What does a rheumatologist need to know about a lumbar spine Magnetic Resonance (MR) imaging study in a patient with psoriasis?

From the Guidelines

A rheumatologist examining a lumbar spine MRI of a psoriatic patient primarily wants to identify signs of psoriatic spondyloarthritis, focusing on detecting inflammatory changes at the sacroiliac joints and spine, including bone marrow edema, erosions, ankylosis, syndesmophytes, facet joint involvement, enthesitis, and paravertebral soft tissue inflammation, as these findings help determine disease activity, extent of structural damage, and guide treatment decisions, potentially indicating the need for biologics like TNF inhibitors, IL-17 inhibitors, or IL-23 inhibitors if axial disease is confirmed 1.

When evaluating the lumbar spine MRI, the rheumatologist should consider the following key points:

• Inflammatory changes at the sacroiliac joints and spine, including bone marrow edema, erosions, and ankylosis, which are hallmarks of axial involvement in psoriatic arthritis 1
• Syndesmophytes (bony outgrowths), which in psoriatic arthritis tend to be asymmetric and chunky compared to the more symmetric, fine syndesmophytes seen in ankylosing spondylitis 1
• Facet joint involvement, which can be more prominent in psoriatic arthritis than in other spondyloarthropathies 1
• Enthesitis at spinal ligament attachments and paravertebral soft tissue inflammation, which are important findings in psoriatic spondyloarthritis 1

The rheumatologist should also be aware of the latest recommendations for the management of psoriatic arthritis, including the use of biologics like TNF inhibitors, IL-17 inhibitors, or IL-23 inhibitors, which may be indicated if axial disease is confirmed 1.

In terms of imaging, MRI of the sacroiliac joints and spine is the preferred imaging modality for evaluating suspected axial spondyloarthritis, as it can detect inflammatory changes and structural damage 1. The decision to image the spine as well as the sacroiliac joints should be based on the site of symptoms, and whole-spine or whole-body MRI may be useful in identifying the burden of disease throughout the spine 1.

Overall, the rheumatologist should take a comprehensive approach to evaluating the lumbar spine MRI, considering both the clinical and imaging findings to guide treatment decisions and optimize patient outcomes.

From the Research

Key Considerations for a Rheumatologist

When evaluating a lumbar spine MR of a psoriatic patient, a rheumatologist would want to know:

• The presence and extent of axial involvement, including sacroiliitis and/or spondylitis, as axial involvement occurs in 25% to 70% of patients with psoriatic arthritis (PsA) 2
• The clinical presentation, imaging characteristics, and differential diagnoses of axial PsA, as there are no agreed-upon classification or diagnostic criteria for axial involvement in PsA 2
• The results of spinal mobility measurements, such as the modified Schober test, lumbar side flexion, and cervical rotation, which can help assess spinal involvement in PsA 3
• The presence of inflammatory spinal symptoms or radiological sacroiliitis and other radiographic signs of spondylitis, which can aid in diagnosis 4
• The presence of cervical spondylitis, which has been reported in 35% to 75% of patients with PsA 5

Imaging Characteristics

A rheumatologist would also want to know:

• The MRI appearance of the sacroiliac joints, including the presence of bone marrow edema (BME), bone erosion, backfill, or ankylosis, which can increase the likelihood of axial spondyloarthritis (axSpA) 6
• The pattern of BME, including its extent, depth, and relation to other lesion types, which can help distinguish axSpA from differential diagnoses 6
• The presence of structural lesions, such as bone erosion or ankylosis, which can increase the specificity of axSpA diagnosis 6

Diagnostic Challenges

A rheumatologist should be aware of the challenges in diagnosing axial PsA, including:

• The lack of agreed-upon classification or diagnostic criteria for axial involvement in PsA 2
• The similarity in MRI appearance between axSpA and other diseases, such as degenerative disease or athletic injuries 6
• The need for further research to optimally distinguish axSpA from differential diagnoses 6