The spinal canal is like a tunnel which runs down the entire length of the spine from the skull to the sacrum (portion of the pelvis). This canal sits directly behind the bony blocks which make up the spine (vertebrae) and contains the nerves (spinal cord and nerve roots) running from the brain to all areas of the body. When something causes a narrowing of this canal then the nerves can become irritated or squeezed. This can lead to a variety of symptoms ranging from tingling, numbness, and weakness to severe pain and paralysis. Common conditions which can narrow the spinal canal include a herniated disc (often called a slipped disc), fracture of the spine, tumor, infection and degeneration (spinal stenosis).

The intervertebral disc is a complex spongy structure which consists of a central sticky gelatinous portion (nucleus pulposus) and an outer fibrous ring of tissue (annulus fibrosus). These discs are found along the entire spine from the neck all the way down to the lowest part of the back. The function of this disc is to permit motion of the spine while also acting as a shock absorber and a connecting link between the vertebrae. With aging this disc gradually looses some of its height and sponginess (decreasing water content). This explains partially why people shorten with aging. Young adults (20-45 years) are at risk for the disc to loose its normal structure and develop tears in the annulus fibrosus. Although injuries may cause disc problems, in many cases no direct trauma is responsible for disc problems.

When a disc begins to deform or a portion of the nucleus pulposus squeezes through a disc tear, then a bulge into the area of the spinal canal can develop. When a disc is noted to bulge into the area of nerves, this can lead to irritation of the nerves and is commonly called a "slipped disc". Nerve irritation may result from chemical irritation of the disc material in addition to compression from the disc itself. If an actual piece of disc separates off from the remainder of the disc and sits freely in the spinal canal, this is called a disc extrusion or sequestered disc fragment.

The symptoms from a disc herniation or extrusion will depend upon a number of factors including: size of disc herniation/extrusion, the location, the amount of room for the nerves, the time course?The type of symptoms can vary from numbness, tingling and pain (in arms or legs) to bladder and bowel dysfunction, weakness and even partial paralysis (in arms and legs). Treatment of a herniated disc must be individualized to each patient and is dependant upon the size and type of disc herniation as well as symptoms and degree of nerve irritation or dysfunction.

Most herniated discs will not cause severe problems and most symptoms will improve with time and do not require surgical treatment. Unfortunately, in a small group of patients the herniated disc continues to cause significant pain and disability. In those patients surgically removing the offending piece of disc material (a discectomy) can be very successful in removing pain. Prior to considering surgery a thorough examination and several test are essential to clearly identify the problem. Common tests include MRI, CT scan, myelogram and plain X-rays. A decision to operate should only be made after careful consideration of the different treatment options as well as the risks and benefits associated with the procedure. It should be noted that even in the best of hands, a severe nerve irritation due to a disc problem may cause permanent problems. Furthermore, after a discectomy, another portion of disc material may come out from the treated disc at some later time causing a recurrence of symptoms.

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