Sciatica

by Leonid Soubbotin

The following literature based review elaborates on the clinical syndrome of sciatica and examines its presentation along with its causes and potential treatment plans for this condition.

I. Description

Sciatica is a presence of pain and tenderness at some point of the sciatic nerve¹. The pain is present in the leg and often radiates below the knee and into the foot and toes. As such, it is important to point out that sciatica is a symptom and not a specific diagnosis of a pathology as many different factors could be the root cause of the present condition. It is just as important for us to understand that any back problem can lead to a referred pain and must be distinguished from the pain caused specifically by an inflammation or an impingement of the sciatic nerve.

The term sciatica is misused by many in the health care field as well as by the general public¹. It is common for researchers and clinicians alike to refer to any radiculopathy into one of the lower extremities that is caused by a disc herniation as sciatica. However, such problems may be the results of a compression of nerve roots from L1 to L3 which are not a part of the sciatic nerve. At the same time, patients may refer to any pain that arises from the lower back and radiates into the leg as sciatica, though majority of the time this is simply a referred pain and is caused by neither a disc herniation nor a nerve-root compression.

While it is a difficult task, we must be able to distinguish between a radicular pain - nerve root pain that Sciatica is characterized by and a referred pain, that is not related to the condition, as the clinical course and treatment of the two conditions are different.

II. Anatomy

Sciatic nerve is comprised of the nerve roots of L4, L5, S1, S2 and S3. As it exits the pelvis through the greater sciatic notch it branches as it travels down the leg supplying the muscles of the posterior aspect of the thigh as well as the whole leg below the knee and the foot². Impingement or an inflammation at any of the above stated levels can causing a painful sensation at the effected spot as well as down the lower extremity, however compression or an inflammation at the nerve root can cause radicular pain down the leg and into the toes.

Pathophysiology

For a long time the main cause of sciatica was believed to be purely mechanical - a nerve-root compression by disc herniation. However several observations contradict this hypothesis^1,3:

- Presence of disc herniation in asymptomatic subjects
- Pressure on normal nerve roots does not cause pain
- Pressure on adjacent level nerve roots does not cause pain
- Severe symptoms without evidence of nerve root compression
- Symptom severity does not correlate with the size of the disc herniation
- Outcome might be favorable with conservative treatment
- Outcome might be favorable despite persistence of the disc herniation
- Discectomy has only moderate long-term success

While the researchers do not entirely reject the role of mechanical compression as a potential cause of sciatica, in recent years inflammation of neural tissues in lumbar disc herniation has been reported in much greater detail⁴. First, nucleus pulposus, the central soft component of the intervertebral disc and the bulging component in the disc herniation, has inflammatory properties⁵. Studies reported displacement of nucleus pulposus on the nerve roots to cause pain, electrical impulse abnormalities and cellular changes⁶. Second, local auto-immune reaction is also believed to be a potential cause of the inflammatory process⁷. Lastly, the mechanical compression itself can lead to an inflammation when light compression force is applied to a nerve root over a prolonged period of time⁸.

While less likely, it is possible for sciatica to be also caused by spinal stenosis, degenerative disc disease and isthmic spondylolisthesis.

III. Indications

Indicators for sciatica⁹:
- Unilateral leg pain greater than low back pain
- Pain radiating to foot or toes
- Numbness and paraesthesia in the same distribution
- Straight leg raising test induces more leg pain
- Localized neurology - that is, limited to one nerve root

IV. Incidence/Prevalence

Personal Risk Factors⁹:
- Age of 45-64 years
- Increasing risk with height
- Obesity
- Smoking
- Mental Stress
- Sedentary Lifestyle

Occupational Factors⁹:
- Strenuous physical activity - frequent lifting, especially while bending over and twisting
- Driving, including vibration of whole body

V. Clinical Presentation, Course and Prognosis

Clinical course of acute sciatica is favorable with the majority of pain and disability that comes with it resolving upon 2 weeks after the onset of the symptoms. In the past clinical trials, in half of all of the patients improvement was noted within 10 days of the onset of symptoms and in 75% reporting improvement after 4 weeks¹⁰. Full recovery was noted in 80% of the patients within 8 weeks and 95% within 1 year¹¹.

VI. Potential Etiologies

Herniation of the disc, the most likely cause of sciatica, can be the result of the normal aging process or a traumatic injury.

VII. Diagnosis/Special Orthopedic Tests

Sciatica is diagnosed by history taking and physical examination. If the symptom of a radiating pain in one leg is present along with a positive neurological test a diagnosis of Sciatica is given. Straight-leg-raising test, also called a Lasegue's sign, diagnoses nerve-root tension and has been shown to be a reliable tool that is commonly used in diagnosing Sciatica¹².

