Characterized by radiating pain in an area of the leg typically served by one nerve root in the lumbar or sacral spine.
Associated pain radiates from the buttock downward along the course of the sciatic nerve
Pain radiates from the low back along the sciatic nerve to the back of the thigh and down the leg, and is accompanied by clinical findings suggestive of compression or irritation of the lumbosacral nerve root.
Sometimes associated with sensory and motor deficits.
Most commonly caused by a herniated disk.
Generally is a self-limited process and resolves within three months in 70-90% of patients.
When symptoms do not improve, surgical discectomy is the excepted treatment.
Studies report that there is a modest benefit for surgical intervention that diminishes with time since the onset of symptoms.
Most studies however included patients with symptoms within three months of onset and with acute sciatica.
Prolonged symptom duration has an adverse effect on outcomes, with surgical and nonsurgical management.
It is suspected prolong pain may derive from chronic nerve compression leading to irreversible damage to the microvasculature supporting the spinal nerves, and other changes within the substance of the nerve roots, or changes in the central transmission of pain impulses.
In a study of patients with persistent pain for 4-12 months discectomy was superior to non-operative care for the primary outcome of leg pain intensity at six months after enrollment (Bailey CS).
Annual incidence estimated of 5 cases per 1000 adults annually.
Occurs in 4-6% of the U.S. population.
Prevalence in clinically verified sciatica ranges between 2.2 and 5.1% in the general population, between 2.7 and 5.7% in men, and between 1.4 and 4.5% in women.
Prevalence varies widely with the highest incidence 40%.
Most instances of sciatica occur in the fourth and fifth decades of life.
Onset may begin suddenly with physical activity or more slowly.
The pain radiates from the middle or lower buttock , and proceeds dorsolaterally in the thigh when compression of the L5 nerve root is involved and posteriorly in cases of compression of S1.
Sciatica pain associated with L4 compression is anterior lateral in the thigh and maybe misdiagnosed as hip disease.
When sciatic nerve-root pain extends below the knee, its location is related to the superficial sensory distribution of the affected spinal root.
Sciatica is usually unilateral due to the configuration of disk rupture and with foraminal stenosis from osteoarthritis of the spine, but bilateral pain may result in central disk herniation, lumbar stenosis, and spondylolisthesis.
The etiology is multifactorial and risk factors include: overweight and obesity, and smoking.
Current smoking increases the risk of sciatica by 35%, and hospitalization or surgery due to sciatica by 45%.
Smoking cessation reduces the excess risk of sciatica, and past smokers are 9-10% percent more likely to have sciatica than never smokers.
Overweight increases the risk of clinically verified sciatica by 12% and hospitalization for sciatica by 16%.
Obesity increases the risk of sciatica by 31% and hospitalization for sciatica by 38%.
Low back pain usually accompanies sciatic pain but is not always present.
Disk rupture in the L5-S1 area is usually associated with aching back pain and the pain increases as does the sciatic pain with coughing, sneezing, straining, or Valsalva maneuver.
Natural history results in resolution of leg pain within 8 weeks for majority of patients.
Principal source is compression of a lumbar root by disk material that has ruptured through the annulus.
85% of cases associated with a disk disorder.
It is a more persistent and disabling condition than other low back pain syndromes.
Modestly associated with obesity.
The sciatic nerve is the largest nerve in the body: the 4th and 5th lumbar nerves and the first 2 sacral nerve roots join in the lumbosacral plexus forming the peroneal and tibial nerves ensheathed as the sciatic nerve.
Abnormalities anywhere along the course of the sciatic nerve can give rise to sciatica symptoms.
Most commonly the area of involvement is at the site of the disk rupture and osteoarthritis at L4-L5 and L5-S1 and less frequently L3-L4.
In the above sites there is usually compression of the nerve root below the corresponding disk.
Sciatica mechanism may be related to distortion of the nerve root or its sensory ganglion or to the effect of local inflammatory cytokines.
Sciatic injury may occur at other sites including the lower pelvic cavity, buttock, gluteal fold, and proximal biceps femoris muscle.
Bilateral sciatic pain that is brought on by walking can simulate vascular claudication and is caused by compression of the cauda equina roots.
Compression of the cauda equina roots is called neurogenic claudication, the Verbiest syndrome.
