Sciatica is a sensation of leg pain, weakness, numbness or tingling that originates from a sciatic nerve. The two sciatic nerves each run from the lower back through the hip and buttock and down the back of the leg. They control many of the muscles in the lower legs, as well as feeling in parts of the thighs, legs and feet.

Sciatica is the result of compression or other damage to one or both sciatic nerves. The many causes of sciatica include herniated discs, spinal stenosis, degenerative disc disease, spinal arthritis, muscle spasms, pregnancy, physical trauma and impaired circulation.

The pain that accompanies sciatica can range from mild to excruciating. In severe cases, patients have described the pain as being similar to that of an electric shock. Milder forms can often be treated with over-the-counter anti-inflammatory medications or cold and heat treatments. However, some cases require professional medical care such as prescription medications, physical therapy, injection therapy or surgery.

Sciatica is pain radiates along one or both of the sciatic nerves, the longest nerves in the body. Symptoms include tingling, numbness or muscle weakness that can range from mild to severe and incapacitating. Many people with sciatica feel pain when they sit, sneeze or cough. Sciatica can affect both sides of the lower body - including the lower back, buttocks, legs and feet - but usually affects only one side.

Sciatic nerve roots originate from the spinal cord in the lower back and run from one side of the pelvis through the hip and buttocks and down the back of the leg. These two nerves control many of the muscles in the lower legs, along with sensation in parts of the thighs, legs and feet. Each sciatic nerve branches at the knee into the tibial and peroneal nerves.

Sciatica is a form of peripheral neuropathy, which involves damage to the peripheral nervous system (nerves outside the central nervous system, which consists of the brain and spinal cord). This system is the communications network that transmits information between the central nervous system and other parts of the body.

Most often, a herniated disc in the lower back compresses the spinal nerve roots that combine to form the sciatic nerve. This triggers pain that can range from mild to severe in intensity. However, other factors can also cause sciatica, including:

• Degenerative conditions such as spinal stenosis (narrowing of the spinal canal), degenerative disc disease or spinal arthritis
  
  
• Prolonged external pressure on the nerve
  
  
• Pressure on the nerve from nearby structures, such as a tight muscle or a pregnant woman's growing fetus
  
  
• Physical trauma such as a pelvic fracture
  
  

All these factors can cause pressure over the nerve, but inflammation of the nerve is required to cause pain in the back or leg.

Sciatica typically affects people between the ages of 30 and 50. Between 80 percent and 90 percent of people with sciatica get better over time without having to resort to surgery, according to the American Academy of Orthopaedic Surgeons.

Sciatica may be caused by the compression of a nerve root in the lower (lumbar) spine, a condition known as radiculopathy. The most common cause of such a compression is a herniated disc in the lower back.

The intervertebral discs are pads made up of cartilage that separate the spinal bones (vertebrae). Each disc contains a jelly-like substance surrounded by a tough, fibrous covering. When this covering tears because of injury, illness or deterioration due to aging, it can allow the jelly-like interior to seep out or rupture. This substance can then cause pressure and swelling of the nerve root, causing back pain or leg pain that is often excruciating.

When a damaged disc is located in the lower part of the back, it may cause numbness, tingling or weakness in the buttock, leg or foot.

In addition to herniated discs, other conditions can also pressure the sciatic nerve. These include:

• Spinal stenosis. A condition in which one or more areas of the spinal canal narrow, causing pressure to build on the spinal cord or on the roots of nerves that branch off from the spinal cord. When this narrowing occurs in the lower spine, the lumbar and sacral nerve roots are sometimes affected, potentially resulting in sciatica.
  
  
• Degenerative disc disease. Age-related condition in which the intervertebral discs wear down, causing compression of sciatic or other spinal nerve roots.
  
  
• Spondylolisthesis. Occurs when a vertebra slips slightly forward over another vertebra. The displaced bone may pinch a sciatic nerve at the point where it leaves the spine. Causes of spondylolisthesis include degenerative disc disease and spondylolysis, a type of stress fracture in a lumbar vertebra that is common in school-age athletes.
  
  
• Pregnancy. The growing fetus can press against one or both of the mother’s sciatic nerves.
  
  
• Piriformis syndrome. Disorder where the piriformis muscle (which runs directly above the sciatic nerve) becomes tight or spasms, putting pressure on the sciatic nerve. Runners and walkers most often develop the condition, which can also be caused by prolonged sitting, car accidents and falls.
  
  
• Trauma. Accidents, falls or blows to the spine can injure lumbar or sacral nerve roots, resulting in sciatica. Other sources of trauma that may cause sciatica include pelvic fractures; nerve damage accidentally inflicted during injections to the buttocks, surgery or other medical treatments; gunshot wounds; or other trauma to the buttocks or thighs. Another potential cause of pelvic or spinal fractures is osteoporosis.

• Arthritis in the back, such as spinal osteoarthritis (spondylosis) or ankylosing spondylitis.
  