Signs and Symptoms that distinguish sciatica from a non-specific low-back pain:

- Unilateral leg pain greater than low-back pain
- Pain radiating to foot or toes
- Numbness and paraesthesia in the same distribution
- Straight-leg-raising test induces more leg pain and localized neurology, which is limited to nerve root

Diagnostic imaging may be implemented if a pathology other than disc herniation, such as infection or a malignance, is suspected to be the cause of the symptoms. Also, for patients who experience no change in their condition following 6-8 weeks of conservative, non-surgical treatment, imaging is recommended in order to achieve a more definite diagnosis of a herniated disc with nerve root compression. Since disc herniation commonly occurs in people who do not have sciatica, the surgery is only considered if the imaging results are in accordance with clinical symptoms¹³.

VIII. Conservative Treatment

Conservative, non-surgical, treatment of sciatica during the first 6-8 weeks is suggested and combines a non-pharmacological and pharmacological modalities. If infection, tumor, osteoporotic fractures or other specific causes are present or suspected further evaluation is required and may include imaging and laboratory diagnostics tests. In the case of opioid-resistant pain, motor deficit or cauda equina syndrome an emergency surgery is considered.

Non-pharmacological Modalities.

Patient education about the causes of sciatica, lack of need for laboratory testing and diagnostic imaging, and favorable outcomes and likely recovery without the surgical intervention plays a key role in patient's satisfaction and improvement ¹⁴. Physical therapy that includes therapeutic exercises program, spine mobilization as well as provision of information, specially for patients with more severe symptoms, is beneficial¹⁵.

Exercises for Sciatica from a Herniated Disc:¹⁷

There is currently no research data supporting the use of acupuncture, spinal manipulation and corsets to be beneficial in treatment of sciatica¹⁸. General rest or bed rest are contraindicated as well, as such activities have not been shown to provide any long term relief and can further exacerbate acute low-back pain as without physical activity back muscles will atrophy and become less able to support the back¹⁹. Traction has shown mixed results and even found to be harmful in some cases and is thus also not readily prescribed²⁰.

Pharmacological Modalities.

World Health Organization suggests the use of level I and II analgesics for relief of pain associated with sciatica¹⁴. Strong opiods are prescribed for patients suffering with severe pain, though it is important that patients be advised on the risks associated with taking that medication. NSAID's can also be used for pain modulation for a short period of time. Muscle relaxant, though they won't help with radicular pain²¹, can be combined with NSAID's for patients whose sciatica is accompanied by a lower back pain. In cases of chronic sciatica, antidepressants, much like muscle relaxants, can ease the back pain without effecting the radicular pain²². Epidural corticosteroid injections may be used to provide substantial short-term pain relief for 3-6 weeks, though offering no positive change on disability, use of surgery or time to return to work. Transforaminal periradicular injections have been found to be an effective treatment in reduction in the need for surgery²³, though posing a potential for severe complications, such as spinal cord infarctions, thus limiting their use.

IX. Surgery & post-op treatment

Absolute indications for surgery:

- altered bladder function
- progressive muscle weakness
- opiod-resistant pain intensity.

These symptoms are not common and surgery is usually performed in order to provide a quicker pain relieve and an improvement of disability to patients who are other wise slow to progress. Most authors suggest considering surgical discectomy if the patient fails to respond to 6-8 weeks of conservative treatment and disc herniation is found to be the cause of sciatica¹². In general, 5-10% of patients with sciatica require surgery in order to alleviate their symptoms²⁴.

Studies done in the past comparing individuals with similar symptoms at baseline have found better outcomes for those patients who underwent the surgery in comparison with those getting the conservative treatment in the outcomes of pain relief and self reported progress at a 1 year mark, however the differences were much less noticeable after 4 years and non-existent after 10 years²⁵.

Surgical intervention will provide faster relief for patients with sciatica, though the results of surgery and conservative care are similar at 1 year mark and beyond.

X. Use of Modalities for Treatment of Sciatica

Transcutaneous electrical nerve stimulation, which is a treatment with a low-voltage electrical current, as well as percutaneous electrical nerve stimulation, where electrical stimulation is passed through the skin into the soft tissue using probes, have both shown to be effective in reducing radicular pain and improving physical activity and quality of sleep¹⁶.

The use of heat treatment has been reported to be as effective of a modality as active therapeutic exercises, traction, manipulation or other conservative treatments in reducing symptoms associated with sciatica¹⁸.

Alternating between ice and heat applications can be more effective for pain modulation in some of the patients²⁶.

XI. Additional Web Based Resources

Lumbar Discectomy
Sciatica Interactive Video
Sciatica Exercises for Sciatica Pain Relief
Information on Piriformis Syndrome
Sciatica Resources from the National Institute of Health

XII. References

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4. Saal JS, Franson RC, Dobrow R, et al. High levels of inflammatory phospholipase A2 activity in lumbar disc herniations. Spine. 1990;15:674-678
5. McCarron RF, Wimpee MW, Hudkins PG, et al. The inflammatory effect of nucleus pulposus. A possible element in the pathogenesis of low-back pain. Spine. 1987;12:760-764
6. Byrod G, Rydevik B, Nordborg C, et al. Early effects of nucleus pulposus application on spinal nerve root morphology and function. EuroSpine Journal. 1998;7:445-449
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