Central spinal canal stenosis may be developmental, acquired, or a combination of the two. Developmental stenosis is relatively uncommon and is estimated to account for approx 15% of all cases of spinal stenosis. It may be idiopathic or related to a more generalized disorder affecting the skeletal system, as in the case of the mucopolysaccharidoses or Down's syndrome. The idiopathic variant may selectively involve the lumbar region or may be generalized. It results from the formation of short pedicles with a resulting decrease in the cross-sectional diameter of the central canal. In isolation, this abnormality is generally not symptomatic but renders the patient more susceptible to relatively mild derangements of the disc or posterior elements. Acquired central spinal stenosis may be caused by various abnormalities related to degeneration of the intervertebral disc (vertebral osteophyte, circumferential disc bulge, focal disc protrusion or extrusion), facet joints (osteophyte, synovial cyst, or spondylolisthesis), and hypertrophy of the ligamentum flavum. Clinical presentation is nonspecific and includes back pain and radiculopathy that despite impressive imaging findings may be asymptomatic. The clinical consequence of more severe stenosis is a syndrome of neurogenic or spinal claudication, related to compression of the nerve roots of the cauda equina. The symptoms are typically bilateral and include back pain, sciatica, lower extremity parasthesias, and motor weakness, which tend to be exacerbated on standing or walking and improved with lying flat or sitting, particularly with flexion. The straight leg raise sign is frequently absent and sensory changes are often nondermatomal owing to the typically diffuse nature of disease. Bowel, bladder, and sexual dysfunction are late manifestations. Axial T2-weighted MR images are the best noninvasive way to evaluate the degree of central canal stenosis. CT and CT myelography are comparable techniques (14).
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