Sciatica

Sciatica presents with a range of symptoms which are often characteristic enough to make a diagnosis. Symptoms are mainly neurological and related to the musculoskeletal system.

Musculoskeletal symptoms

Symptoms begin with mild to moderate pain in the lower back and buttocks which radiates down the leg. There is numbness and a pins and needles sensation (paraesthesia) in the affected limb. Symptoms can be in just one limb or rarely, in both. The pain is sometimes so severe that the affected individual is in extreme discomfort and debilitated.

Neurological symptoms

Sciatica is always due to nerve involvement. The sciatic nerve may be directly involved as in the case of intervertebral disc herniation or protrusion or due to a tumor. Or the nerve may become indirectly involved due to a spasm or excessive contraction of the piriformis muscle, as in the piriformis syndrome [5]. It may also arise due to indirect nerve involvement in pregnancy.

Complications 

• Irreversible nerve damage leading to persistent pain
• Chronic sciatica
• Partial or complete loss of sensation in the involved limb
• Immobility
• Incompletely healing lower limb injuries

Risk factors

Some people are more at risk for developing sciatica. Common risk factors include:

• Extremely tall people
• Pregnant females
• Improper exercising
• Lower spinal lesions
• Tumors in the lumbar or sacral region
• Degenerative bone or muscle diseases
• Old age
• Athletes
• Sedentary lifestyle

Diagnosis is based on a complete history and physical examination.

A complete work up may include:

Checking for Lasegue's sign: In this test, the involved leg is passively flexed between 30 to 70 degrees and if the pain appears or aggravates, it is taken to be positive for sciatica.

Computerized Tomography Scan (CT): A CT scan be be conducted to check for possible causes of sciatica like spinal disc herniation or lumbar canal stenosis [7].

Magnetic Resonance Imaging (MRI): An MRI may be conducted for a more through scan for spinal lesions or tumors.

Treatment for sciatica is prolonged bed rest, physiotherapy and pain relieving medications [8], if needed. The pain subsides on its own if the underlying cause is detected and treated.

Sciatic pain occurs in response to obvious trauma, or due to internal wear and tear. It may arise due to jerky movements or posture change which may somehow irritate the sciatic nerve [6].
Whatever the cause may be, the pain is often sudden in onset and increases gradually but may subside after some time.

Sciatica, though not necessarily continuous for life, does have a tendency to reoccur, often without any warning or predisposing factor. The pain lasts around for a few days to a few weeks and then subsides. Proper bed rest, medication and physiotherapy may speed up the process of alleviating the pain.

Sciatica is caused by any disease or pressure or trauma that results in compression of the nerve roots from L4 to S3. The symptoms of sciatica can be presented with the following conditions [2]:

1. Spinal Disc Herniation: The intervertebral discs are composed of an inner soft portion called nucleus pulposus surrounded by an outer thicker and stronger ring called annulus fibrosus. The integrity of the outer fibrous ring keeps the central portion in place. If there is a tear, especially on the posterio-lateral aspect of the ring, the inner nucleus pulposus may herniate outwards. This herniation may put pressure on the nerve roots, or cause an inflammatory response which may damage the nerve roots. Either way, due to spinal disc herniation, sciatica may arise.
2. Spinal Disc Protrusion or Slip Disc: This condition is somewhat similar to the spinal disc herniation. The difference is that the annular ring, in this case, is intact. The nucleus pulposus does not squeeze out so there is no herniation. Instead, due to increased pressure on the lumbar and sacral vertebras, and thus the intervertebral discs, the disc itself slightly slips out. This causes a protrusion, commonly in the posterior aspect, called a disc slip. This protrusion of the intervertebral disc puts pressure on the surrounding nerve roots which then causes sciatica.
3. Degenerative Disc Disease: This condition is a result of either aging or due to trauma which causes unresolved inflammation in the lumbar area leading to damage to the intervertebral discs. As a result of the inflammatory process, or sometimes direct trauma, the weakened disc is prone to cause nerve damage, sometimes leading to sciatica.
4. Lumbar Spinal Stenosis: It is a condition in which factors like slipped disc, inflammation, tumors, bony spurs, etc cause the spinal canal to narrow down. This narrowing or stenosis of the lumbar spinal canal causes damage to the cauda equina and/or the nerve roots, leading to sciatica.
5. Piriformis Syndrome: In about 15% of people, the sciatic nerve travels through or underneath the piriformis muscle. So a contraction or spasm in the muscle may put excessive pressure on the nerve causing sciatic pain to arise.
6. Pregnancy: In some pregnancies, the weight of the fetus may cause pressure on the sciatic nerve leading to sciatica.
7. Other: Tumors may increase the pressure of the vertebral canal or directly impinge upon the sciatic nerve roots causing sciatica. Injury or trauma to the spine may also result in lifelong pain in the lower back, buttocks and legs.

