SPINAL STENOSIS

WHAT IS SPINAL STENOSIS?

Spinal stenosis means “narrowing of the spine”. At the back of each vertebra is a tunnel through which the spinal cord and nerves run down the spine (the spinal canal); between each pair of vertebrae the nerves which branch off from the cord run out through a gap ( the intervertebral foramen). If the spinal canal or intervertebral foramen becomes too narrow, the cord or nerves can be compressed, preventing them working normally.

WHAT CAUSES SPINAL STENOSIS?

The most common cause of narrowing is degeneration of the spine (a form of arthritis). When this happens, the discs and joints between the vertebrae wear out and bulge into the canal and foramen, taking up space needed by the nerves. Some people are born with a narrow canal, and their nerves can be compressed if only a little additional narrowing takes place. If degeneration is severe, or if the spine is injured, the vertebrae can slip out of position, and cause nerve compression.

VERTEBRA SEEN FROM ABOVE
VERTEBRAE SEEN FROM THE SIDE
SPINAL STENOSIS WITH NARROWED CANAL
SPINAL STENOSIS WITH A NERVE COMPRESSED IN THE FORAMEN


HOW DOES SPINAL STENOSIS CAUSE PROBLEMS?

When the cord or nerves are compressed they are unable to work; this causes weakness of the muscles, and loss of feeling and “pins and needles” in the parts of the arms or legs that they supply. This is often felt as a lame or dead feeling.
Pain may be caused by the nerves being squeezed, but also by the degeneration of the spine, and it may be necessary to treat both problems to relieve all the symptoms.
Often the patient is only affected when standing or walking, and he feels relief if he bends forward, sits or lies down.
Rarely, the nerves supplying the bladder and bowels can be affected and lead to poor control, with incontinence of urine or faeces.

IS SPINAL STENOSIS DANGEROUS?

It is rare for spinal stenosis to cause paralysis. If this does happen, it usually follows a neck injury (such as a fall), where the spinal cord in the narrowed part of the spinal canal is squashed and damaged, perhaps permanently.

HOW DO I KNOW IF I HAVE SPINAL STENOSIS?

Often the diagnosis is made from the patient’s symptoms when he describes them to the doctor. In some cases there are signs of abnormal nerve function when the patient is examined.
Normal X-rays do not show nerves or discs, only the bony part of the spine, so they are not enough for a definite diagnosis. The diagnosis is confirmed by an MRI scan, or a CT scan after a myelogram (injection of dye into the spinal canal by a lumbar puncture), which shows the narrowing of the canal, and the compression of the nerves.

IF I HAVE SPINAL STENOSIS DOES THAT MEAN AN OPERATION?

Not at all. Most patients stay the same, or get slowly worse, with only about 10% worsening rapidly. Many patients can live with their symptoms, once they know what causes them, with help from physiotherapy, weight loss, anti-inflammatory drugs and pain medicines. Often a corset helps for low back problems, or a neck brace for the neck. Pain blocks with cortisone may also help.

Surgery may be needed if the pain is severe and does not improve with treatment, or if there is severe nerve compression, shown by difficulty with bladder control, walking even short distances or doing other basic tasks.

Surgery is often performed earlier if -the stenosis is in the neck, as the cord is more easily damaged than in the lower back, -if the vertebrae have slipped out of position, as this may get worse and increase the nerve compression, or -if the patient is diabetic, as the nerves once damaged do not recover as well as in normal patients.

WHAT DOES THE OPERATION INVOLVE?

During the operation, bone and ligaments are removed to open up the spinal canal and foramen to make space for the nerves. This operation is called a decompression. This is usually done from behind in the lower back, and is called a laminectomy. A laminectomy may also be done in the neck if more than two levels need to be decompressed, but if only one or two levels are narrowed, decompression is usually done through the front of the neck. A decompression may need an additional operation to fix the decompressed vertebrae together in some patients; this operation is called a fusion. Bone is packed between the vertebrae, so that they grow together permanently to form a single piece of bone. Often metal plates or rods are fixed to the spine with screws to hold everything in place until the bone has healed. It is not usually necessary to remove this fixation. A fusion is usually needed if the vertebrae have already slipped, or are expected to slip after the operation, or if the spine is deformed or so badly worn or arthritic that it is expected to continue to cause pain even though the nerves have been decompressed. A neck decompression almost always needs a fusion.

LAMINECTOMY VIEWED FROM THE BACK OF THE SPINE

LAMINECTOMY SEEN FROM ABOVE TO SHOW HOW THE CANAL IS ENLARGED


HOW SUCCESSFUL ARE THE OPERATIONS?

About 80% of patients are relieved for 5 years or more. Spinal stenosis is a problem of older people, so some patients will develop problems at new levels because we cannot stop them and their spines getting older, and these people may need further operations. For the same reason, it is unusual for the patient to have a normal, painless back or neck after these operations The aim of surgery is to improve the problem, even if it cannot be completely relieved.

COULD THE OPERATION MAKE ME WORSE?

All operations have a risk of complications, and these are delicate operations which take time, often with loss of blood. Many patients are old, with other diseases which make the anaesthetic and surgery risky, possibly even fatal. Nerve damage with partial or complete paralysis is rare (less than 0,05%) but can occur, mainly in neck operations. Leakage of the fluid round the nerves can follow a tear of the lining of the canal, even if it is repaired. Blood clots in the legs (deep vein thrombosis – DVT ) may cause swelling of the legs, and may break free and pass up into the lungs causing death. Wound infections occur in 1 or 2% of operations, and may be difficult to treat. Blood transfusion can be complicated by reactions, or transmission of disease from the donor. There are many other possible complications, although they are rare. The risk of most of these complications can be reduced by taking certain precautions. If you are thinking about an operation you should speak to your doctor about the risks in your specific case, and what can be done to limit them

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