Lumbar Spinal Stenosis Caused by Degenerative Spondylolisthesis

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Lumbar Spinal Stenosis Caused by Degenerative Spondylolisthesis

Lumbar spinal stenosis is a condition characterized by the narrowing of the spinal canal in the lower lumbar region. This narrowing can put pressure on the spinal cord and the nerves that travel through the lumbar region, leading to a variety of symptoms such as pain, numbness, weakness, and tingling in the legs. Lumbar spinal stenosis is a major contributor to disability among the elderly population, ranking as the primary reason for spinal surgery in individuals aged 65 and older.

The precise causes of lumbar spinal stenosis can differ from one individual to another, often involving a combination of various factors. These include:

• Age-related progressive spinal degeneration (spondylosis) leading to spinal canal narrowing due to the accumulation of bone spurs (osteophytes)
• Spondylolisthesis
• Thickening of spinal ligaments (e.g., ligamentum flavum hypertrophy)
• Degeneration of the intervertebral discs
• Herniated or bulging discs which reduce the available space within the spinal canal
• Facet joint osteoarthritis leading to the growth of osteophytes and the narrowing of the spinal canal
• Spinal trauma such as fractures or dislocations which can cause the spinal canal to narrow if they result in the displacement of bone or other structures within the canal
• Spinal tumors which can arise and compress the spinal cord or nerves, leading to stenosis
• Congenital or developmental causes

The signs and symptoms in individuals suffering from lumbar spinal stenosis vary considerably. They range from an absence of symptoms to low back pain alone, to low back pain with radicular symptoms, and to neurogenic claudication (symptoms brought on by walking). Signs and symptoms arising from facet arthrosis and disc disruption further vary the clinical findings. Neurogenic claudication in individuals with spinal stenosis stems from either ischemia or the mechanical compression of nerve roots. Neurogenic claudication is typically linked to central canal stenosis, while radiculopathy tends to develop due to nerve encroachment at the lateral recess.

Degenerative Spondylolisthesis

There are several types of spondylolisthesis. However, the most common types include:

• Isthmic (occurs in young individuals and is typically caused by a defect or fracture of the pars interarticularis)
• Degenerative (occurs in the elderly)

Degenerative spondylolisthesis is rarely seen before the age of 50 and affects females more commonly than males. With respect to lumbar spinal stenosis, age-related progressive spinal degeneration leads to a narrowing of the central spinal canal, the lateral recesses, and the neural foramina. This can be further complicated by the presence of degenerative spondylolisthesis.

Degenerative spondylolisthesis is defined by the North American Spine Society as “ … an acquired anterior displacement of one vertebra over the subjacent vertebra, associated with degenerative changes, without an associated disruption or defect in the vertebral ring.”

Degenerative spondylolisthesis is considered to be caused by habitual or occupational activities that require the spine to be in a flexed position. This condition most typically affects the L4-L5 segment, occurring at a rate 6 to 9 times greater than that of other lumbar regions. The incidence of degenerative spondylolisthesis rises four-fold in the presence of L5 sacralisation. The forward slip rarely exceeds 30% of the AP diameter of the subjacent vertebral body and slippage is less severe in the presence of pronounced disc thinning. The anterior displacement is a consequence of arthrosis in facet joints that have a sagittal orientation such as those commonly found at the L4-L5 level.

The physical examination finding associated with spondylolisthesis is the prominence of the spinous process of one vertebra compared with those above. This is known as the “step defect”. In the case of degenerative spondylolisthesis, the step defect results from the anterior slip of an entire vertebral segment relative to the subjacent vertebra. However, in the isthmic form of spondylolisthesis, the vertebra involved separates into two parts allowing only the anterior portion to slide forward while the posterior arch and spinous process remain in position. Since degenerative spondylolisthesis typically affects L4 while isthmic spondylolisthesis typically affects L5, the resulting step defect is found at the same level in both types.

