, by the time you develop symptoms from spinal stenosis, the nerves are being squeezed at more than one site at the same time. I will explain how we determine exactly where the pain is coming from later in this chapter.

The classic symptoms of spinal stenosis — aching in the legs with walking that is relieved by rest (neurogenic claudication) — can be confused with the symptoms caused by poor circulation in your legs (vascular claudication). If you have poor blood circulation in your legs, walking may cause aching in your legs that is relieved by rest, very similar to the symptoms seen with spinal stenosis, but with some important differences. When the muscles in your legs do not get enough oxygen because of poor circulation, they produce lactic acid with activity. Lactic acid produces cramping pain in the muscles (see figure page 74).

There are some subtle differences in symptoms between the pain from spinal stenosis and poor circulation. Pain from spinal stenosis usually begins in the low back and radiates into the leg(s) and is relieved by sitting or bending over; both maneuvers open up the spinal canal, thus relieving the pressure on the nerves. Patients are frequently confused by the symptoms of spinal stenosis because their walking is limited by leg pain but they are still able to bicycle, dance, or lean on a shopping cart and get around without pain. All of these postures allow the person to bend forward enough to open up the spinal canal, relieving the pressure on their spinal nerves. When you see someone who is having difficulty walking because of spinal stenosis, they usually walk in a characteristic bent-forward position. Patients with spinal stenosis will tell you that they have good days when they can walk unlimited distances and bad days when their walking is very limited.

The symptoms of poor circulation to the legs start as a cramping sensation in the calves and radiate proximally upward into the whole leg. The pain is not relieved by bending forward. The symptoms progress with physical activity as the lactic acid in the oxygen-starved muscles builds up. The person experiencing these symptoms would rather stand than sit for relief because blood flow to the legs is stronger while standing than sitting. They cannot walk, bicycle, dance, or take part in any physical activity without developing muscle pain. The symptoms of vascular claudication are the same every day.

Spinal stenosis and poor circulation to the legs is more common after the age of 60 and can occur simultaneously, so it is possible to have symptoms of both conditions at the same time. I have seen patients who could clearly describe to me the symptoms of both. I can advise these folks which symptom is coming from which condition, and then determine from them which pain they more urgently want to be relieved of. Most people can tolerate vascular claudication better than neurogenic claudication and want their spinal stenosis fixed first. However, your PCP should refer you to a vascular surgeon to help you decide whether to pursue surgery for vascular claudicaton.

Sciatic leg pain from a herniated disc can sometimes be confused with pain from spinal stenosis. It is important to distinguish which condition the symptoms stem from because herniated discs will usually shrink with time and the pain will resolve on its own, whereas the symptoms from spinal stenosis may gradually become worse over time and eventually require surgery for relief. Disc herniations, as you will recall from
Chapter 5
, produce pain by compressing, stretching, and chemically irritating the spinal nerve. Leg pain from a herniated disc usually radiates along the course of a spinal nerve and is present even at rest. In contrast, the pain from spinal stenosis radiates over the course of more than one nerve and is relieved by sitting or bending over. The ability to bend over at the waist while standing and to lift the symptomatic leg up while lying face up is limited by a herniated disc. Bending and straight-leg raising are not limited and in fact may relieve the pain from spinal stenosis.

A disc herniation may contribute to spinal stenosis, particularly when it occurs in the lateral recess or foramen of the spinal canal. This can happen when a disc herniation occurs in a small or misshapen spinal canal. The normal spinal canal is triangular in shape and the diameter of a quarter. Approximately 10 percent of people are born with a cloverleaf-shaped spinal canal that approaches the size of a nickel or smaller. This is called congenital spinal stenosis. Smaller degenerative changes in the disc and facet joints may result in more significant encroachment on a misshapen or small spinal canal than they would on a normally shaped and sized spinal canal. This is particularly true in the lateral recess, that area on the side of the spinal canal where the nerves just begin to enter the channel to exit the canal. A small disc bulge or herniation in a congenitally small lateral recess may result in severe leg pain, whereas it would cause no symptoms in a normal lateral recess. Lateral-recess stenosis with a disc herniation may cause a combination of the classic symptoms and physical findings seen with either condition alone.

A typical symptom of lateral-recess stenosis is leg pain with rotation of the spine, such as at the end of a golf swing. I once operated on a famous professional golfer who had pain at the end of her golf swing that was seriously affecting her ability to compete. I performed a surgical decompression of one lateral recess and she was able to continue playing on the international circuit. I took care of a college soccer player who had sciatic leg pain when he kicked the ball. He had spinal stenosis localized to one lateral recess. I surgically decompressed his lateral recess and he went on to become a professional player in Europe.

Constriction of the spinal canal can result from conditions other than disc degeneration, congenital small canal, and disc herniation. Cysts can form on degenerated facet joints similar to the cysts that form on arthritic finger joints. They are called facet-joint cysts or synovial cysts of the facet joint. These cysts can cause spinal stenosis and produce aching symptoms in the legs. They usually occur in the lumbar spine, but I have seen them in the cervical and thoracic spine as well. They are benign, not cancerous, and rarely recur after they are surgically removed.

Paget’s disease is a condition that causes bones to thicken and joints to become arthritic. Paget’s disease can involve the vertebrae, facet joints, and lamina of the spine, resulting in a severe form of spinal stenosis.

This MRI scan of the low back, side view, shows the spinal canal that has been constricted (spinal stenosis) by a bulging disc, slippage of the spine, and a facet joint cyst. There are two other herniated discs (HNP), one large and one smaller. It is unusual to see all of these conditions in the same patient.

Very slow-growing benign tumors of the nerves inside the spinal canal (neurofibroma, schwannoma) can constrict the space for the remaining nerves and cause symptoms typical of spinal stenosis. However, these tumors are usually associated with progressively severe night pain that disturbs normal sleep patterns. Although most people have night pain with spinal stenosis, it is relieved by certain positions, such as sleeping on your side with your legs curled up.

Some small people, such as those born with achondroplasia, can have an extremely small spinal canal and develop the symptoms of spinal stenosis as early as in their teens.

The symptoms of spinal stenosis in the upper lumbar spine between the first, second, and third lumbar discs can be confused with symptoms coming from an arthritic hip or knee joint. Since spinal stenosis most commonly occurs in the age groups who suffer from arthritis of these joints, symptoms can be coming from the spine and joint arthritis at the same time. I published a study of the symptoms of 97 patients who had symptoms of spinal stenosis alone, symptoms of hip arthritis alone, or symptoms of spinal stenosis and hip arthritis together. The study showed that if you have groin pain and a limp with loss of motion in the hip, you are more apt to have hip arthritis. If you have a positive femoral-stretch test, which means you have pain in the front of your thigh when you bend your knee while lying on your stomach, you are more likely to have spinal stenosis. A combination of these findings would suggest that both conditions are symptomatic at the same time.