Lumbar Herniated Disc
If your doctor diagnoses your condition as a -bulging disc" or -disc bulge", you do not have a true disc herniation. A bulging disc is a diffuse outpocketing of the disc from the vertebral column, usually associated with some disc space collapse. A herniated disc or -slipped disc" refers to a focal defect within the outer wall of the disc, or annulus, allowing disc material (nucleus pulposus) to enter the spinal canal. Two percent of people in the United States have herniated discs accompanied by some type of symptom; however, a herniated disc does not always result in pain or disability. In fact, painful herniated discs account for only a small fraction of the larger population of low back pain patients. A lumbar disc herniation typically occurs between the ages of 30 to 50 years.
The structural integrity of a disc can be broken over time by wear and tear, loss of water with age, or by injury. With even a small degree of deterioration of the outer layer (annulus fibrosus), the soft inner core (nucleus pulposus) is able to push or bulge out from its normal constraints. This displacement putting pressure on a nearby nerve root and surrounding soft tissues is called nerve root impingement. The impingement causes irritation of the nerve root and can cause inflammation of the nerve and surrounding soft tissues. In turn, this leads to symptoms of sciatica, such as leg numbness, tingling, pain, and weakness. The general process of wear and tear may be accentuated in individuals who have a hereditary predisposition or physically demanding lifestyles. Intervertebral disc degeneration also characteristically results in the formation of vertebral osteophytes, or small bone spurs that can contribute to nerve impingement or spinal stenosis over time.
Figure 1: Lumbar disc herniation:
contained and noncontained
Lumbar disc herniations most commonly occur within the lowest two vertebral motion segments in the lumbar spine, lumbar vertebrae 4 to 5, and lumbar vertebra 5 to the first sacral vertebra. Several terms have been used to describe the degree to which a disc fragment -herniates" through its outer fibrous layer, known as the annulus fibrosus [Figure 1 ]. In a -contained" disc herniation the outer annular fibers are intact, although stretched over the protruding disc material. In a -noncontained" disc herniation, the disc material has broken through the annulus, thus having the potential for greater nerve root impingement. Two types of noncontained disc herniations include extruded disc herniations, where nucleus material has passed through a defect of an adjacent ligament (the posterior longitudinal ligament)but remains in continuity with the disc from which it came; and sequestered disc herniation where a piece of the herniated disc material has separated from the body of the disc and is not in direct continuity. Nerve roots can become entrapped between various formations of extruded material and abnormal bone formations present (osteophytes).
A herniated disc does not always cause painful or neurologic symptoms; in fact, only a small percentage do. So, although your doctor may find a disc showing signs of herniation from your imaging studies, that may not be the cause of your discomfort.
When symptoms are caused by a herniated disc, they will vary, depending on the patientês age and the size and location of the herniated disc fragment. Typically, a patient will have both back and radiating leg pain, numbness and tingling, and/or weakness of the lower extremities. Initially, only isolated low back pain may be present. Later, the pain typically extends into the buttock and leg and often to the foot. Leg pain may be sharp and stabbing with a sudden onset. Patients with herniated lumbar discs may find sitting particularly painful, may not be able to bend forward (flex the spine), may have an abnormal posture, or may lean to one side (called a list) from the muscles on one side of the spine being in a contracted state. Intolerance to driving a car or putting on socks in the morning are two common complaints. Physical examination may reveal a diminished response to light touch and temperature changes, loss of strength, or even a loss of deep tendon reflexes in the lower extremities.
Figure 2: Herniated disc with fragment
ccompressing the spinal nerves (MRI)
Your doctor will first perform a history and physical examination to look for evidence of the cause of your low back and leg symptoms, both functional and neurological (deep tendon reflexes, muscle testing, sensory exam). Should any of the findings suggest herniated disc, he will recommend imaging studies for confirmation. X-rays may be ordered to rule out other spinal structural abnormalities, but are not ideal for imaging herniated disc pathology. Advanced imaging studies, such as magnetic resonance imaging (MRI) [Figure 2 ] and computed tomography (CT) scans and myelograms are better to confirm the clinical suspicion of a disc herniation. MRI is the most commonly employed noninvasive diagnostic study.
