WHAT ARE THE CAUSES OF SCIATICA?

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The sciatic nerve can be irritated by a number of conditions. The most common are:

• Inflamed piriformis muscle

• Herniated lumbar disc

• Lumbosacral muscle strain

• Spinal stenosis

• Ruptured disc

• Emotional stress

Less common causes to consider are: arthritis; endometrial cysts; ankylosing spondylitis; a sacroiliac ligament tear; and weak abdominal and back muscles. These terms may sound overwhelming, but each one is clearly defined within this post.

What is Piriformis Syndrome?

The piriformis muscles, which are in the buttock region just above the sciatic nerve, are responsible for rotating the hip outward when standing and for rotating the hip inward when sitting. These muscles can become inflamed from overwork or injury. The inflamed piriformis muscle, in one or both buttocks, can press against the sciatic nerve and therefore cause painful sciatica.

Prime candidates for piriformis syndrome include individuals who sit for extended periods of time, such as car drivers and office workers (especially those who keep their thick wallets in their back pockets), and individuals who stand for long periods of time, playing golf, shovelling snow, etc. Also, people who suffer from accidents that involve falling onto the buttocks, too much aerobic exercise, and simple leg-length discrepancies are at heightened risk for piriformis syndrome.
The primary symptom of piriformis syndrome is tenderness and sudden pain in the buttock region, aggravated by sitting and especially after first getting up in the morning. The discomfort can also follow along the pathway of the sciatic nerve.

A tingling, numbing sensation can develop in the buttock and leg region when sitting. The appropriate evaluation for piriformis syndrome would include: a history of injury; the location of pain; assessment of muscle strengths and weaknesses; testing of reflexes; and a musculoskeletal examination.

According to some researchers, it has been observed that in some people, the sciatic nerve actually passes through the belly of the piriformis muscle. Anyone with this anatomical condition is more susceptible to developing the symptoms of sciatica. This is due to the fact that the sciatic nerve is more likely to be compressed when the piriformis muscles experience any irritation.

Lumbar Herniated Disc

Lumbar discs are thick cushions of cartilage that separate the vertebrae in the lumbar region of the spine. Each disc has a hard, fibrous outer edge and a soft, gelatine-like substance in the center. They allow greater movement and flexibility between the vertebra and act like shock absorbers, distributing the body’s weight when the spine bends. The lumbar discs have no blood supply of their own. Therefore, they absorb nourishment from the surrounding tissue like a sponge.
During cycles of physical activity and rest, the discs squeeze the fluids back to the surrounding tissue and soak up fresh fluids. Over a long process of wearing down, various factors—such as repetitive lifting, poor posture, or loss of flexibility can inhibit nourishment absorption and cause a disc to become thin and brittle. This leads to a herniated disc.

A herniated disc occurs when some portion of the disc protrudes through the defected, worn down area. It is a displacement from proper alignment. A symptom of a herniated lumbar disc is a sudden, sharp, electric pain that radiates to the buttock and down the pathway of the sciatic nerve.

Secondary symptoms include: stiffness in the lower back; limitation in the flexion and extension of the back; weakened reflexes; numbness; tingling; hot and cold sensations; and hypersensitivity. Coughing and sneezing may aggravate a herniated disc. Standing or lying on the unaffected side and flexing the knees can alleviate it.

Several types of physical assessment may be used to determine a herniated lumber disc. The location of pain, a reflex evaluation, a muscle weakness test, and a sensory loss evaluation of the leg can help diagnose the problem. So, too, can the determination of flexibility in the spine, as well as the performance of a straight-leg-raising test. When a person with a herniated disc has his or her leg raised and straightened, pain will be felt in the leg, not in the back.

Lumbosacral Muscle Strain

When unnecessary tension is placed upon the supporting muscles of the back, strain is placed on the low back—that is, the lumbosacral region. A sedentary lifestyle, obesity, poor posture, and lack of exercise are all contributing factors to lumbosacral problems. A lumbosacral strain usually occurs from lifting objects improperly, from twisting without stretching, or from trauma to the lower back.
Symptoms of lumbosacral muscle strain generally include: the onset of pain after physical activity involving the low back; a dull, aching, persistent pain; and stiffness in the lumbosacral region. When tight muscles in this region press against and irritate the sciatic nerve, a burning, stabbing pain accompanied by some numbness and weakness may occur along the sciatic pathway. The pain radiates across the low back and occasionally into the buttock region. Movement of any kind, particularly standing, lifting, bending, and / or twisting, can aggravate this condition. Sitting and resting may temporarily alleviate it.

Although the strain can go away by itself, if the pain is persistent, a person may decide to seek diagnostic testing. A test to determine lumbosacral muscle strain is the straight-leg-raising test. If there is lumbosacral muscle strain, any pain elicited from this test will be felt in the low back and not in the leg.

What is Spinal Stenosis?

Spinal stenosis is a narrowing of the spinal canal. It is generally seen in the senior population. The narrowing is a result of the formation of bone spurs on the spine. This condition can cause the sciatic nerve to be compressed as it passes through the narrowed canal. There is a gradual onset of pain in the lumber region. The pain may radiate into the buttocks and occasionally down the legs.
The pain of spinal stenosis is brought on with exercise, prolonged standing, walking, or climbing stairs. People who suffer from this condition tire easily and need to rest after travelling short distances because of the back pain. Sometimes the discomfort can be relieved through rest or sitting. A full medical history and physical exam are generally needed to diagnose spinal stenosis.

Ruptured Disc

As explained previously, intervertebral discs are thick cushions of cartilage that separate and support the vertebrae. Often, poor posture will change the alignment of the spine, as it puts continuous strain on the vertebrae and discs. Continued strain over a long period of time can cause a disc to wear down and to protrude through the area of deterioration , the outer portion to split, and the disc to rupture that is, the soft, inner layer of the disc leaks out. A sudden, violent injury may also cause a disc to rupture.

An evaluation to determine the presence of a ruptured disc may include: a full medical history; determination of the precise location of pain and the type of pain; a reflex assessment; and tests for muscle weakness and sensory loss, particularly in the leg region experiencing sciatic symptoms.

A person with a ruptured disc will experience limitations in performing the straight-leg-raising test due to pain and / or lack of flexibility. Coughing, sneezing, and / or straining can aggravate a ruptured disc.
Emotional Stress
Emotional stress can be either a direct cause or a contributing factor to low back pain. Stress often occurs when the continuous demands of life overwhelm our ability to cope with them. These demands stressors can be internal, involving emotions and attitudes.

They can also be external, involving events in our lives that we cannot control, such as traffic and work deadlines. The body reacts to stressors by releasing stress hormones that increase heart rate and breathing rate, as well as tighten muscles throughout the body.

There are numerous causes of sciatica. With the right treatment the symptoms can be largely alleviated.