Lumbar Spinal Stenosis

Article Author:
Lite Wu
Article Editor:
Ricardo Cruz
Updated:
9/27/2018 3:09:03 PM
PubMed Link:
Lumbar Spinal Stenosis

Introduction

Lumbar spinal stenosis is a common source of leg and back pain. It refers to a narrowing in the vertebra, in the areas of the central canal, lateral recess or the neural foramen.  When Lateral recess and neural foramen are stenosed, symptoms of lumbar radiculopathy may also be demonstrated [1]. Despite its prevalence, currently, there is no universally accepted definition of lumbar spinal stenosis, and there is also a lack of generally accepted radiologic diagnostic criteria[2]. Lumbar spinal stenosis is a significant cause of disability in the elderly, and it is the most significant cause of spinal surgery in patients over 65 years of age [3]. Therefore it is important for clinicians to recognize and treat lumbar spinal stenosis effectively.

Etiology

Degenerative spondylosis is a significant etiology of lumbar spinal stenosis. With aging, wear-and-tear changes and traumas, amongst other factors, the intervertebral discs can degenerate and protrude posteriorly, causing increased loading of the posterior elements of the vertebrae. This can lead to posterior vertebral osteophyte formation (uncinate spurs), facet hypertrophy, synovial facet cysts, and ligamentum flavum hypertrophy, which in turn will cause spinal stenosis.

Degenerative spondylolisthesis is another cause of lumbar spinal stenosis. When degenerative changes of the spine occur, the pars interarticularis can be fractured, and the resulting instability can lead to forward translation of the vertebra.  Sufficient anterior slippage of one vertebra on top of the next vertebral segment (most commonly L4-on-L5) can narrow the spinal canal, leading to stenosis.

Other acquired conditions, although rarer than the aforementioned conditions, should also be considered by the clinician. These include space-occupying lesions, post-surgical fibrosis, and rheumatologic conditions as well as other skeletal diseases such as ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis [4]

Even more rarely, lumbar spinal stenosis may be secondary to congenital causes such as achondroplasia, which can lead to short pedicles with medially placed facets.

Epidemiology

Because of a lack of universally accepted definition for lumbar spinal stenosis, the exact epidemiology is difficult to determine. In an ancillary Framingham study, where test subjects underwent CT scan to determine the central diameter of lumbar spinal canals, absolute lumbar spinal stenosis was defined as a diameter of less than 10mm.  The prevalence of acquired lumbar spinal stenosis was 19.4%, for population aged between 60–69 years.  In a  Japanese population-based study where subjects underwent a symptoms questionnaire to predict lumbar stenosis, it was found that incidence increased with age, with 1.7–2.2% between ages 40-49, and 10.3%–11.2% between ages 70 to 79[5]. It is also a significant contributor to spinal surgery in the US, 5.9 per 100 patients progressed to lumbar fusion within 1 year from the time of diagnosis of lumbar degeneration [6].

Pathophysiology

The causes of neurologic symptoms of lumbar spinal stenosis have been thought to originate from the compression and ischemia of nerve roots. Nerve root compression can originate from direct mechanical compression or increased intrathecal pressure due to the narrowing of the canal. Inflammation of nerve roots is also a plausible but less likely mechanism of neurologic symptoms in lumbar spinal stenosis [7]

History and Physical

Classically, lumbar spinal stenosis presents as pain exacerbated by prolonged ambulation, standing, and with lumbar extension, and is relieved by forward flexion and rest. Neurogenic claudication is an important feature of lumbar spinal stenosis. Symptoms are typically bilateral, but usually asymmetric. Low back pain, numbness, and tingling are present in a majority of patients. Numbness and tingling in lumbar spinal stenosis involve usually the entire leg, and rarely involves only a single nerve root distribution.[8] Approximately 43 percent of the patients experience weakness. Patients may also report walking upstairs being easier than walking downstairs, as the back is forward flexed with stairs climbing. If patients present with new-onset bowel or bladder dysfunction, saddle anesthesia, bilateral lower extremity weakness and/ or increased lower extremity, the patient may have developed cauda equina or conus medullaris syndromes. 

A thorough physical examination should be performed on patients with suspected lumbar spinal stenosis. Pain with passive and active lumbar extension can be elicited. Although it is possible that patients can have superimposed lumbar radiculopathy, it should be noted that neurologic examinations on patients with lumbar spinal stenosis are typically normal, and only 10 percent of patients would present with a positive straight leg raise test. [9] Pedal pulses should also be checked during physical exam as vascular claudication can present similarly. 