Initial treatment for painful or symptomatic lumbar disc herniation includes short-term bed rest (1-3 days) with a support beneath the knees, nonsteroidal or steroid medication, pain medication (as necessary), and progressive ambulation. This treatment is followed by a back rehabilitation and fitness program. Aerobic conditioning and education are the most important factors in avoiding missed work days and returning to work quickly. If nonoperative treatments do not result in improved symptoms by six weeks then further evaluation and surgical consideration are warranted.
Failure of nonoperative treatment to control the symptoms of a herniated disc is the most common reason for surgical intervention. Surgery is indicated for severe sciatic pain (radiating leg pain) lasting for a minimum of six weeks and recurring episodes of sciatica. The acute massive disc herniation that causes bowel and bladder paralysis (cauda equina syndrome, see below) are best managed by immediate surgical excision of the disc to relieve nerve pressure. If there is evidence of progressive motor weakness, it is also best to intervene early with surgical intervention. The major benefit of surgical intervention for a herniated disc appears to be more rapid relief from sciatica pain than is provided by nonsurgical treatment.
The -gold standard" of surgical treatment for herniated discs is called a limited lumbar laminotomy and microdiscectomy. This entails a small midline incision (1-2 inches) in the lower back. Magnification using a microscope or specified magnification glasses is employed. Decompression of the compressed nerve root is achieved by removing the offending disc fragment(s) outside the disc as well as any other loose fragments within the disc. A radical, orcomplete discectomy, is not recommended, for this may lead to postoperative back pain and/or instability and has no proven success in decreasing the rate of recurrent disc herniations. A concomitant spinal fusion may be indicated for cases with preoperative severe back pain, revision discectomies requiring excessive bone removal, or preoperative instability. However, a fusion is rarely indicated for the initial discectomy, and serves more as a secondary salvage procedure (last resort surgical procedure for persistent symptoms).
Other surgical techniques sometimes employed for painful herniated discs include arthroscopic discectomy and percutaneous/laser discectomy. Arthroscopic discectomy is an accepted method of treatment that achieves decompression of the nerve root under direct visualization with an arthroscope. Percutaneous (aspiration of disc material by a probe) and laser discectomy have limited indications and there is currently no scientific evidence that supports their routine use.
Spontaneous resolution of symptoms from nerve root impingement due to a herniated disc occurs in 90% of all cases, most within the first 6 to 12 weeks. A typical bout of sciatica will improve spontaneously: symptoms improve in 50% of patients by one month, 90% by three months. Surgery has a very high success rate (>90 %) in improving the symptoms of herniated disc and allowing a return to work and normal activity. The relief of leg pain with surgical intervention is a much more predictable result (>90 %) than the relief of central back pain (>50 %).
Cauda equina syndrome is a set of symptoms typically caused by a large herniated disc that results in a high degree of nerve compression. Less commonly, cauda equina syndrome can be caused by spinal stenosis (see text below). In the lumbar spine, the spinal cord no longer has the shape of a single column; the nerve roots and nerves are spread out like a "horse's tail", hence the name "cauda equina", Latin for that term. Due to the common central position of the herniating disc to the cauda equina, symptoms are frequently bilateral.
Signs and symptoms of the cauda equina syndrome are low back pain, bilateral lower extremity weakness, bilateral nerve root pain (radiculopathy), perianal numbness, and bladder and bowel incontinence. These symptoms are a surgical emergency.
The confirming test for severe nerve compression causing cauda equina syndrome is MRI or CT-myelography.
The treatment of cauda equina syndrome is immediate surgical decompression of the compressed nerves via laminotomy or laminectomy and discectomy.