eMedicine Specialties > Neurosurgery > Spine

Spinal Stenosis

John Nk Hsiang, MD, PhD, Director of Spine Surgery, Seattle Neuroscience Institute

Updated: Jul 30, 2009

Introduction

Spinal stenosis refers to narrowing of the spinal canal, nerve root canals, or intervertebral foramina due to spondylosis and degenerative disk disease. This process usually occurs in the cervical and lumbar spine; it seldom occurs in the thoracic spine.

Frequency

Approximately 250,000-500,000 US residents have symptoms of spinal stenosis. This represents about 5 of every 1000 Americans older than 50 years. Current estimates indicate that 70 million Americans are older than 50 years. This number is estimated to grow by 18 million in the next decade alone, suggesting that the prevalence of spinal stenosis will increase.

Sagittal measurements taken of the anteroposterior diameter of the cervical spinal canal are highly variable in otherwise healthy persons. An adult male without spinal stenosis has a diameter of 16-17 mm in the upper and middle cervical levels. Magnetic resonance imaging (MRI) scans and reformatted computed tomography (CT) images are equally as effective in obtaining these measurements, while radiography is not accurate.

Etiology

Spinal stenosis is part of the aging process, and it is not possible to predict who will be affected. No clear correlation exists between the symptoms of stenosis and race, occupation, sex, or body type. The degenerative process can be managed, but it cannot be prevented by diet, exercise, or lifestyle.

The 2 forms of spinal stenosis are described as follows:

Primary stenosis is congenital and relatively uncommon. The condition is diagnosed more easily because patients are younger and usually lack other complicating medical problems such as diabetes or vascular insufficiency.
Acquired stenosis is a degenerative condition. Patients generally become symptomatic at age 50 years or older. Degenerative changes of the spine can include osteophyte formation, facet hypertrophy, bulging disks, and hypertrophy of the ligamentum flavum. Any of these processes can result in canal or foraminal narrowing. Degenerative spondylolisthesis can further compromise the canal.¹

Pathophysiology

The spine responds to physiological stresses with bone growth at the superior and inferior margins of the vertebral body (osteophytes). Osteophytes can form anteriorly or posteriorly. Posterior osteophytes narrow the intraspinal diameter and also cause lateral recess stenosis. This results in spinal cord or nerve root impingement. Furthermore, arthritic degeneration causes formation of synovial cysts and hypertrophy of the facet joints, which further compromise the patency of the spinal canal and the neural foramina.

During aging, the disks dehydrate and can compress and bulge. This process can cause tilting, slippage, or rotation of vertebral bodies. The ligamentum flavum also ossifies and becomes hypertrophic. The compressed disks result in shortening of the spinal column, which causes the ligamentum flavum to buckle inward and compress the spinal sac and nerve roots.²

Presentation

Usually, spinal stenosis occurs at the cervical and lumbar segments, resulting in 2 different clinical presentations.

Patients with cervical stenosis usually present with cervical radiculopathy, with or without myelopathy. Typically, the condition involves the lower cervical spine. Patients frequently complain of radiating arm pain with numbness and paresthesia in the involved dermatomes. Occasionally, associated weakness occurs in the muscles supplied by that nerve root. If the stenosis is severe enough, or if it is positioned centrally in the spine, patients may present with signs and symptoms of myelopathy (spinal cord dysfunction). Typically, these patients complain of finger numbness, clumsiness, and difficulty walking due to spasticity and loss of position sense. In more severe cases, the patients can have bowel and bladder control dysfunction. Upon examination, these patients have "long-tract signs" such as hyperreflexia and clonus.
Patients with lumbar stenosis usually present with a constellation of symptoms that include lower back pain, radiating leg pain (unilateral or bilateral), and possible bladder and bowel difficulties. The classic presentation is radiating leg pain associated with walking that is relieved by rest (neurogenic claudication). When patients bend forward, the pain diminishes. Rarely, patients with lumbar stenosis present with cauda equina syndrome (bilateral leg weakness, urinary retention due to atonic bladder).

