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                                       Sciatica

Sciatic neuritis, sciatic neuralgia,or lumbar radiculopathy is a set of symptoms including pain caused by general compression or irritation of one of five spinal nerve roots of each sciatic nerve or by compression or irritation of the left or right or both sciatic nerves. Symptoms include lower back pain, buttock pain, and pain, numbness or weakness in various parts of the leg and foot. Other symptoms include a "pins and needles” sensation, or tingling and difficulty moving or controlling the leg. Typically, symptoms only manifest on one side of the body. The pain may radiate below the knee, but does not always.

Sciatica is a relatively common form of low back and leg pain, but the true meaning of the term is often misunderstood. Sciatica is a set of symptoms rather than a diagnosis for what is irritating the root of the nerve to cause the pain. Treatment for sciatica or sciatic symptoms often differs, depending on underlying causes and pain levels. Causes include compression of the sciatic nerve roots by a herniated (torn) or protruding disc in the lower back.

    

   

    

Definition

The term sciatica describes a symptom rather than a specific disease. Some use it to mean any pain starting in the lower back and going down the leg. Others use the term more specifically to mean a nerve dysfunction caused by compression of one or more lumbar or sacral nerve roots from a spinal disc herniation. Pain typically occurs in the distribution of a dermotome and goes below the knee to the foot. It may be associated with neurological dysfunction, such as weakness. The pain is characteristically of shooting type, quickly traveling along the course of the nerve.

Causes

Spinal disc herniation

Main article: Spinal disc hemiation

Spinal disc hemiation pressing on one of the lumber or sacral nerve roots is the primary cause of sciatica, being present in about 90% of cases.Sciatica caused by pressure from a disc herniation and swelling of surrounding tissue can spontaneously subside if the tear in the disc heals and the pulposus extrusion and inflammation cease.

 

Spinal Stenosis

Main article: Lumber spinal stenosis

Other compressive spinal causes include lumber spinal stenosis, a condition in which the spinal canal (the spaces the spinal cord runs through) narrows and compresses the spinal cord, cauda equina, or sciatic nerve roots. This narrowing can be caused by bone spurs,spondylolisthesis, inflammation, or hrmiated disc, which decreases available space for the spinal cord, thus pinching and irritating nerves from the spinal cord that travel to the sciatic nerves.

 

Piriformis syndrome

Piriformis syndrome is a controversial condition that, depending on the analysis, varies from a "very rare" cause to contributing to up to 8% of low back or buttock pain. In 15% of the population, the sciatic nerve runs through, or under the piriformis muscle rather than beneath it. When the muscle shortens or spasms due to trauma or overuse, it's posited that this causes compression of the sciatic nerve. It has colloquially been referred to as "wallet sciatica" since a wallet carried in a rear hip pocket compresses the buttock muscles and sciatic nerve when the bearer sits down. Piriformis syndrome cause sciatica when the nerve root is normal.

 

Pregnancy

Sciatica may also occur during pregnancy as a result of the weight of the fetus pressing on the sciatic nerve during sitting or during leg spasms. While most cases do not directly harm the fetus or the mother, indirect harm may come from the numbing effect on the legs, which can cause loss of balance and falling. There is no standard treatment for pregnancy induced sciatica.

 

Other

Sciatica can also be caused by tumours impinging on the spinal cord or the nerve roots. Severe back pain extending to the hips and feet, loss of bladder or bowel control, or muscle weakness may result from spinal tumours or cauda equina syndrome. Trauma to the spine, such as from a car accident, may also lead to sciatica.