• Progressive development of low back pain and stiffness
• Symptoms of neurogenic claudication:
• Pain and weakness in the thighs and calves
• Numbness and/or paraesthesia in the lower extremities
• Pain that is worsened with walking (particularly downhill), standing, and lumbar extension
• Pain that is relieved with sitting and spinal flexion (e.g., when riding a bicycle and by leaning on a shopping cart, commonly referred to as the “Shopping Cart Sign”)
• Lower extremity symptoms are most commonly bilateral but may be asymmetric

• Reduced lumbar spinal motion
• Leg pain on passive and active lumbar extension
• A normal neurological examination (however lower extremity weakness, sensory loss, and/or reduced muscle stretch reflexes may be detected after a period of ambulation)
• Straight Leg Raise and Valsalva tests are typically negative
• Pain aggravated by the Lumbar Quadrant test
• Normal lower extremity pulses

While plain radiographs can demonstrate evidence of osteoarthritis and spondylolisthesis, Magnetic Resonance Imaging is the most appropriate imaging technique for the diagnosis of lumbar spinal stenosis, followed by a CT scan.

The following are examples of red flags for patients presenting with low back pain and lower extremity symptoms:

• Gradual onset and worsening of signs and symptoms of radiculopathy
• History of significant trauma
• Bilateral lower extremity symptoms
• Pronounced neurological impairment
• Bladder and bowel dysfunction
• Saddle anesthesia
• Severe tenderness on palpation or severe pain with any examination procedure
• Unexplained weight loss

If any red flags are identified during history taking and clinical examination, referral for urgent medical evaluation and further investigation is warranted.

Intermittent Claudication

Intermittent claudication can arise from two prevalent clinical conditions: lumbar spinal stenosis, which manifests as “intermittent neurogenic claudication,” and peripheral vascular disease, which induces “intermittent vascular claudication.” Claudication is a term used to describe discomfort, weakness, or numbness that typically arises during physical activity such as walking and subsides with rest. There are two primary forms of intermittent claudication: neurogenic and vascular.

Neurogenic Claudication

Neurogenic claudication is the more prevalent form of claudication linked to spinal stenosis. It occurs when the narrowing of the spinal canal exerts pressure on the nerves within the spinal cord, resulting in symptoms such as pain, weakness, numbness, or tingling in the lower back and legs. These symptoms tend to intensify when one is standing or walking, as assuming a fully upright position naturally leads to a narrowing of the spinal canal which, in turn, exerts added pressure on the nerve roots. Temporary relief from this pain can often be achieved by sitting or bending forward as these positions naturally widen the spinal canal and, therefore, alleviate the undue pressure on the nerve roots. Patients with neurogenic claudication have normal peripheral pulses and vascular studies.

• Location of Pain – Thighs, calves, and low back
• Aggravating Factors – Standing, walking, and lumbar extension
• Relieving Factors – Sitting and bending forward
• Leg Pulses – Typically normal
• Skin Changes – Usually absent

Vascular Claudication

Vascular claudication is less common than the neurogenic type and results from reduced blood flow to the legs due to the compression of peripheral blood vessels. Unlike neurogenic claudication, the symptoms of vascular claudication are associated with inadequate blood flow rather than nerve compression. Individuals with vascular claudication may encounter pain, cramps, or a sensation of heaviness in their legs (typically below the knees) during physical activity. While rest can provide relief from these symptoms, it often takes longer for them to subside compared to symptoms experienced by individuals with neurogenic claudication. Patients with peripheral vascular claudication present with the following: abnormal peripheral pulses and vascular studies, leg pain that is more severe than back pain after walking some distance, and pain that is relieved with rest. As vascular claudication is associated with blood flow issues, it necessitates vascular assessment and treatment. This could involve medications, lifestyle alterations, and/or vascular procedures aimed at enhancing blood flow to the legs.

• Location of Pain – Buttocks and calves
• Aggravating Factors – Any leg exercise
• Relieving Factors – Rest
• Leg Pulses – Reduced or absent
• Skin Changes – Pallor, cyanosis, and nail dystrophy

Natural Course and Diagnosis of Lumbar Spinal Stenosis

Below are recommendations on the natural course of lumbar spinal stenosis by the World Federation of Neurosurgical Societies’ Spine Committee:

• Approximately 30% of patients with lumbar spinal stenosis are expected to worsen, but 30% may improve with conservative measures.
• There are predictive signs/symptoms that these patients will worsen:
  • Dural sac cross-sectional area <50 mm
  • Presence of radicular symptoms and back pain
  • Presence of degenerative spondylolisthesis and/or scoliosis
  • Symptom duration >1 year