A 34-year-old man complained of inflammatory back pain, alternating buttock pain and restriction in spinal mobility. Therefore, the man was referred for a full spine MRI examination.
Sagittal T1-weighted (Fig. 1) MR image shows a high-signal intensity in the intervertebral disc space of T8-T9. At the same level at the posterior aspect, there is a syndesmophytic ankylosis. All other intervertebral discs show a normal signal intensity and there are no abnormalities in vertebral stature, alignment and bone marrow signal.
Ankylosing spondylitis (AS) belongs to the family of spondyloarthritis (SpA). It is a chronic inflammatory disease causing axial arthritis, frequently resulting in inflammatory low-back pain and alternating buttock pain early in the disease course. Eventually, severe impairment of spinal mobility occurs, due to structural changes ultimately leading to fusion (ankylosis) of the spine and sacroiliac joints.
There is a male predilection and it usually manifests in young adults, with the first symptoms often becoming evident in the third decade. [1-5]
Ankylosing spondylitis predominantly affects the spine and sacroiliac joints by inflammation. Since magnetic resonance imaging (MRI) allows for early detection of inflammatory changes, it is the first choice of imaging for early diagnosis of ankylosing spondylitis. [1-3] If untreated AS may cause significant morbidity as the structured lesions will progress. Early diagnosis is particularly important as newer therapies are able to contain this condition and even induce remission.  When a physician has a patient with a suspected diagnosis he should refer for MRI. [1,3]
The key findings on MRI are localised in the spine and sacroiliac joints. Namely inflammatory or fatty Romanus lesions of the spine (early spondylitis), a high-signal intensity on T1-weighted MR images in the intervertebral disc associated with new bone formation, syndesmophytes, diffuse syndesmophytic ankylosis ("bamboo spine"), Andersson lesion and sacroiliitis [1,2,4].
The T1-weighted high-signal intensity in the intervertebral disc and the syndesmophytic ankylosis in combination with the clinical presentation (male, 34-year-old, inflammatory back pain, alternating buttock pain and restriction in spinal mobility) lead to the diagnosis of ankylosing spondylitis.
Take Home Message / Teaching Points:
When present in a patient with inflammatory back pain, an intervertebral disc high-signal intensity on T1-weighted MR images can be a sign of the presence of ankylosing spondylitis. [1,2]
Written patient consent for this case was waived by the Editorial Board. Patient data may have been modified to ensure patient anonymity.
 Laloo F, Herregods N, Jaremko JL, Carron P, Elewaut D, Van den Bosch F, Verstraete K, Jans L (2018) New bone formation in the intervertebral joint space in spondyloarthritis:An MRI study. Eur J Radiol 109:210-217. (PMID: 30527307)
 Malghem J, Lecouvet FE, François R, Vande Berg BC, Duprez T, Cosnard G, Maldague BE (2005) High signal intensity of intervertebral calcified disks on T1-weighted MRimages resulting from fat content. Skeletal Radiol 34(2):80-6. (PMID: 15480646)
 Malaviya AP, Ostor AJ (2011) Early diagnosis crucial in ankylosing spondylitis. Practitioner 255(1746):21-4, 2. (PMID: 22272527)
 Sharma R, Gaillard F; et al. Ankylosing spondylitis. Radiopaedia. 2019 [cited 22/05/2019]. Available from: https://radiopaedia.org/articles/ankylosing-spondylitis?lang=us
 T Yu D, van Tubergen A. Clinical manifestations of axial spondyloarthritis (ankylosing spondylitis and nonradiographic axial spondyloarthritis) in adults. UpToDate. 2018 [cited 22/05/2019]. Available from: https://www.uptodate.com/contents/clinical-manifestations-of-axial-spondyloarthritis-ankylosing-spondylitis-and-nonradiographic-axial-spondyloarthritis-in-adults?search=ankylosing%20spondylitis&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1