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 usually by MRI or CT. 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).
(See also Overview of Peripheral Nervous System Disorders.)
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.
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.
MRI or CT can identify the cause and precise level of the lesion. Rarely (ie, when MRI is contraindicated and CT is inconclusive), CT myelography is necessary. Electrodiagnostic testing may help identify the involved root.
Because an asymptomatic herniated disk is common, the clinician must carefully correlate symptoms with MRI abnormalities before invasive procedures are considered.
Because a herniated disk desiccates and shrinks over time, symptoms tend to abate regardless of treatment. Up to 85% of patients with back pain—regardless of cause—recover without surgery within 6 wk.
Treatment of a herniated disk 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. If symptoms are not relieved with nonopioid analgesics, corticosteroids can be given systemically or as an epidural injection; however, analgesia tends to be modest and temporary. Methylprednisolone may be given, tapered over a 6 days, starting with 24 mg po daily and decreased by 4 mg a day.
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.
Invasive procedures should be considered if
Microscopic diskectomy and laminectomy with surgical removal of herniated material are usually the procedures of choice. Percutaneous approaches to remove bulging disk material are still 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 Compression : Diagnosis).
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.
Herniated disks are common and usually affect nerve roots at C6, C7, L5, or S1.
If symptoms develop suddenly and back pain is relieved with rest, suspect a herniated disk rather than an epidural tumor or abscess.
Recommend analgesics, light activity as tolerated, and exercises to improve posture and strength; however, if pain or deficits are severe or worsening, consider invasive procedures.