Sean Crowther MBBCh, Presenter: Nothing to Disclose

Robert G. W. Lambert MBBCh, Abstract Co-Author: Nothing to Disclose

Barbara Spady PhD, Abstract Co-Author: Nothing to Disclose

Walter P Maksymowych MD, Abstract Co-Author: Nothing to Disclose

Sukhvinder Dhillon MBChB, Abstract Co-Author: Nothing to Disclose

To document the distribution of posterior element inflammation in active Ankylosing Spondylitis (AS) and determine whether it is independent of vertebral body edema.

MRI of the spine was performed at baseline on 26 subjects (20 male,mean age 42yrs) with clinically active AS recruited to clinical trials of biologic agents and on 3 control volunteers. Using sagittal STIR sequences, the presence of increased signal in bone marrow was recorded at each level in the spine from C1 to S1. Bone marrow edema (BME) was recorded as present or absent for the vertebral body (VB) and separately for posterior elements (PE) including pedicle, facet, transverse and spinous processes. Scans were randomized and scored independently by two radiologists blinded to diagnosis. Results were analyzed by spinal region (cervical, thoracic and lumbar including S1) and vertebral level. Prevalence of BME in posterior elements was compared to vertebral bodies using a paired t-test. Relationship of VB and PE edema was analyzed, by level, using a chi-square test.

PE edema was observed in all regions in AS patients with and without the presence of VB edema. The distribution of PE edema was shown to be independent of VB edema in all 3 regions (p<0.01). The mean number of levels with PE edema was (SD): cervical 0.8 (1.2), thoracic 4.8 (3.9) and lumbar 1.2 (1.6).A significant difference in prevalence was only noted in the lumbar region (p=0.02) with VB edema more common. PE edema was not observed in any control subjects. In one patient, PE edema was the only manifestation of disease. Within the posterior elements, spinous or transverse process edema was common in the thoracic spine and was observed in 25/26 patients whereas thoracic VB edema was seen in only 21 patients.

BME of the posterior elements is common in clinically active AS with similar prevalence to vertebral body BME in cervical and thoracic regions.Posterior element BME occurs independently of vertebral body BME and may be the only MRI manifestation of active disease in the spine.

Published MRI methods of scoring AS activity exclude PE disease. These scoring systems may underestimate the number of affected levels or extent of BME.

Crowther, S, Lambert, R, Spady, B, Maksymowych, W, Dhillon, S, MRI of Vertebral Inflammation in Ankylosing Spondylitis: Is Posterior Element Involvement Independent of Vertebral Body Edema?.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4435819.html