Patients often endure spinal stenosis for years because they mistakenly accept their symptoms as an inevitable part of aging. Early treatment is important for a better outcome.

Indications

When a patient presents with signs and symptoms of myelopathy or cauda equina syndrome, urgent surgical decompression of the spinal cord or nerve roots is indicated. Significant muscle weakness due to nerve root impingement is also a strong indication for surgical intervention. If the patient has already developed muscle atrophy, a full return of muscle strength would not be expected even after surgical decompression.

Radicular pain is the most common symptom of spinal stenosis, and thus the most common indication for surgery. Pain is a totally subjective complaint, and no reliable, objective means measures pain severity. Therefore, it is up to the surgeon and the patient to decide if surgery is desirable. Usually, if the patient's quality of life is compromised because of pain and there are no effective or acceptable nonsurgical treatments, it is reasonable to recommend surgery.

Workup

Laboratory Studies

Laboratory studies do not help confirm a diagnosis of spinal stenosis, but they may be helpful in excluding other disease entities that cause similar symptoms. For example, a low sedimentation rate helps exclude diskitis (disk space infection); a normal result obtained from noninvasive lower limb vascular studies helps exclude vascular claudication.

Imaging Studies

The patient's history and physical examination are 2 of the most reliable means to establish the diagnosis, although it is not uncommon for patients to present with pain symptoms only and to have no abnormal findings upon physical examination. Therefore, imaging studies of the spine are absolutely necessary to establish the correct diagnosis.
Plain spine radiograph
- Although this is not the most sensitive imaging study to show stenosis from degenerative changes, it is useful in excluding fracture, spondylolysis, or neoplasm as the cause of symptoms.
- The flexion-extension views are very useful to show spinal instability.
MRI or CT myelogram
- These are the imaging studies of choice. MRI is the first choice because CT myelogram is invasive. However, if a better delineation of the bony anatomy and the specific nerve root's involvement is necessary, a CT myelogram has the advantage over MRI.
- CT scan alone is not as helpful, but it is a good alternative if MRI or CT myelogram is not possible.

For more information on imaging studies, please see the eMedicine Radiology article Spinal Stenosis.

Diagnostic Procedures

Other procedures that may aid in the diagnosis of spinal stenosis include spinal nerve root blocks, epidural steroids injection, electromyography, and somatosensory-evoked potentials. Unfortunately, only positive results are usually helpful in confirming a diagnosis. Negative results or responses do not exclude the diagnosis. A nerve root pain syndrome can be associated with a normal electromyography study finding.

Treatment

Medical Therapy

If symptoms are mild, nonsurgical treatment can be effective. Nonsurgical treatments include physical therapy, anti-inflammatory drugs, and epidural steroid injections. These treatments may be used to manage symptoms on a long-term basis for patients who are not surgical candidates. Urgent surgical intervention is indicated for patients who present with signs and symptoms of spinal cord compression.

Surgical Therapy

Surgical treatment for lumbar stenosis includes laminectomy and posterior foraminotomy at the involved levels. For cervical stenosis, either an anterior or a posterior approach can be used. Because most patients are elderly, they usually have comorbidities from cardiac or pulmonary problems. Multilevel decompression requires general anesthesia, and significant blood loss is possible. A cardiologist or pulmonologist must evaluate these patients before surgery. Many of these patients are taking antiplatelet medications. If possible, they should discontinue these drugs 1 week before the operation.

Lumbar laminectomy is straightforward. To obtain effective decompression of the lateral recess, the surgeon should remove the medial part of the hypertrophic facet joint. However, wide decompression and removal of much of the facet joints occasionally results in spondylolisthesis, particularly in patients who already demonstrate preoperative spinal instability. Sometimes, it is necessary to perform spinal fusion surgery after the decompressive laminectomy.

