Definition

Lumbar spinal stenosis is classically defined as narrowing of the spinal canal, nerve root canals, or tunnels of the intervertebral foramina at the lumbar level. Lumbar spinal stenosis, when symptomatic, can cause a clinical syndrome of pain in the buttocks or lower extremities, with or without back pain. This is termed neurogenic claudication. However, a significant portion of the general population may have anatomic spinal stenosis without symptoms. Studies have indicated that 20% to 25% of asymptomatic people older than 40 years have significant narrowing of the lumbar spinal canal. Stenosis causes symptoms only when there is sufficient compromise of neural structures such as the cauda equina or nerve roots. This insult may be mechanical, vascular, biochemical, or neuropathic, and the reason for the condition reaching a symptomatic threshold is unclear. Therefore, spinal stenosis as a clinical entity is considered significant only if it results in symptomatic pain and compromised function.

The significant anatomic elements of the lumbosacral spine include the five lumbar vertebrae, L1-L5, the sacrum, the intervertebral discs, the ligamentum flavum, the zygapophyseal joints, the lumbar spinal nerve rootlets, the spinal nerve roots, and the cauda equina ( Fig. 50.1 ).

Normal anatomic structures of the lumbar spine at the third through the fifth lumbar levels. Note the close association between the nerve roots and the dural tube, the ligamentum flavum, the facet joints, the pedicles, and the lamina. The ligamentum flavum (interlaminar ligament) attaches laterally to the facet capsules.

Various schemes for classification of spinal stenosis have been devised and are listed in Table 50.1 .

Lumbar spinal stenosis has been found to affect more than 200,000 adults in the United States. There are numerous acquired types of spinal stenosis, but degenerative is the most common. The first stage in the degenerative process is generally degradation of the hydrophilic proteoglycans within the intervertebral disc, disc desiccation, and loss of disc height. This causes a shift of load onto the posterior structures of the canal, in particular the facet joints, which normally provide 3% to 25% of the support during axial loading, but may bear up to 47% with degeneration of the disc. As the facets bear more of the burden, they undergo degeneration, one aspect of which is osteophyte formation. This further diminishes the cross-sectional area of the canal and can also result in stenosis of the neural foramina (termed foraminal stenosis ). The ligamentum flavum undergoes buckling with decreased intervertebral disc height, leading to further encroachment of the canal. Epidural fat may contribute to reduced canal space in some patients. Patients can have degenerative facet synovial cysts that focally can encroach on the spinal canal and nerve rootlets and cause radicular pain.

Congenital lumbar spinal stenosis is less common, representing 9% of cases ; symptoms first appear in patients during their 30s. Patients with achondroplasia resulting in dwarfism often have stenosis secondary to hypoplasia of the pedicles. Acromegaly may cause spinal stenosis by enlargement of the synovium and cartilage, which results in decreased cross-sectional area of the canal. Symptomatic spinal stenosis secondary to purely isolated congenital causes is rare. More commonly, patients will have a combination of congenital and acquired stenosis; a developmentally smaller canal predisposes them to symptoms once acquired changes occur to the surrounding anatomy. Developmental factors that lead to a small canal include statistically significantly shorter pedicles and a trefoil-shaped canal.

Spinal stenosis can be differentiated by anatomic location, including central canal, lateral recess, foraminal, and extraforaminal ( Table 50.2 ). Additional subcategorization includes division of the lateral canal into three regions: entrance zone, mid-zone, and exit zone.

Symptoms

Patients with acquired lumbar spinal stenosis usually have symptoms during their 50s and 60s. Symptomatic lumbar spinal stenosis may result in both back pain (from axial components, such as facet degeneration) and leg pain (from radicular components of nerve root compression, either central or lateral). Leg pain is often greater than back pain, and depending on which nerve roots are impinged, leg pain can be unilateral or bilateral and monoradicular or polyradicular. Patients with acquired degenerative lumbar spinal stenosis tend to have a history of chronic low back pain and develop leg pain later in their course. In a study of 100 patients with lumbar spinal stenosis, back pain had been present for an average of 14 years and leg pain for an average of 2 years. The classic symptom of lumbar spinal stenosis is neurogenic claudication, also known as pseudoclaudication, which typically is manifested as buttock, thigh, and calf pain exacerbated with walking, standing, or lumbar extension and alleviated with sitting, lumbar flexion, or lying down with knees flexed. Symptoms also commonly involve cramping, numbness, tingling, heaviness, and spasms. As the spinal canal and neural foramina widen with flexion and become narrower with extension, pain often improves and walking tolerance increases with a flexed posture, such as while pushing a shopping cart or walking up an incline. From a diagnostic point of view, in one study, neurogenic claudication was found to have a sensitivity of 63% and a specificity of 71% compared with a combination of clinical, radiologic, and imaging test findings.

Symptoms that have been reported to have high sensitivity for lumbar spinal stenosis are as follows: best posture with regard to symptoms is sitting, worst posture with regard to symptoms is standing or walking, pain below buttocks, pain in legs worsened by walking and relieved by sitting, radiating leg pain, and age older than 65 years. Symptoms with high specificity for lumbar spinal stenosis include no pain when seated and symptoms improved when seated. A systematic review of the accuracy of the clinical history for the diagnosis of lumbar spinal stenosis, encompassing four studies and 741 patients, found that having no pain when seated, improvement of symptoms when bending forward, presence of bilateral buttock or leg pain, and neurogenic claudication were the most useful individual findings for identifying the syndrome of lumbar spinal stenosis.