 

Pathophysiology

Sciatica is generally caused by the compression of lumber nerve L3, L4, or L5 or sacral nerves S1, S2, or S3, or by compression of the sciatic nerve itself. When sciatica is caused by compression of a dorsal nerve root (radix), it is considered a lumbar radiculopathy (or radiculitis when accompanied with an inflammatory response). This can occur as a result of a spinal disk bulge or spinal disc hemiation (a herniated invertebral disc), or from roughening, enlarging, or misalignment  (spondylisthesis) of the vertebrae, or as a result of degenerated discs that can reduce the diameter of the lateral foramen (natural hole) through which nerve roots exit the spine. The intervertebral discs consist of an annulus fibrosus, which forms a ring surrounding the inner nucleus pulposus. When there is a tear in the annulus fibrosus, the nucleus pulposus (pulp) may extrude through the tear and press against spinal nerves within the spinal cord, cauda equina, or exiting nerve roots, causing inflammation, numbness, or excruciating pain. Inflammation in the spinal canal can also spread to adjacent  facet joints and cause lower back pain and/or  referred pain in the posterior thigh(s). Pseudo sciatic pain can also be caused by compression of peripheral sections of the nerve, usually from soft tissue tension in the piriformis or related muscle.

The spinal discs are composed of a tough spongiform ring of cartilage (“annulus fibrosis ) with a more malleable center (“nucleus pulposus”). The discs separate the vertebrae, thereby allowing room for the nerve roots to properly exit through the spaces between the vertebrae. The discs cushion the spine from compressive forces, but are weak to pressure applied during rotational movements. That is why a person who bends to one side, at a bad angle to pick something up, may more likely herniate a spinal disc than a person jumping from a ladder and landing on their feet.

Herniation of a disc occurs when the liquid center of the disc bulges outwards, tearing the external ring of fibers, extrudes into the spinal canal, and compresses a nerve root against the lamina or pedicle of a vertebra, thus causing sciatica. This extruded liquid from the “nucleus pulposus” may cause inflammation and swelling of surrounding tissue, which may cause further compression of the nerve root in the confined space in the spinal canal.

 

Diagnosis                    Sciatica is typically diagnosed by physical examination, and the history of the symptoms. Generally if a person reports the typical radiating pain in one leg as well as one or more neurological indications of nerve root tension or neurological deficit, sciatica can be diagnosed.

The most applied diagnostic test is the straight leg raise to produce Lasegue sign, which is considered positive if pain in the distribution of the sciatic nerve is reproduced with between 30 and 70 degrees passive flexion of the straight leg. While this test is positive in about 90% of people with sciatica, approximately 75% of people with a positive test do not have sciatica.
Imaging tests such as computerized tomography or magnetic resonance imaging can help with the diagnosis of lumbar disc herniation. The utility of MR neurography in the diagnoses of piriformis syndrome is controversial.

 

Management

When the cause of sciatica is lumber disc hermation, most cases resolve spontaneously over weeks to months. Initially treatment in the first 6–8 weeks should be conservative. There does not appear to be a significant difference in outcomes between advice to stay active and recommendations of bed rest. Similarly, physical therapy (exercises) has not been found better than bed rest.

 

Medication

Although medicines are commonly prescribed for the treatment of sciatica, evidence for analgesics is poor. Specifically, NSAIDs do not appear to improve immediate pain and all NSAIDs appear about equivalent.  Evidence is also lacking in use of opioids and muscle relaxants. In those with sciatica due to piriformis syndrome, botulism toxin injections may improve pain and or function.

 

Surgery

Surgery for unilateral sciatica involves the removal of part of the disc, known as a discectomy. While it results in short term benefits, long term benefits appear equivalent to conservative care. Treatment of the underlying cause of the compression is needed in cases of epidural abscess, epidural tumors, and cauda equina syndrome. .

 

Epidurals

Good quality of evidence to suggest short-term pain reduction with epidural steroid injections, long-term benefit is controversial. Other agents, ex: TNF inhibitors, have not shown efficacy in most randomized controlled trials.

 

Alternative medicine

Moderate quality evidence suggests that spinal manipulation is an effective treatment for acute sciatica. For chronic sciatica the evidence is poor. Spinal manipulation has been found generally safe for the treatment of disc-related pain; however, case reports have found an association with cauda equina syndrome  and it is contraindicated when there are progressive neurological deficits. 

 

Epidemiology

Depending on how it is defined, 1.6% to 43% of people have sciatica.