Lumbosacral Radiculopathy

Lumbosacral radiculopathy is typically caused by nerve root compression, usually due to intervertebral disc 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). Radiculopathies that descend down the back of the thigh and beyond the knee are consistent with sciatica (L4, L5, and S1 nerve roots form the sciatic nerve). Radiculopathies that travel to the front of the thigh are not sciatica and travel along the femoral nerve (L1, L2 and L3).

The term sciatica is often used imprecisely to describe any pain in the lower back that may or may not radiate down the back to the leg. Its use should be avoided because it can lead to diagnostic confusion.

In patients with lumbosacral radiculopathy, 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 disc 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 disc 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 to 60° and sometimes less. This finding is sensitive for lumbosacral radiculopathy; pain radiating down the affected leg when the contralateral leg is lifted (crossed straight leg raising) is more specific for lumbosacral radiculopathy. 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 radiculopathy 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 disc herniation than the straight leg raise test.

• Clinical evaluation

• Sometimes MRI, electrodiagnostic studies, or both

Lumbosacral radiculopathy 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 lumbosacral radiculopathy (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 lumbosacral radiculopathy, 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 at least 2 weeks after symptoms begin.

• Activity as tolerated, analgesics, and sometimes medications that relieve neuropathic pain

• Physical therapy

• Sometimes oral or epidural corticosteroids

• Surgery for severe cases

Medications for Neuropathic Pain

Muscle spasm may be relieved with therapeutic heat or cold, and physical therapy may be useful.

The use of corticosteroids to treat acute radicular pain is controversial. Given epidurally, corticosteroids may accelerate pain relief, but they should not be used unless pain is severe or persistent. Some evidence suggests that a course of oral corticosteroids may result in a slight short-term improvement in pain for some patients with radicular low back pain; however, oral corticosteroids are likely to be ineffective for patients with nonradicular low back pain (1

Surgery is indicated for cauda equina syndromeor for unequivocal disc herniation plus one of the following:

• Muscular weakness that is worsening or not resolving

• Other progressive neurologic deficits

• Intolerable, intractable pain that interferes with job or personal functions in an emotionally stable patient and that has not lessened after 6 weeks of conservative treatment

Classic diskectomy with limited laminotomy for intervertebral disc 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

• Prominent mental health factors

• Persistence of symptoms for >6 months

• Heavy manual labor

• Prominence of back pain (nonradicular)

• Possibility of secondary gain (ie, litigation and compensability)