For cervical stenosis, surgical decompression can be performed through either the anterior or posterior approach. The posterior approach is indicated for multilevel compression or posterior compression from a hypertrophied ligamentum flavum. Again, violating the facet joints can result in development of swan-neck deformity. For this reason, some surgeons prefer a cervical laminoplasty to cervical laminectomy. Cervical laminoplasty allows decompression of the spinal cord and unilateral nerve roots with the preservation of the contralateral facet joints. It also allows for a construction of the elevated lamina to provide stability.

Frequently, cervical stenosis is caused by anterior compression due to osteophyte formation. An anterior approach is technically more demanding, carries a higher risk, and often requires fusion. In experienced hands, anterior decompression and fusion for 3 or fewer disk levels (2-level vertebral corpectomy) is relatively safe, and the success rate is high.

With more than 3 disk levels, the nonfusion rate and morbidity rate are significantly higher. For 1-level anterior cervical fusion, allograft is almost as effective as autograft in terms of fusion rate. Anterior cervical plating may not be necessary for single-level operations, even though US surgeons commonly perform it. For 2 or more levels of decompression and fusion, autograft is preferred over allograft.

Instrumentation using an anterior cervical plate is highly recommended in that setting. In general, surgery involving more than 2 levels of fusion is not indicated for patients in poor medical condition and with poor bone density.

After decompressive surgery, some patients, especially those with myelopathy, require physical therapy or rehabilitation.

Complications

Surgery for spinal decompressive laminectomy is a relatively safe procedure. The more common complications include wound infection, cerebrospinal fluid leak, and iatrogenic injury to neural structures. Long-term complications can include spinal instability.

As expected, the anterior approach to the cervical spine carries a greater risk of complications. Other than the usual risks of wound infection and nerve damage, additional risks include vascular injury (carotid and vertebral arteries), injury to the recurrent laryngeal nerve (with vocal cord paralysis), injury to the esophagus (and subsequent dysphagia), instrumentation failure, and failure of fusion.

The rate of nonunion is significantly higher in long-term smokers and with multilevels of fusion. The risk of complications increases with greater levels of decompression and in patients with other medical conditions, such as diabetes, and long-term steroid use.

Outcome and Prognosis

Early treatment is important for a successful outcome. Surgical decompression of the neural structures usually treats the symptoms effectively. Long-term pain relief is a common outcome, and most patients can resume active lives.

The surgeon must take great care to avoid a wide laminectomy. Removing less than 50% of the medial facet is usually a safe guideline, but this also depends on the patient's preoperative spine stability. Violation of the facet joints may cause the patient to develop spondylolisthesis in later years, which then requires spine fusion surgery.³

Future and Controversies

All adults older than 40 years have varying degrees of degenerative changes in their spinal columns. Although imaging studies of these adults show such changes, not every elderly person has symptoms of spinal stenosis. Therefore, selecting the correct patients for surgery is crucial and remains an issue of concern and study. Usually, the history, physical examination, and appropriate imaging studies provide enough information to make the correct diagnosis. However, some patients need additional studies, such as somatosensory evoked potentials, electromyography, and vascular tests, to confirm the diagnosis. The selection of decompressive procedures remains debatable (cervical laminectomy vs laminoplasty, anterior plating vs no plating).

Multimedia

Media file 1: Sagittal measurements taken of the anteroposterior diameter of the cervical spinal canal are highly variable in otherwise healthy persons. An adult male without spinal stenosis has a diameter of 16-17 mm in the upper and middle cervical levels. Magnetic resonance imaging (MRI) scans and reformatted computed tomography (CT) images are equally as effective in obtaining these measurements, while radiography is not accurate.