Paresthesias in the dermatomal distribution of a nerve root may be present, but sensory symptoms and signs are not a prominent feature of sciatica.
Rarely associated with a downward tilted pelvis during walking in cases of gluteal weakness due to compression of S1.
Compression of S1 nerve root is usually associated with reduction or loss of the ankle reflex.
L3 for L4 compression associated with variable reduction in the knee reflex.
L5 compression has inconsistent reflex changes.
Weakness maybe present in less than half of patients with sciatica, but infrequently severe to cause foot drop with a L5 radiculopathy.
The strait-leg-raising test (Lasegue’s test) refers to having the patient in the supine position and raising the leg with the knee extended stretching the nerve root over the protruding disc resulting in nocifensive response of muscle contraction.
A positive straight-leg-raising test reproduces were markedly worsens pain and resistance to further elevation of the leg occurs.
With this test the diagnosis of disk compression is likely if pain radiates from the buttock to below the knee when the angle of the leg is between 30-70°.
Straight-leg-raising test sensitivity for disc herniation is approximately 90%, but specificity for the diagnosis is low.
Straight-leg-raising test maybe false in patients with hamstring and gluteal abnormalities.
Straight-leg-raising when accompanied by dorsiflexion of the foot or large toe increases the sensitivity of the test.
The crossed straight-leg-raising test known as the Fajersztajn’s test involves raising the unaffected leg.
In the crossed straight-leg-raising test a positive test indicates sciatic pain can be elicited in the opposite affected leg and this test is 90% specific for disk herniation on the contralateral side but is insensitive.
Radiographic imaging and electrophysiological evidence of nerve root compression testing corroborates disk or spine disease but are not necessary unless surgery is required.
Lumbar spine x-rays may show reduced height of intervertebral space, spondylolisthesis, osteomyelitis or tumor involvement of the vertebral body.
MRI can indicate site and nature of disk rupture, osteoarthritis, spondylolisthesis, foraminal stenosis, and joint facet abnormalities.
CT scans are performed less frequently but can reveal most herniations and structural changes of the spine.
Bulging disks and related minor deformities generally do not cause compression of the nerve roots and do not explain persisting sciatica.
Disk rupture is seen in fewer than 1% of asymptomatic patients.
Nerve conduction studies and electromyography can reveal the distribution of muscular denervation corresponding to a nerve root.
Denervation occurs days to weeks following injury and takes longer in distal than proximal muscles.
Findings include fibrillation and sharp waves in muscles that correspond to a single nerve root injury, combined with normal sensory potential from nerves that carry that root.
Testing of 4-5 realted muscle groups including those of the paraspinal areas is adequate for diagnosis.
Electromyography is not standard and most cases do not require testing.
The role of EMG has not been established in sciatica and some guidelines do not require testing.
Majority of cases are treated conservatively, and only a small percentage of cases eventually need surgery.
A relatively uncommon cause for hospitalization.
Surgical treatment offered only after a period of conservative management, but the optimal time to utilized surgery is not known.
Pyriformis syndrome can cause sciatica by compression of the sciatica nerve underlying the pyriformis muscle.
Pyriformis muscle stabilizes and serves as an external rotator of the hip.
Pyriformis syndrome associated with focal mid-buttock pain, tenderness over the sciatic notch, aggravation of pain on sittings and with increased pyriformis muscle tension such as external rotation of the hip.
While relief of symptoms is twice as fast among patients treated with early surgery as among those treated with conservative management, a randomized trial revealed that there was not a better overall 1-year functional recovery rate compared to a course of prolonged conservative therapy with an offer for subsequent surgery.
58% of patients with clinical symptoms for symptom-free within 30 days in 88% was symptom-free at six months (Hakelius A).
Most cases of acute radiculopathy improve within several months indicated that approximately two thirds of herniated lumbar discs undergo significant (greater than 50%) resorption within one year.
96% of patients with lumbosacral radiculopathy had good or excellent outcomes at a mean follow up of 31 months (Saul JA, Saul JS).
A controlled study of patients with ongoing lumbosacral radicular pain after three months of conservative management have improvement in pain with microdiscectomy compared to ongoing conservative care: patients may have improvement in pain at six and 12 months if surgery is performed, but outcomes are similar at two years.