  
• Spinal tumors. Tumors – masses of abnormal cells – can occur inside the spinal cord, within the membranes that cover the spinal cord or in the space between the spinal cord and the vertebrae. Benign (noncancerous) or malignant tumors can compress the spinal cord itself or the nerve roots, resulting in severe back pain, hip pain, leg pain or foot pain. Other symptoms include muscle weakness or loss of sensation, difficulty walking (gait disturbances) and loss of bladder or bowel function.
  
  
• Impaired circulation. Conditions that decrease the blood supply (e.g., peripheral arterial disease) to the sciatic nerves can spark sciatica.
  
  
• Spinal abnormalities. Anatomical irregularities such as scoliosis (a sideways bending of the spine) may cause impingement of a sciatic nerve.
  
  
• Sciatic nerve tumor or injury. In rare situations, the sciatic nerve itself may be affected by a tumor or trauma. This can result in sciatic pain.
  
  
• Other causes. In some cases, it may be difficult to find the source of sciatic pain. Problems affecting the bones, joints and muscles can all potentially cause sciatic pain.

In addition, certain factors may raise the risk of sciatica for some people. These include:

• Age. Most people have some deterioration in their intervertebral discs by the time they are 30, and herniated discs are most likely to occur in a person’s 40s or 50s. One of the leading causes of sciatica – spinal stenosis – primarily occurs in people who are 50 and older.
  
  
• Job. People who work in occupations that require them to twist their backs, carry heavy loads or drive for hours at a time are at increased risk for sciatica.
  
  
• Sedentary lifestyle or some forms of exercise. People who sit for long periods of time or who live sedentary lifestyles are more vulnerable to sciatica than those who exercise regularly. Prolonged sitting or lying with pressure on the buttocks is particularly likely to trigger symptoms. Some forms of exercise, such as jogging, may increase the risk of sciatica for some people. Patients should consult their physician about the most appropriate exercise regimen.
  
  
• Genetic factors. Genetics may predispose some people to having disc problems, which can lead to sciatica.
  
  
• Diabetes.  Patients who have this condition, a disorder in how the body uses glucose (blood sugar), are more likely to develop the type of nerve damage and circulatory problems that can lead to sciatica.

• Other conditions that can cause peripheral neuropathy. For example, alcohol abuse or uremia (a toxic syndrome resulting from kidney failure) can cause sciatica-like symptoms.

Patients with sciatica generally feel pain that begins in the lower spine and radiates down to the buttocks and into the back of the legs. Sciatica can affect one or both sides of the lower body. It often feels like a bad leg cramp, but pain may be experienced at any point along the nerve pathway. Sciatica is most likely to be felt in the following patterns:

• Lower back to the knee
  
  
• Middle of the buttock to the outside of the calf, top of the foot and into the space between the last two toes
  
  
• Inside the calf to the inner ankle and sole of the foot

Some patients with sciatica experience only a mild ache, whereas others feel an excruciating sharp, burning sensation. It is not unusual for the pain to begin mildly and to get progressively worse over time. In severe cases, the pain can feel like an electric shock. Pain is most likely to affect just one lower extremity and to worsen when sitting, coughing or sneezing.

Other symptoms that may accompany sciatica include:

• Numbness or muscle weakness along the nerve pathway in the leg or foot. Some patients will experience pain along part of the sciatic nerve and numbness along another part.
  
  
• Tingling. This feeling, sometimes described as a “pins-and-needles” sensation, occurs most often in the toes or part of the foot.
  
  
• Weakness of the knee or foot. Patients may have an inability to move the foot or bend the knee, or may experience difficulty walking. Rarely patients can have footdrop with advanced damage of the nerve.
  
  
• Loss of bladder or bowel control (incontinence). This symptom may indicate the presence of cauda equina syndrome, a rare disorder that affects the bundle of nerve roots (cauda equina) at the lower (lumbar) end of the spinal cord. These nerve roots send messages to and receive messages from the pelvic organs and lower limbs. Cauda equina syndrome sometimes is accompanied by numbness or tingling in the groin or genital area. It is an extremely serious condition that requires emergency medical care.

Sciatica symptoms that fail to resolve within six weeks or that worsen require medical attention. Patients should seek medical attention if they experience sudden, severe pain, numbness or muscle weakness in the back or leg. Other symptoms that may require a visit to a physician include pain that follows a traumatic injury or trouble controlling the bowels or bladder.

In diagnosing sciatica, a physician will review the patient's medical history and perform a physical examination. Special attention will be paid to the spine and legs, with testing to check muscle strength and reflexes. Tests that are likely to reveal the presence of sciatica include walking on toes or heels, rising from a squatting position (to test the strength) and lying on one's back and raising the legs one at a time straight up into the air (called the straight leg raise test).

The patient may be asked to complete a pain assessment form. Imaging tests may be performed to help identify the cause of sciatic nerve compression or to help rule out other potential causes of symptoms. These tests can include:

• MRI (magnetic resonance imaging). Probably the best test for diagnosing sciatica, this test uses powerful magnets and radio waves to produce cross-sectional images of the back. MRI can reveal damage to intervertebral discs and ligaments and the presence of tumors.

