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Spinal stenosis

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Refers to the narrowing of the spinal canal with encroachment of the neural structures by surrounding bone and soft tissue.

15% of patients improve, 70% remain stable and 15% have deterioration over 4 years.

Most common reason for lumbar surgery in adults over the age of 65 years.

Estimated that as many as 400,000 Americans have symptoms of lumbar spinal stenosis.

Patients typically present with neurogenic claudication consisting of pain in the buttocks or legs when walking or standing that resolves with sitting or lumbar flexion.

Imaging studies can frequently indicate the presence of spinal stenosis in asymptomatic patients.

Patients have pain with extension of the lumbar spine.

Lumbar spinal stenosis syndrome involves lower extremity pain, numbness or weakness in the presence of low back pain.

The radicular pain due to spinal stenosis is probably related to the inhibition of normal nerve root vascular flow with resultant nerve root nutrition, nerve root edema, and nerve root dysfunction.

Diagnosis of lumbar spinal stenosis syndrome requires the presence of characteristic symptoms and signs and radiographic or anatomic evidence of narrowing or stenosis of the lumbar spinal canal.

The most common symptom associated with lumbar spinal stenosis is neurogenic claudication.

Neurogenic claudication refers to pain or other discomfort associated with walking or prolonged standing, with radiation into one or both lower extremities and is typically relieved by rest or lumbar flexion.

Neurogenic claudication is associated with radiating pain to the buttocks, thighs, lower legs, or feet.

Improvement in pain associated with sitting or lumbar flexion and worsening with lumbar extension.

Some patients experience no pain but have weakness, abnormal sensations, fatigue of the lower extremities along with sensory and gait impairment.

Radicular and polyradicular pain may occur with lumbar spinal stenosis and such discomfort may not be provoked by standing or walking.

Subtypes of clinical syndrome may overlap.

Surgery for lumbar spinal stenosis typically performed for lower extremity pain and not for relief of back pain.

Stenosis may occur at the central spinal canal, under the facet joints, or in the lateral foramina.

Spinal stenosis is most commonly due to acquired degenerative anatomical changes.

 

Spinal stenosis may be present at birth as seen in achondroplasia, spina bifida, and certain mucopolysaccharidoses.

 

Spinal stenosis changes include combination of abnormalities including: disc bulging, disc herniation, osteoarthritic facet joint hypertrophy, and hypertrophic ligamentum flavum changes.

 

Extended spines exhibit 15% less cross-sectional area of the intervertebral foramina, and nerve root compression is present one-third of the time.

 

 

The  dynamic changes in the shape of the spinal canal are more pronounced in individuals with spinal stenosis. 

 

 

The amount of narrowing may be 67% in lumbar spinal stenosis  compared to 9% in healthy spines.

 

Although central spinal stenosis leads to neurogenic claudication symptoms, and lateral recess or foraminal stenosis leads to radicular symptoms, diverse clinical presentations can be seen with similar radiographic changes.

Radiographic prevalence in a community-based population of adults aged 60-69 years was 47% for relative radiographic findings with sagittal diameter of 12 mm or less, and 19% for absolute radiographic lumbar spinal stenosis with sagittal diameter of 10 mm or less.

Mild stenosis classified as a narrowing of the normal central canal cross-sectional area by one third or less, moderate stenosis by between one third and two thirds, and severe stenosis as more than two thirds (Lurie JD et al).

The prevalence of radiographic lumbar spinal stenosis using qualitative criteria in adults 55 years of age or older who are asymptomatic is estimated at 21%-30% from moderate stenosis and 6-7% for severe stenosis (Tong HC etal).

The above data indicate that radiographic MRI imaging suggesting lumbar spinal stenosis is common in asymptomatic patients and this underscores the importance of clinical diagnosis made by history and physical examination.

Lower extremity pain with or without low back pain may be found in other spinal disorders, and extra spinal musculoskeletal disorders, other than the syndrome of lumbar spinal stenosis.

Differential diagnosis for older patients with lower extremity pain with or without low back pain include: spinal disorders such as lumbar sacral radicular pain from nerve root infringement, referred pain from lumbar spine structures, and lumbar vertebral compression fractures, musculoskeletal abnormalities such as hip joint pain, sacroiliac joint pain, trochanteric bursitis, piriformis syndrome, muscle strain or tears, myofascial pain, intermittent claudication from peripheral arterial disease, compartment syndrome, peripheral neuropathy and visceral referred pain.

Lumbar spinal stenosis syndrome is the most frequent indication for spinal surgery in individuals older than 65 years of age.

In lumbar spinal stenosis the absence of pain when seated, and improvement in pain when bending forward, and a wide based gait are findings that are most helpful in making a clinical diagnosis.

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