Physical Examination

Unlike the history, no physical examination findings are considered classic for lumbar spinal stenosis. Abnormal findings in lumbar spinal stenosis are similar to those in other disorders that cause peripheral neurologic deficits. On physical examination, having a wide-based gait and an abnormal Romberg test result increase the likelihood of the clinical syndrome of lumbar spinal stenosis, whereas the absence of neurogenic claudication decreases the likelihood of the diagnosis. In a study of a 100-subject cohort, abnormal findings included sensory dysfunction, diminished deep tendon reflexes, positive Lasègue test result, and leg weakness, among others. Physical and functional findings with high sensitivity include longer recovery time after level versus inclined treadmill walking and no pain with lumbar flexion. Highly specific aspects of examination and testing include improved walking tolerance on inclined versus level treadmill, earlier onset of symptoms on level versus inclined treadmill, absent Achilles reflex, lower extremity weakness, pinprick or vibration deficit, wide-based gait, and presence of Romberg sign. Screening for peripheral arterial disease by ankle-brachial index and toe-brachial index tests should be considered in patients with intermittent claudication and lumbar spinal stenosis. A prospective study examining the rate of peripheral arterial disease in patients with intermittent claudication with concurrent lumbar spinal canal stenosis found that peripheral arterial disease was present in 26% of the subjects.

Functional Limitations

Worsening leg and back pain from walking, back extension, and prolonged standing is the primary contributor to activity limitation. As such, patients with lumbar spinal stenosis tend to have difficulties with walking long distances, walking down stairs, doing household work (e.g., dishwashing, vacuuming), and working overhead (which may induce spinal extension). Balance deficits from sensory deficits may increase fall risk.

Diagnostic Studies

Diagnostic studies must be interpreted in the context of the patient’s clinical presentation. Several studies have demonstrated that there is no correlation between radiologic findings and clinical or functional outcomes. The various qualities of the diagnostic tests are summarized in Table 50.3 .

Table 50.3

Comparison of Various Diagnostic Tests for Lumbar Spinal Stenosis

Imaging Method	Pertinent Findings	Advantages	Disadvantages	Accuracy
Plain radiography	Anteroposterior view: narrow interpedicular distance (normally 23–30 mm) Lateral view: decreased canal width Ferguson view: far-out syndrome Facet degeneration, cyst formation Ligamentum flavum ossification Intervertebral disc space narrowing Vertebral body end-plate osteophyte	Inexpensive Easy to obtain Can rule out gross bone disease	Poor soft tissue visualization	Sensitivity 66% and specificity 93% compared with plain CT as reference
Plain myelography	Ventral extradural defects: caused by disc protrusions and vertebral end-plate osteophytes Lateral or posterior extradural defects: caused by facet osteophytes Hourglass constriction: indicates central stenosis	Shows sagittal plane	Invasive May need several dye injections for high-grade stenosis Limited view of foramen Contraindicated in patients with contrast allergy, alcoholism, seizures, phenothiazine intake	71.8% correlation with surgical findings Sensitivity 54%–100%; equivocal compared with CT or MRI Specificity slightly higher than that of CT or MRI
Plain computed tomography (CT)	Fat plane obliteration at exiting root Canal shape (trefoil vs. round or ovoid) Pedicle length—direct measurement	Relatively inexpensive Axial view Superior bone detail	Poor soft tissue visualization Higher radiation exposure vs. other imaging techniques	83% correlation with surgical findings Sensitivity 74%–100%
Computed tomographic myelography	As above Useful in degenerative scoliosis or history of prior instrumentation	Visualization of central and lateral canals	Invasive Higher radiation exposure vs. other imaging techniques	Sensitivity 87% Comparable to MRI
Magnetic resonance imaging (MRI)	Disc degeneration: dark on T2 Annular tears: bright on T2 Stenosis and herniations in central and foraminal zones well visualized Evaluation of spine and spinal cord tumors	Noninvasive Shows sagittal plane Good soft tissue visualization	Interference from ferromagnetic implants Limitations on patient’s body size, need to lie still, claustrophobia Expensive and time-consuming	83% correlation with surgical findings Sensitivity 77%–87% Three-dimensional magnetic resonance myelography sensitivity 100% As accurate as CT myelography
Electrodiagnostics	Bilateral multilevel lumbosacral radiculopathy is most common diagnosis Paraspinal mapping electromyography score > 4 Tibial F wave and soleus H reflex latencies after exercise	Can evaluate for peripheral neuropathy and entrapments as well as progression of neurologic impairment Can rule out other neuromuscular disease	Significant interpretation bias May be difficult to differentiate lumbar spinal stenosis from other multiroot diseases (e.g., arachnoiditis) Patient discomfort or pain Expensive and time-consuming	Abnormal study in 78%–97% of patients with stenosis Paraspinal mapping electromyography score > 4: specificity 100% and sensitivity 30%

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

Glenohumeral Instability Extensor Tendon Injuries Lumbar Radiculopathy Bunion and Bunionette Temporomandibular Joint Dysfunction Pressure Ulcers

Stay updated, free articles. Join our Telegram channel

Join