Evaluation

As mentioned previously, there is no consensus on the definition of lumbar spinal stenosis diagnostic criteria. However, in evaluating low back pain, neuroimaging is indicated when there is new-onset symptoms and suspicion of lumbosacral radiculopathy or spinal stenosis. In patients without suspicion of infection, metastasis or postoperative spine symptoms, non-contrast MRI of the lumbosacral spine is the modality of choice for lumbar spinal stenosis, and CT myelography can be utilized when MRI is contraindicated [10]. Many authors use an intraspinal canal area of less than 76MM² and 100mm² for severe and moderate stenosis, respectively. Anteroposterior spinal canal diameters of less than 10mm are also frequently used for the diagnosis of lumbar spinal stenosis. One must note that lumbar spinal stenosis is a common incidental radiological finding especially in patients over 60 years old, and there is also a lack of correlation between the severity on imaging versus the symptom severity reported by patients. MRI or CT myelography with axial loading may be a useful adjunct to routine imaging.

Electromyography and nerve conduction studies (EMG) are also used to aid the diagnosis of diagnosis [11], as this distinguishes polyneuropathy, radiculopathy or other peripheral nerve disorders from lumbar spinal stenosis. EMG exams are often normal in patients with lumbar spinal stenosis.

Treatment / Management

Management for lumbar spinal stenosis is aimed at reducing symptoms and improving functional status. Conservative treatment is the first-line treatment for this condition. Conservative treatment options include physical therapy, oral anti-inflammatory medications, and epidural steroid injections. Although there is no standardized physical therapy regimen, many therapists focus on stretching and strengthening of the core muscles, which can lead to correction of posture and improved symptom [12]. Although there are short-term benefits, lumbar epidural steroid injections have not been shown to have long-term improvement of pain and disability in lumbar spinal stenosis patients, and there is no statistical difference between epidural injections with anesthetics alone versus a mixture of anesthetics with corticosteroids [13]. Lumbar corsets may also be trialed for temporary relief of pain [14].

Barring emergencies such as cauda equina syndrome, surgical management for lumbar spinal stenosis is usually elective, as the goal of treatment is to improve function, rather than preventing neurologic impairment. The most frequently performed surgical procedure is laminectomy. A randomized trial has shown that there is a greater improvement of symptoms in patients undergoing laminectomy compared to the non-surgical group [15], however, the symptom improvement between the surgical and non-surgical groups diminish over time. Laminectomy with fusion is typically reserved for patients with concurrent spondylolisthesis to provide further stability. A less invasive approach is interspinous spacer implantation, this procedure is appropriate for patients with intermittent claudication symptoms without spondylolisthesis.

Differential Diagnosis

Differential diagnoses for lumbar spinal stenosis include, but not limited to, peripheral vascular disease (vascular claudication), cauda equina syndrome, nonspecific low back pain, degenerative disc disease, spondylosis, malignancy, infection, radiculopathy, distal polyneuropathy, osteoarthritis, inflammatory arthritis, spinal cord vascular malformations, and tethered cord syndrome.

Prognosis

Lumbar spinal stenosis is a significant cause of pain and disability, and approximately half the patients have involvement of other spinal segments over time; however, it typically follows a benign course. In one cohort study, 30% of patients electing to manage lumbar spinal stenosis with non-surgical procedures eventually requested for surgical management, and approximately 19% of patients who had an initial surgery eventually underwent a repeat surgery [16].

Enhancing Healthcare Team Outcomes

Lumbar spinal stenosis is a common disease process in the outpatient setting. These patients have symptoms such as leg pain and low back pain. The cause of this condition is most likely secondary to chronic wear-and-tear damages to the vertebral column. Despite imaging studies can show there is indeed lumbar spinal stenosis, the patient's may or may not have corresponding symptoms. Because there is no evidence to demonstrate the superiority of surgical versus non-surgical treatments of lumbar spinal stenosis, it is important to take a multidisciplinary approach [3] (Evidence level I). Primary physicians must recognize the patient's presentation, the care of the patient must be coordinated with PM&R, pain management, orthopedist, and/ or neurosurgeons (if there is a neurosurgical emergency). Physical therapists must also be involved as physical therapy is the mainstay in the conservative treatment of this condition. In patients who need to undergo surgical treatment, the nursing staff must be aware of the patient's medical status. In short, the care of patients suffering from lumbar spinal stenosis requires a team-based cooperative model.