Inflammation in ankylosing spondylitis:: a systematic description of the extent and frequency of acute spinal changes using magnetic resonance imaging

Background: Magnetic resonance imaging (MRI) is increasingly used to detect inflammation in the spine of patients with ankylosing spondylitis ( AS). Objectives: To detect differentially the presence and extent of inflammation in the three spinal segments of patients with AS by MRI. Methods: In 38 patients with active AS, acute spinal lesions were assessed by T-1 weighted, gadolinium enhanced, spin echo MRI (T-1/Gd-DTPA) and short tau inversion recovery (STIR) sequences. MRI was quantified by the validated scoring system ASspiMRI-a. Acute spinal lesions were detected in the whole spine and in each spinal segment. One vertebral unit ( VU) was defined as the region between two virtual lines drawn through the middle of each vertebral body. Results: A greater number of inflammatory spinal lesions were found by the STIR sequence than by GdDTPA: inflammation was present in 30.6% of the VUs as assessed by STIR, compared with 26.8% of the same VUs assessed by T-1/Gd-DTPA. Inflammation was found more commonly in the thoracic spine ( TS) than in the cervical ( CS) or the lumbar spine (LS) with both techniques. When STIR was used, spinal inflammation in the CS, the TS, and LS was detected in 10/38 (26%), 28/38 (74%), and 9/38 (24%) patients, respectively. The VU T7/8 was found to be the VU most often affected by both techniques (27.8% by T-1/Gd-DTPA and 34.5% by STIR). Conclusions: Spinal inflammation is a common manifestation in patients with AS, and appears more frequently in the TS. The scoring system ASspiMRI-a can be used for evaluation of acute spinal changes in AS.