References

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Fehlings MG, Skaf G. A review of the pathophysiology of cervical spondylotic myelopathy with insights for potential novel mechanisms drawn from traumatic spinal cord injury. Spine. Dec 15 1998;23(24):2730-7. [Medline].
Trouillier H, Birkenmaier C, Kluzik J, et al. Operative treatment for degenerative lumbar spinal canal stenosis. Acta Orthop Belg. Aug 2004;70(4):337-43. [Medline].
[Guideline] Resnick DK, Choudhri TF, Dailey AT, Groff MW, Khoo L, Matz PG, et al. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 9: fusion in patients with stenosis and spondylolisthesis. J Neurosurg Spine. Jun 2005;2(6):679-85. [Medline].
[Guideline] Resnick DK, Choudhri TF, Dailey AT, Groff MW, Khoo L, Matz PG, et al. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 10: fusion following decompression in patients with stenosis without spondylolisthesis. J Neurosurg Spine. Jun 2005;2(6):686-91. [Medline].
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Keywords

spinal stenosis, lumbar stenosis, narrowing of the spinal canal, narrowing of the nerve root canals, narrowing of the intervertebral foramina, spondylosis, degenerative disk disease, cervical spine, lumbar spine, thoracic spine, primary stenosis, congenital stenosis, acquired stenosis, osteophytes, bone spurs, facet hypertrophy, bulging disks, hypertrophy of the ligamentum flavum, canal narrowing, foraminal narrowing, degenerative spondylolisthesis, cauda equina syndrome

Contributor Information and Disclosures

Author

John Nk Hsiang, MD, PhD, Director of Spine Surgery, Seattle Neuroscience Institute
John Nk Hsiang, MD, PhD is a member of the following medical societies: American Association of Neurological Surgeons, North American Spine Society, Sigma Xi, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.

Medical Editor

Paul L Penar, MD, Professor, Department of Surgery, Division of Neurosurgery, University of Vermont School of Medicine
Paul L Penar, MD is a member of the following medical societies: Alpha Omega Alpha, American Association of Neurological Surgeons, and Congress of Neurological Surgeons
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Allen R Wyler, MD, Former Medical Director, Northstar Neuroscience, Inc
Allen R Wyler, MD is a member of the following medical societies: American Academy of Neurological and Orthopaedic Surgeons, American Association of Neurological Surgeons, and Society of Neurological Surgeons
Disclosure: Nothing to disclose.

CME Editor

Paolo Zamboni, MD, Professor of Surgery, Chief of Day Surgery Unit, Chair of Vascular Diseases Center, University of Ferrara, Italy
Paolo Zamboni, MD is a member of the following medical societies: American Venous Forum and New York Academy of Sciences
Disclosure: Nothing to disclose.

Chief Editor

Further Reading

Clinical guidelines

North American Spine Society (NASS). Diagnosis and treatment of degenerative lumbar spinal stenosis. Burr Ridge (IL): North American Spine Society (NASS); 2007 Jan. 262 p.

Resnick DK, Choudhri TF, Dailey AT, Groff MW, Khoo L, Matz PG, Mummaneni P, Watters WC 3rd, Wang J, Walters BC, Hadley MN, American Association of Neurological Surgeons/Congress of Neurological Surgeons. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 9: fusion in patients with stenosis and spondylolisthesis. J Neurosurg Spine 2005 Jun;2(6):679-85.⁴

Resnick DK, Choudhri TF, Dailey AT, Groff MW, Khoo L, Matz PG, Mummaneni P, Watters WC 3rd, Wang J, Walters BC, Hadley MN, American Association of Neurological Surgeons/Congress of Neurological Surgeons. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 10: fusion following decompression in patients with stenosis without spondylolisthesis. J Neurosurg Spine 2005 Jun;2(6):686-91.⁵

Boswell MV, Trescot AM, Datta S, Schultz DM, Hansen HC, Abdi S, Sehgal N, Shah RV, Singh V, Benyamin RM, Patel VB, Buenaventura RM, Colson JD, Cordner HJ, Epter RS, Jasper JF, Dunbar EE, Atluri SL, Bowman RC, Deer TR, Swicegood JR, Staats PS, Smith HS, Burton AW, Kloth DS, Giordano J, Manchikanti L. Interventional techniques: evidence-based practice guidelines in the management of chronic spinal pain. Pain Physician 2007 Jan;10(1):7-111.⁶