spinal stenosis

Spinal stenosis is a condition in which a portion of the spinal canal narrows to the point at which it can exert pressure on the nerves that travel through the spine.

Spinal stenosis is not to be confused with foraminal stenosis which is the narrowing of the foramina with subsequent compression of the nerve roots.

Epidemiology

The most commonly affected area is the lumbar spine (see lumbar spinal stenosis), followed by the cervical spine.

Men are more affected than women (except in the case of degenerative spondylolisthesis). Prevalence increases with age -most newly diagnosed patients are over the age of 50 years .

Pathology

Etiology

The causes of spinal stenosis can be divided into two groups :

  • bony structures
  • soft tissue structures
  • Acquired causes are more common than congenital ones, with the most common cause being osteoarthritis. Other causes include :

    • injuries: may fracture or inflame a part of the spine
    • tumors: spinal lesions, both benign and malignant, may cause spinal stenosis by compressing the cord
    • Paget disease of bone: a condition where bones grow abnormally large and brittle; when it involves a vertebra, there is resultant narrowing of the spinal canal and nerve compression
    Classification

    There are two main classification categories:

    • etiologic classification:
    • anatomic classification
      • central - cross-sectional area < 100 mm or < 10 mm AP diameter on axial CT
      • lateral - most commonly due to osteophyte formation
      • foraminal - between the medial and lateral border of the pedicle
      • extraforaminal - lateral to the lateral edge of the pedicle

    Radiographic features

    Plain radiograph
    • standing AP and lateral may show nonspecific degenerative findings (disc space narrowing, osteophyte formation)
      • less frequent are degenerative scoliosis and degenerative spondylolisthesis
    • flexion/extension radiographs may show segmental instability and subtle degenerative spondylolisthesis
    Myelography

    Plain radiographic myelography provides dynamic information such as the degree of cutoff when a patient performs extension.

    CT myelography

    Findings may include:

    • central and lateral neural element compression
    • bony anomalies
    • bony facet hypertrophy
    MRI

    Findings may include:

    • central stenosis, with the thecal sac measuring < 100 mm in area
    • obliteration of perineural fat and compression of lateral recess or foramen
    • facet and ligament hypertrophy
    • spinal stenosis may be incidentally discovered in asymptomatic patients