None of the studies conducted have been specific for sciatica, but rather have been based on the diseases that may cause sciatica, such as lumbar disc herniation, etc. So the exact occurrence of sciatica is unknown.

Race: Sciatica has no known predilection to race or cast.

Ag: It is more common in older people due to age-related wear and tear of the spinal discs leading to herniation, and weakening of the vertebral canal leading to lumbar canal stenosis [1].

Sex: There are no definite studies declaring a predisposition in either sex, however, some studies suggest a higher prevalence in males.

As mentioned earlier, the sciatic nerve arises from 5 nerve roots, beginning from lumbar 4th to sacral 3rd. Sometimes, nerve fibres from L3 may also be involved. The lumbo-sacral plexus forms in the substance of the psoas muscle and the sciatic nerve, which arises when these nerve roots unite, passes beneath the piriformis muscle, through the greater sciatic foramen into the leg [3].

Damage to the nerve roots, due to any number of causes like those mentioned in the previous segment, leads to pain in the regions the nerve traverses. These regions include the lower back, buttocks, thighs, legs and feet.

Sometimes, the whole lower limb may be involved, sometimes just the proximal part or the distal portion of the limb, depending upon the nerve root involved. Sciatica does not necessarily arise on both lower limbs. It is often present in just one limb, unless there is a significant spinal injury involved [4].

By avoiding the common risk factors such as improper exercising, sudden, twisting movements that may damage the nerve and a sedentary life style, sciatica can be prevented.

Also taking a healthy diet, so as to prevent bone diseases and muscle weakening, may decrease the chances of developing sciatica [10].

Sciatica, or sciatic neuritis, is a common condition that affects the whole or part of the sciatic nerve. Damage or compression to any one of the nerve roots causes characteristic and often progressive symptoms to appear. 

The sciatic nerve is the largest and thickest nerve of the body. It is formed from L4 to S3 segments of the sacral plexus, which emerge out from the lower spinal cord and merge together in front of the piriformis muscle. The nerve then passes through the greater sciatic foramen and leaves the pelvis, entering the back of the leg. While moving downwards, the sciatic nerve divides into its two branches:

Common fibular nerve: Which courses in and supplies the anterior and lateral compartments of the leg. It also innervates the dorsum of the foot.

Tibial nerve: Which travels in the posterior compartment of the leg, supplying both the muscles and the skin. It also gives sensory innervation to the sole of the foot.

If any one of the five nerve roots is compressed, either when it emerges out of the cord or during the path where it unites with the others, it causes sciatica.

The symptoms include sudden, mild to severe pain in the lower back, moving downwards in the buttocks, back of the leg and sometimes as far as to the foot. The pain may or may not be accompanied with numbness and paraesthesia.

Definition

Sciatica is referred to pain in the lower back which radiates to the buttocks and one or both the legs. It is accompanied by numbness, tingling and a pins and needles sensation in the affected limb.

Cause

It is due to irritation, damage or compression of the sciatic nerve, which supplies the lower limb muscles and skin. It arises most commonly due to spinal disc herniation or protrusion (slipped disc).

Signs and Symptoms 

Numbness, tingling and pain in the lower limbs are the presenting symptoms. The pain may be localised to just the back, or involving the entire leg; from the hip to the foot. The severity of the pain is also varying. It may be mild to extremely severe that it immobilises the patient.

Treatment

It includes prolonged bed rest and physiotherapy. The underlying cause should be identified and treated [9].

Prevention

With the right lifestyle and diet, and avoidance of the risk factors may prevent the occurrence of sciatica.

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9. Breivik H, Hesla PE, Molnar I, et al. Treatment of chronic low back pain and sciatica. Comparison of caudal epidural injections of bupivacaine and methylprednisolone with bupivacaine followed by saline. In: Bonica JJ, Albe-Fessard D, eds. Advances in pain research and therapy. Vol 1. New York: Raven Press; 1976:927-32.
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