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Nerve
root disorders result in segmental radicular deficits (eg, pain
or paresthesias in a dermatomal distribution, weakness of muscles innervated
by the root). Diagnosis may require neuroimaging, electrodiagnostic
studies, and systemic testing for underlying disorders. Treatment
depends on the cause but includes symptomatic relief with NSAIDs
and other analgesics.
Nerve root disorders (radiculopathies) are precipitated by chronic pressure on a root in or adjacent to the spinal column. The most common cause is a herniated intervertebral disk. Bone changes due to RA or osteoarthritis, especially in the cervical and lumbar areas, may also compress isolated nerve roots. Less commonly, carcinomatous meningitis causes patchy multiple root dysfunction. Rarely, mass spinal lesions (eg, epidural abscesses and tumors, spinal meningiomas, neurofibromas) may manifest with radicular symptoms instead of the usual spinal cord dysfunction (see Spinal Cord Disorders: Pathophysiology, Symptoms, and Signs). Diabetes can cause a painful thoracic or extremity radiculopathy by causing ischemia of the nerve root. Infectious disorders, such as those due to fungi (eg, histoplasmosis) and spirochetes (eg, Lyme disease, syphilis), sometimes affect nerve roots. Herpes zoster infection usually causes a painful radiculopathy with dermatomal sensory loss and characteristic rash, but it may cause a motor radiculopathy with myotomic weakness and reflex loss. Cytomegalovirus-induced polyradiculitis is a complication of AIDS.
Symptoms and Signs
Radiculopathies tend to cause characteristic radicular syndromes of pain and segmental neurologic deficits based on the cord level of the affected root (see Table 5: Peripheral Nervous System and Motor Unit Disorders: Symptoms of Common Radiculopathies by Cord Level ). Muscles innervated by the affected motor root become weak and atrophy; they also may be flaccid with fasciculations. Sensory root involvement causes sensory impairment in a dermatomal distribution. Corresponding segmental deep tendon reflexes may be diminished or absent. Electric shock–like pains may radiate along the affected nerve root's distribution.
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Table 5
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Symptoms of
Common Radiculopathies
by Cord Level
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Level
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Symptoms
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C6
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Pain in the trapezius ridge and tip of the shoulder, often radiating to the thumb, with paresthesias and sensory impairment in the same areas
Weakness of biceps
Decreased biceps brachii and brachioradialis reflexes
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C7
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Pain in the shoulder blade and axilla, radiating to the middle finger
Weakness of triceps
Decreased triceps brachii reflex
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T (any)
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Bandlike dysesthesias around thorax
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L5
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Pain in the buttock, posterior lateral thigh, calf, and foot
Footdrop with weakness of the anterior tibial, posterior tibial, and peroneal muscles
Sensory loss over the shin and dorsal foot
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S1
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Pain along the posterior aspect of the leg and buttock
Weakness of the medial gastrocnemius muscle with impaired ankle plantar flexion
Loss of ankle jerk
Sensory loss over the lateral calf and foot
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Pain may be exacerbated by movements that transmit pressure to the nerve root through the subarachnoid space (eg, moving the spine, coughing, sneezing, doing the Valsalva maneuver). Lesions of the cauda equina, which affect multiple lumbar and sacral roots, cause radicular symptoms in both legs and may impair sphincter and sexual function.
Findings indicating spinal cord compression include a sensory level (an abrupt change in sensation below a horizontal line across the spine), flaccid paraparesis or quadriparesis, reflex abnormalities below the site of compression, early-onset hyporeflexia followed later by hyperreflexia, and sphincter dysfunction.
Diagnosis
Radicular symptoms require MRI or CT of the affected area. Myelography is sometimes used if multiple levels are affected. The area imaged depends on symptoms and signs; if the level is unclear, electrodiagnostic studies should be done to localize the affected root, but electrodiagnostic studies cannot identify the cause.
If imaging does not detect an anatomic abnormality, CSF analysis is done to check for infectious or inflammatory causes, and fasting plasma glucose is measured to check for diabetes.
