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Lumbar Disc Herniation
causes, symptoms, diagnosis and treatment for lumbar disc herniation
The disc (or intervetebral disc) is a structure that is found in between the spinal vertebral bodies from the neck to the sacrum (tailbone). The disc serves as a cushion and helps the spine to move. A single disc and its two vertebral bodies does not have much ability to move, however, when put together along the length of the spine, the amount of movement provided is considerable. Each disc is composed of two parts, the nucleus pulposus (the central part) and the annulus fibrosis (the outer part). The nucleus pulposus provides the padding and it is contained by the annulus fibrosis which forms a ring around the nucleus pulposus and also attaches to the vertebral bodies above and below.
Displacement of the disc material can occur centrally or more commonly, laterally. Lateral disc herniations are a frequent cause of sciatica (leg pain). This is called lumbar radiculopathy. The most common low back disc herniations are located between the 4th and 5th lumbar vertebral bodies and the 5th lumbar and 1st sacral vertebral bodies. These levels are also called L4/5 and L5-S1. These levels account for more than 90 percent of lumbar disc herniations. Although disc herniations can occur at the other lumbar spinal levels (L1-L2, L2-L3 and L3-L4) they are much less common than the two lower levels.
Radiologists and surgeons use a number of different terms when they refer to disc problems. Herniated disc, ruptured disc, protruded disc, prolapsed disc and slipped disc generally all mean the same thing. These terms imply that the nucleus pulposus has been displaced backwards and is pressing on a nerve root (or roots). Disc bulge refers to a general enlargement of the disc beyond its normal boundary. A disc bulge is not necessarily an abnormal finding and may simply be the result of aging. Similarly, the term disc degeneration (or degenerated disc) is often used, particularly in MRI reports. This means that there has been a loss of the fluid content of the disc and usually a loss of the normal disc height. Again, this is seen in normal aging. Although disc bulges and disc degeneration are seen in normal aging, they can both be associated with clinical problems.
Causes
Injuries are a frequent cause of lumbar disc herniations. Usually there is a history of heavy lifting associated with bending or twisting. Sometimes a fall or near fall with sudden violent motion of the spine can cause a disc herniation. Motor vehicle accidents and falls from a height can also cause disc herniations. It is not unusual for a patient to be unable to recall any specific injury.
Symptoms
The most common symptom of a lumbar disc herniation is pain. The pain is usually described as being located in the buttock with radiation down the back of the thigh and sometimes to the outside of the calf. The specific location may vary and depends on which disc is affected (and thus which nerve root is affected). The pain (and other symptoms and signs) come from pressure on the nerve root. The pain frequently starts as simple back pain and progresses to pain in the leg. When the pain moves to the leg, it is not unusual for the back pain to become less severe. Straining such as bowel movement, coughing or sneezing are all things that tend to cause the leg pain to worsen. Very large disc herniations may cause something known as the "cauda equina syndrome". This is a rare syndrome caused by a very large disc herniation putting pressure on many nerve roots. Signs and symptoms include urinary problems (either retention or incontinence), loss of leg or foot strength, "saddle" anesthesia (loss of sensation in the area of the body that would be in contact with a saddle), decreased rectal sphincter tone and variable amounts of pain (ranging from minimal to severe). This is a surgical emergency.
Diagnosis
As always, a careful history and physical examination are the first steps in diagnosis. A disc herniation at the L4-L5 level may cause decreased ability to bend the foot up at the ankle. There may also be loss of sensation involving the top of the foot, particularly towards the inside. A disc herniation at the L5-S1 level can cause difficulty pressing down with the foot and decreased sensation along the outside of the foot. In both cases, there may be pain when the leg is raised while the patient is laying flat. This is called the straight-leg raising test (also known as Lasègues sign). In the absence of indications for urgent intervention (loss of strength, urinary problems), imaging studies are probably not needed at the onset of pain. After a reasonable period of conservative (non-surgical) management if symptoms persist, an MRI is the best diagnostic test. Of interest is the finding that MRI in normal patients may show disc herniation in up to 36 percent of patients depending on the age of the patient. An MRI of the lumbar (or lumbo-sacral spine) will show most clinically significant disc herniations. In some rare cases MRI might not be diagnostic but points to a possibility. In these cases a myelogram and post-myelogram CT scan may be needed. Occasionally, electromyography and nerve conduction velocity testing (EMG/NCV) may be used to help distinguish between two possible nerve roots.
Treatment
The treatment of lumbar disc herniations can be divided into two categories, conservative (or non-surgical) and surgical. One exception would be in the cases of cauda equina syndrome, sudden loss of foot strength or urinary problems. In these cases, surgery would be considered the conservative approach!
In general, conservative management includes maneuvers to reduce pressure on the nerve root. Resting in a position with the hips and knees flexed often helps. Bed rest, however, should not last more than two to four days. During the acute phase of pain, lifting, bending, twisting and prolonged sitting should be avoided. Medication in the form of an anti-inflammatory such as aspirin, ibuprofen, naproxen, celebrex or vioxx may be taken. As these medications have side effects, patients should carefully read the package material or consult their doctor if taking any medications for longer than a few days. Braces or corsets are of little value and in the long term may cause a loss of muscle tone. If symptoms improve then a gradual resumption of normal activity follows. Other recommended treatments might include a short course of oral steroid medication, stronger pain medication, muscle relaxant medication, possibly steroids injected into the epidural (outside the covering of the nervous system) space. If pain relief is achieved, a course of physical therapy (or back school) can be useful to try to prevent recurrence by teaching proper body mechanics and spine musculature strengthening exercises.
Surgical treatment is reserved for patients who exhibit the signs and symptoms that require urgent decompression, patients who can not or do not wish to spend the time to allow conservative approaches to work and patients who have failed conservative management after a reasonable amount of time (six to eight weeks). The most commonly performed procedure for the treatment of lumbar disc herniation is known as lumbar discectomy (or micro-lumbar discectomy). The operation is usually done using a small incision (about an inch). Some form of magnified vision is used by the surgeon, either magnifying loupes (special glasses) or an operating microscope. Some patients may be able to go home the day of surgery. Most, however, stay for 24 to 48 hours. Some surgeons use an endoscope to perform discectomy. This allows for a smaller incision and less muscle dissection. The downside is that visualization and ability to remove some disc fragments may be compromised. Other techniques for treatment of disc herniation include percutaneous disc removal (mechanical or laser). These techniques are used much less frequently than standard discectomy.