Table 2

Locations and descriptions of inflammatory changes

Type of lesionDescriptionTechnical facts
Anterior/posterior spondylitis (figures 2 and 3)▶Typically located within bone marrow at one or more of the four corners of vertebral bodies▶T1w: usually low signal intensity
▶STIR: high signal intensity
▶Often shaped triangular if located at a corner, but may also involve the whole vertebra (MIL*)
▶(CIL*, RL)
Spondylodiscitis (figure 4)▶Located within bone marrow at cortical plate adjacent to intervertebral disc▶T1w: usually low signal intensity
▶Often hemispheric shape▶STIR: high signal intensity
▶Frequently at both sides of the intervertebral disc
▶Usually confined to vertebral body and disc and does not spread to surrounding soft tissues
Arthritis of CV joints (figure 5)▶Any CV joint from T1 to T12 may be involved▶T1w: low signal intensity
▶Associated with bone marrow oedema near CV joint, extending to pedicles, posterior aspect of vertebral bodies (lateral of spinal canal) and neighbouring rib▶STIR: high signal intensity
▶Only visualised on lateral slices (not showing spinal canal)
▶Additional axial and/or coronal slices may give additional information
▶(Included in definition of LIL*)
▶Note: Arthritis of costotransverse joints usually not detected on sagittal images
Arthritis of zygoapophyseal joints (facet joint arthritis) (FIL*/PIL*) (figure 6)▶Any facet joint from C2 to S1 may be involved▶T1w: low signal intensity
▶Usually associated with bone marrow oedema within spinal pedicles (posterior of spinal canal)▶STIR: high signal intensity
▶Additional axial and/or coronal slices may be necessary▶Only visualised on lateral slices (not showing spinal canal)
▶Surrounding soft tissue oedema may occur
Enthesitis of spinal ligaments (figure 7)▶Direct evidence of inflammation can be frequently seen in the supraspinal ligament, interspinal ligaments and the ligamenta flava▶T1w: low signal intensity
▶ STIR: high signal intensity
▶Inflammation of affected ligaments is usually associated with bone marrow oedema of adjacent bone (eg, spinous process)▶Note: T1w/Gd FS may give additional information to judge the extent of lesion
▶Signal changes of paraentheseal soft tissues (eg, musculature) may occur
▶Included in the definition of PIL*
  • * Abbreviations of the Canada–Denmark MRI in ankylosing spondylitis working group47 are given for reference.

  • RL, Romanus lesion according to Bennett et al11 (see comment in the text). Each of the inflammatory lesions described must be visible in at least two or more consecutive sagittal slices.

  • CIL, corner inflammatory lesion; CV, costovertebral; LIL, lateral inflammatory lesion; MIL, massive inflammatory lesion; NIL, non-corner inflammatory lesion; PIL, posterior element inflammatory lesion; STIR, short τ inversion recovery; FIL, facet joint inflammatory lesion.