• CAT scan (computed axial tomography). This test produces detailed, cross-sectional images of the body. A contrast medium is sometimes injected into the spinal canal before x-rays are taken to help highlight problem areas. CAT scans can reveal herniated discs and tumors, but they also present risks such as infection and damage to the spinal cord.
  
  
• Spinal x-ray. This test may reveal the presence of narrowed discs (stenosis) or spondylolisthesis.

Tests that can detect damage to the sciatic nerves include:

• Nerve conduction studies. Use electrodes placed on the legs to record the electrical signals of a nerve.
  
  
• Electromyography. A test using needles inserted into leg muscles to measure electrical activity sent from the central nervous system (brain or spinal cord).

Even after all these tests, it may sometimes be difficult to diagnose what is causing sciatica.

In most cases, sciatica flare-ups are minor events that can be relieved without seeking medical attention. During a flare-up, patients should try to avoid activities that trigger sciatica pain. Rest can be helpful, but too much inactivity may worsen symptoms.

Other measures that may help reduce symptoms include:

• Cold packs (cryotherapy). Ice can be applied to painful areas for 15 to 20 minutes several times daily. Patients are advised to wrap ice in a towel or use a cold pack – ice should not be applied directly to the skin. At least 15 minutes should separate sessions of therapy with ice.
  
  
• Heat treatment (thermotherapy). Forty-eight hours after cold packs are first applied, patients can apply heat to areas that are causing pain. Methods of thermotherapy include warm packs, heat lamps or heating pads kept on the lowest setting. Patients who continue to experience pain are advised to alternate cold and warm therapy.
  
  
• Stretching. Passive stretching can help relieve compression. It is important not to jerk, bounce or twist during stretching.
  
  
• Over-the-counter pain medications. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen or naproxen can help relieve inflammation and pain. Analgesic medications such as acetaminophen relieve pain but do not reduce inflammation.
  
  
• Regular exercise. An active lifestyle is one of the best ways to combat chronic discomfort. During exercise, the body releases chemicals called endorphins that prevent pain signals from reaching the brain. These chemicals also help relieve depression and anxiety. People who add strength training and stretching to their exercise regimen can help slow age-related degenerative changes to the back. Patients should consult a physician before beginning an exercise regimen.

In some cases, sciatica may become severe enough to warrant medical attention. In such situations, treatments recommended by physicians may include:

• Prescription drugs. Prescription anti-inflammatories can provide relief at dosage levels that are higher than those found in over-the-counter medication. In addition, other medications that may help relieve pain brought on by sciatica include:
  
• • Anticonvulsants. Drugs primarily used to treat seizures. They also may be effective in treating certain types of nerve pain. Anticonvulsants are often prescribed with analgesics.
    
    
  • Antidepressants. Some antidepressants, particularly tricyclic antidepressants, can relieve pain and assist with sleep.
    
    
• Rehabilitation. Patients with a herniated disc may be advised to work with a physical therapist on a rehabilitation program that can help prevent recurrence of injury. Physical therapy can help patients correct their posture, strengthen the muscles of their backs and improve flexibility. In addition, a physician may prescribe occupational therapy so the patient can learn how to safely perform daily activities such as bathing and cooking, sometimes with the use of assistive devices such as shower benches.

• Acupuncture or acupressure.
  
  
• Injection therapy, such as:
  
• • Epidural corticosteroid injections. When other treatments fail, a physician may suggest treating sciatica pain with an injection of corticosteroid medication, which mimics the effects of the natural hormones cortisone and hydrocortisone in suppressing inflammation. However, these drugs must be used in limited doses under a physician's close supervision, as they can have substantial side effects.
    
    
  • Nerve blocks. Sciatic nerve roots can be injected with corticosteroids. These injections also work by decreasing inflammation around the nerve causing pain relief.
    
    Injection therapy should be performed by a trained pain management physician.
    
    
• Surgery. Spine surgery may be an option for patients who fail to respond to other treatments, or who have significant weakness or pain that keeps worsening. In most cases, surgery consists of removing part of a herniated disc (discectomy) that is pressing on a nerve and causing sciatic pain. A laminectomy may be another option. In many cases, surgery will provide short–term relief but cannot prevent degenerative changes that may cause pain to return over time.
  
  
• Spinal cord stimulation. This is a relatively new technology for sciatica patients who have failed conservative measures including nerve blocks and sometimes have also failed surgery.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about sciatica:

1. Could my leg pain, tingling, numbness and other symptoms be due to sciatica?
   
   
2. What else could be causing my symptoms?
   
   
3. What tests for sciatica might I undergo, and what do they involve?
   
   
4. What do my test results show?
   
   
5. What caused my sciatica?
   
   
6. My sciatica symptoms are mild. Are they likely to stay that way, or to get progressively worse?
   
   
7. If my sciatica affects only one leg, what are the chances it will affect the other side of my body as well?
   
   
8. Can I treat my sciatica at home? What methods should I use?
   
   
9. My home treatments for sciatica are not helping. What are my other treatment options?
   
   
10. Can I be referred to a pain management specialist?
    
    
11. Are there ways I can prevent sciatica?