Treatment
Specific causes are treated. Acute pain requires appropriate analgesics (eg, acetaminophen , NSAIDs, sometimes opioids). NSAIDs are particularly useful for disorders that involve inflammation. Muscle relaxants, sedatives, and topical treatments rarely provide additional benefit. Chronic pain can be difficult to manage (see Pain: Treatment); acetaminophen and NSAIDs are often only partly effective, and chronic use of NSAIDs has substantial risks. Opioids have a high risk of addiction. Tricyclic antidepressants and anticonvulsants may be effective, as may physical therapy and consultation with a mental health practitioner. For a few patients, alternative medical treatments (eg, transdermal electrical nerve stimulation, spinal manipulation, acupuncture, medicinal herbs) may be tried if all other treatments are ineffective.
Herniated
Nucleus Pulposus
(Herniated, Ruptured, or Prolapsed Intervertebral Disk)
Herniated
nucleus pulposus is prolapse of an intervertebral disk through a
tear in the surrounding annulus fibrosus. The tear causes pain;
when the disk impinges on an adjacent nerve root, a segmental radiculopathy
with paresthesias and weakness in the distribution of the affected
root results. Diagnosis is by CT, MRI, or CT myelography. Treatment
of mild cases is with analgesics as needed. Bed rest is rarely indicated.
Patients with progressive or severe neurologic deficits, intractable
pain, or sphincter dysfunction may require immediate or elective surgery
(eg, diskectomy, laminectomy).
Spinal vertebrae are separated by cartilaginous disks consisting of an outer annulus fibrosus and an inner nucleus pulposus. When degenerative changes (with or without trauma) result in protrusion or rupture of the nucleus through the annulus fibrosus in the lumbosacral or cervical area, the nucleus is displaced posterolaterally or posteriorly into the extradural space. Radiculopathy occurs when the herniated nucleus compresses or irritates the nerve root. Posterior protrusion may compress the cord or cauda equina, especially in a congenitally narrow spinal canal (spinal stenosis). In the lumbar area, > 80% of disk ruptures affect L5 or S1 nerve roots; in the cervical area, C6 and C7 are most commonly affected. Herniated disks are common.
Symptoms and Signs
Herniated disks often cause no symptoms, or they may cause symptoms and signs in the distribution of affected nerve roots. Pain usually develops suddenly, and back pain is typically relieved by bed rest. In contrast, nerve root pain caused by an epidural tumor or abscess begins more insidiously, and back pain is worsened by bed rest.
In patients with lumbosacral herniation, straight-leg raises stretch the lower lumbar roots and exacerbate back or leg pain (bilateral if disk herniation is central); straightening the knee while sitting also causes pain.
Cervical herniation causes pain during neck flexion or tilting. Cervical cord compression, if chronic, manifests with spastic paresis of the lower limbs and, if acute, causes quadriparesis.
Cauda equina compression often results in urine retention or incontinence due to loss of sphincter function.
Diagnosis
CT, MRI, or CT myelography can identify the cause and precise level of the lesion. Electrodiagnostic studies may help identify the involved root. Because asymptomatic herniated disk is common, the clinician must carefully correlate symptoms with MRI abnormalities before invasive procedures are considered.
Treatment
Because a herniated disk desiccates over time, symptoms tend to abate regardless of treatment. Up to 95% of patients recover without surgery within 3 mo. Treatment should be conservative, unless neurologic deficits are progressive or severe. Heavy or vigorous physical activity is restricted, but ambulation and light activity (eg, lifting objects < 2.5 to 5 kg [≈5 to 10 lb] using correct techniques) are permitted as tolerated; prolonged bed rest (including traction) is contraindicated. Acetaminophen , NSAIDs, or other analgesics should be used as needed to relieve pain. Physical therapy and home exercises can improve posture and strengthen back muscles and thus reduce spinal movements that further irritate or compress the nerve root.
If lumbar radiculopathies result in persistent or worsening neurologic deficits, particularly objective deficits (weakness, reflex deficits), or in severe, intractable nerve root pain or sensory deficits, invasive procedures should be considered. Microscopic diskectomy and laminectomy with surgical removal of herniated material are usually the procedures of choice. Percutaneous approaches to remove bulging disk material are being evaluated. Dissolving herniated disk material with local injections of the enzyme chymopapain is not recommended. Lesions acutely compressing the spinal cord or cauda equina (eg, causing urine retention or incontinence) require immediate surgical evaluation (see Spinal Cord Disorders: Diagnosis and Treatment).
If cervical radiculopathies result in signs of spinal cord compression, surgical decompression is needed immediately; otherwise, it is done electively when nonsurgical treatments are ineffective.
Last full review/revision February 2008 by Michael Rubin, MD
Content last modified February 2008
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