Imaging Spinal Stenosis

Kiran S. Talekar, MD; Mougnyan Cox, MD; Elana Smith, MD; Adam E. Flanders, MD


Appl Radiol. 2017;46(1) 

In This Article

Common Causes of Anatomic Narrowing

Disc Herniation

As previously discussed, disc herniations are an important cause or contributor to stenosis (Figure 15). Several interventional therapies focus on disc removal, and accurate, reproducible radiologic description is imperative for optimal surgical outcomes.

Figure 15.

(A) Axial T2-weighted image of L4-L5, where there is a disc protrusion. Note that the base of the herniation is wider than the diameter of the dome of the herniated disc. (B) Sagittal T2-weighted image of a disc extrusion (dome of the disc herniation being wider than the base) at L5-S1 causing obliteration of the CSF space in the thecal sac and nerve root compression.

Facet and Ligamentum Flavum Hypertrophy

Facet and ligamentum flavum hypertrophy frequently co-exist. Facet hypertrophy refers to bony overgrowth at the facet joints of the lumbar spine on a degenerative basis. The bony overgrowth may then result in narrowing of the lateral recess or neural foramen. Spinal canal compromise may also occur, when superimposed disc herniation and ligamentum flavum hypertrophy are present.

Ligamentum flavum hypertrophy or infolding refers to abnormal thickening and buckling of the ligamentum flavum as a result of degenerative changes in the lumbar spine. It is frequently bilateral and causes posterior obliteration of the CSF space in the thecal sac.

One important cause of cervical spinal canal stenosis that bears mention is ossification of the posterior longitudinal ligament (OPLL).[16] This diagnosis commonly co-exists with diffuse idiopathic skeletal hyperostosis (though not always), and is most easily appreciated on CT (Figure 16). In the cervical spine, OPLL may result in spinal injury after minor cervical trauma due to pre-existing cervical canal stenosis.

Figure 16.

(A) Sagittal noncontrast CT image of the cervical spine with ossification of the posterior ligament resulting in spinal canal stenosis. (B) Axial noncontrast CT of the cervical spine showing mushroom-shape of the OPLL causing spinal canal narrowing. (C) Sagittal T2-weighted image of the cervical spine in the same patient with spinal canal stenosis, obliteration of the CSF space around the spinal cord, and mass effect on the cord.