Lumbar Spinal Stenosis
Figure 1: Spinal stenosis. Top:
Compressed nerves within a
stenotic spinal canal (arrow.)
Bottom : Normal size spinal
canal (arrow) (MRI)
Lumbar spinal stenosis is a narrowing of the spinal canal due to degenerative changes in the lumbar spine. The canal is reduced in size to the point that compression of the cauda equina or a spinal nerve occurs, with pain and other neurologic symptoms of weakness or numbness in the legs.The stenosis may span several spinal motion segments or only involve one motion segment. It can be caused by a variety of conditions, both congenital and acquired.Acquired spinal stenosis is most often the result of degenerative changes to the vertebrae themselves and to the spinal disc.Abnormal bone growth (osteophytes) occurs at the vertebral edges adjacent to the disc spaces, intruding on the spinal canal and spinal ligaments.Degenerative changes of the disc and facet joints can result in a vertebra slipping forward, known as spondylolisthesis, (see next section).All of these conditions can progress to spinal stenosis [Figure 1 ]. If a preexisting congenital spinal stenosis exists where the patientês spinal canal is already narrowed, the patient is more vulnerable to tissue changes over time or from later acquired disease, and symptoms can be enhanced.
The most frequent symptom of spinal stenosis is back pain, often a back -ache" with a gradual onset, as opposed to sudden.Unlike many people with painful herniated discs, patients do not tend to tilt to the side in response to pain or have spasmodic pain.There can be radiation of pain to the buttocks, posterior thighs, and of the calves.Spinal stenosis of the lumbar spine is often manifested by leg pain or limping that is provoked by standing and walking and is relieved by rest, sitting down, or leaning forward. This group of signs and symptoms may be referred to by your doctor as claudication.Symptoms often mimic those caused by herniated discs and include both sensory (numbness/tingling) and motor changes (weakness) in the leg.Any bowel or bladder changes should be discussed immediately with your doctor as they could represent progression towards development of the cauda equina syndrome (see below) and immediate surgical decompression may be necessary. Symptoms that suggest a diagnosis of spinal stenosis can point to other disorders (infection, vascular insufficiency, tumor) as well.
During physical and neurological examinations by your doctor, you may be asked to assume flexion and extension positions to reproduce your symptoms.In spinal stenosis, extension of the back is likely to produce symptoms suggestive of the disorder, for this posture narrows the spinal canal and accentuates the stenosis.Your doctor may ask you to walk back and forth and then repeat some aspects of the physical exam.This is because activity can enhance the symptoms of spinal stenosis.
A series of plain X-rays may be the initial imaging studies, but findings can only be suggestive of this condition.X-rays allow your doctor to rule out other causes of pain for your symptoms, check on how straight your spine is and the diameter of your spinal canal.Computed tomography (CT), CT-myelography, magnetic resonance imaging (MRI) are preferred imaging techniques to evaluate and diagnose the bony and soft tissue abnormalities of spinal stenosis.As opposed to the usual standing or lying positions, you may be asked to flex and extend your spine to enhance the images.
Although not routinely performed for the evaluation of spinal stenosis, various nerve function (electrophysiologic) tests may be performed to differentiate claudication symptoms attributable to spinal stenosis from symptoms secondary to other disorders (such as diabetic neuropathy).These tests include electromyography (EMG), somatosensory evoked potentials (SSEP) studies, and nerve conduction velocity studies.
Nonoperative care for spinal stenosis parallels that provided for herniated discs: bed rest, nonsteroidal or steroid medication and progressive ambulation, with pain medication as necessary.A rehabilitation and fitness program with stretching and strengthening exercises is also prescribed.Physical rehabilitation should refrain from extension exercises for these may worsen symptoms.Exercises involving flexion, pelvic stabilization, and lower extremity strength, as well as a host of modalities, such as transcutaneous electric nerve stimulation (TENS), ultrasongraphy, heat massage are commonly employed.
When nonoperative treatment fails or symptoms progress despite of treatment, surgical management is usually indicated. Adequate decompression of the identified pathology (cauda equina and nerve roots) should include laminectomy and partial facetectomy without destabilizing the spine.Spinal fusion is often performed in patients with surgical instability, spondylolisthesis, and degenerative scoliosis.