(See also Evaluation of Neck and Back Pain.)
Sciatica is typically caused by nerve root compression, usually due to intervertebral disk herniation, bony irregularities (eg, osteoarthritic osteophytes, spondylolisthesis), spinal stenosis, or, much less often, intraspinal tumor or abscess. Compression may occur within the spinal canal or intervertebral foramen. The nerves can also be compressed outside the vertebral column, in the pelvis or buttocks. L5-S1, L4-L5, and L3-L4 nerve roots are most often affected (see table Motor and Reflex Effects of Spinal Cord Dysfunction by Segmental Level).
In patients with sciatica, pain radiates along the course of the sciatic nerve (symptoms related to nerve roots L4, L5, and S1), most often down the buttocks and posterior aspect of the leg to below the knee. The pain is typically burning, lancinating, or stabbing. It may occur with or without low back pain. The Valsalva maneuver or coughing may worsen pain due to disk herniation. Patients may complain of numbness and sometimes weakness in the affected leg.
Nerve root compression can cause sensory, motor, or, the most objective finding, reflex deficits. L5-S1 disk herniation may affect the ankle jerk reflex; L3-L4 herniation may affect the knee jerk.
Straight leg raising may cause pain that radiates down the leg when the leg is slowly raised above 60° and sometimes less. This finding is sensitive for sciatica; pain radiating down the affected leg when the contralateral leg is lifted (crossed straight leg raising) is more specific for sciatica. The straight leg raise test can be done while patients are seated with the hip joint flexed at 90°; the lower leg is slowly raised until the knee is fully extended. If sciatica is present, the pain in the spine (and often the radicular symptoms) occurs as the leg is extended. The slump test can also be done, similarly to the straight leg raise test, but with the patient "slumping" (with the thoracic and lumbar spines flexed) and the neck flexed. The slump test is more sensitive, but less specific, for disk herniation than the straight leg raise test.
Sciatica is suspected based on the characteristic pain. If it is suspected, strength, reflexes, and sensation should be tested. If there are neurologic deficits or if symptoms persist for > 6 weeks, imaging and electrodiagnostic studies should be done. Structural abnormalities causing sciatica (including spinal stenosis) are most accurately diagnosed by MRI or CT.
Electrodiagnostic studies can confirm the presence and degree of nerve root compression and can exclude conditions that may mimic sciatica, such as peroneal nerve palsy, multiple mononeuropathy, or polyneuropathy. These studies may help determine whether the lesion involves single or multiple nerve levels and whether the clinical findings correlate with MRI abnormalities (especially valuable before surgery). However, abnormalities may not be evident on electrodiagnostic studies for up to a few weeks after symptoms begin.
Acute pain relief from sciatica can come from 24 to 48 hours of bed rest in a recumbent position with the head of the bed elevated about 30° (semi-Fowler position). Measures used to treat low back pain, including nonopioid analgesics (eg, NSAIDs, acetaminophen), can be tried for up to 6 weeks. Drugs that decrease neuropathic pain (see Drugs for Neuropathic Pain), such as gabapentin or other anticonvulsants or low-dose tricyclic antidepressants (no tricyclic is superior to another), may relieve symptoms. Oral gabapentin 100 to 300 mg at bedtime is used initially and should be titrated up slowly to avoid adverse effects that might inhibit patient recovery. As with all sedating drugs, care should be taken in older patients, patients at risk of falls, patients with arrhythmias, and those with chronic kidney disease.
Muscle spasm may be relieved with therapeutic heat or cold, and physical therapy may be useful. Whether corticosteroids should be used to treat acute radicular pain is controversial. Given epidurally, corticosteroids may accelerate pain relief, but they probably should not be used unless pain is severe or persistent. Some clinicians try oral corticosteroids, but firm evidence of efficacy is lacking.
Surgery is indicated only for cauda equina syndrome or for unequivocal disk herniation plus one of the following:
Classic diskectomy with limited laminotomy for intervertebral disk herniation is the standard procedure. If herniation is localized, microdiskectomy may be done; with it, the skin incision and laminotomy can be smaller. Chemonucleolysis, using intradiskal injection of chymopapain, is no longer used.
Predictors of poor surgical outcome include
Sciatica is typically caused by nerve root compression, usually due to intervertebral disk herniation, osteoarthritic osteophytes, spinal stenosis, or spondylolisthesis.
Classically, burning, lancinating, or stabbing pain radiates along the course of the sciatic nerve, most often down the buttocks and posterior aspect of the leg to below the knee.
Loss of sensation, weakness, and reflex deficits can occur.
Do MRI and electrodiagnostic studies if there are neurologic deficits or symptoms persist for > 6 weeks.
Conservative treatment is usually sufficient, but consider surgery for disk herniation with a progressive neurologic deficit, or persistent, intractable pain.