Ankylosing spondylitis (AS) is a chronic, inflammatory type of arthritis that affects the spine and the sacroiliac joints. It can cause pain and stiffness in the spine, hips, and other joints. While an MRI is a common imaging test used to diagnose AS, it is possible for the condition to be missed on an MRI.
The primary signs of AS on an MRI include signs of inflammation, such as bone marrow edema and erosions, as well as structural changes like ankylosis and syndesmophytes. However, these changes may be subtle and can easily be missed, particularly in the early stages of the condition. Additionally, the presence of other conditions, such as osteoarthritis, can make it difficult to distinguish between the two.
In addition, an MRI may not be sensitive enough to detect the early stages of AS. In the early stages of the condition, the changes in the spine may be mild and may not be visible on an MRI. This is especially true for patients with AS who do not have a lot of inflammation in their spine.
Finally, an MRI may not be able to detect active inflammation in the spine, which is necessary to make a diagnosis of AS. This is because an MRI cannot detect the active inflammatory cells, which are responsible for causing the inflammation.
In summary, it is possible for ankylosing spondylitis to be missed on an MRI. This is because the changes associated with AS may be subtle, the presence of other conditions may make it difficult to distinguish between the two, it may not be sensitive enough to detect the early stages of AS, and it may not be able to detect active inflammation in the spine.