Magnetic resonance imaging so well-known simply as MRI has been around now for 35 years. We have a better sense of when to use them to diagnose and measure results of treatment. In this article, a group of Physical Therapists present how MRIs can be useful to the Physical Therapist in planning treatment and assessing outcomes. The specific focus is on magnetic resonance imaging of the spine. Reviewed in this context, the pearls and pitfalls of this tool are reviewed.
First, let's look at when MRIs are useful and what they show when directed toward the human spine. When you look at an MRI of the spine, you can easily see the bones, discs, spinal cord, ligaments, and even the cerebrospinal fluid in shades of black, white, and gray. Varying structures show up in different shades based on signal intensity picked up by the MRI.
MRIs are very helpful after trauma to the spine to look for neurologic damage. Likewise, vascular damage with blood loss or internal bleeding can be seen with MRIs. Pressure on the spinal cord or spinal nerve roots show up clearly. Injuries to the ligaments and other soft tissues can also be seen. Changes in size, shape, and orientation of the muscles are also visible. Any part of the spine from the head down to the tip of the spine (the coccyx) can be viewed.
The authors present the benefits (pearls) and disadvantages (pitfalls) of MRIs of the cervical spine (neck), thoracic spine (midback), and the lumbar spine (low back). As a diagnostic tool, MRIs help the Physical Therapist understand the underlying pathology. That's considered a clinical application.
But there's also room for using serial MRIs (several images of the same area taken at different time periods) to show the effect (or lack of effect) of treatment. This is the research application of MRIs. Though there is some expense involved in doing serial MRIs, there is also a high cost of health care when an ineffective treatment is applied over the course of weeks to months. Using imaging studies like MRI may offset the cost by providing information needed to guide treatment.
One of the best advantages of MRI (a pearl) is that it does not expose the body to ionizing radiation like X-rays and CT scans do. And it provides the only real way to look at the spinal cord. MRIs are better than X-rays for finding subtle or difficult-to-spot bone fractures. MRIs also show bone bruising and tumors that aren't readily seen on X-rays or CT scans.
One of the biggest downfalls (a pitfall) is the appearance of artifacts. Artifacts refer to anything that shows up on the MRI that isn't really there. An error on the part of the technician conducting the test can create artifacts. But so can the pulsations of blood or cerebrospinal fluid as they flow through the body.
Dental implants show up as dark spots. Fat and water in the body shift position causing artifacts. Even chemicals shifting in the body can become artifacts. Any of these factors creating artifacts can also result in a false positive meaning the MRI suggests a problem that doesn't exist.
One other pitfall to all imaging studies (including MRIs) is the fact that many people have changes that don't create symptoms. In fact, studies show that some of the damage to ligaments and other soft tissues associated with whiplash injuries are also present in people who have never injured their necks. On the other hand, it has been shown that some patients with severe neck or back pain have perfectly normal-looking imaging studies with no obvious damage to account for the symptoms.
In conclusion, MRIs offer some valuable information to the Physical Therapist. But all findings must be viewed with caution. The patient's history and clinical presentation (signs and symptoms) must be considered along with the imaging results when planning, assessing, and modifying treatment. Unless there is a strong suspicion of spinal fracture, infection, or tumors, or consideration of the need for surgery, MRIs may not be needed.
The use of MRIs in research to document changes in response to different treatments applied may be expanded in the future. As a research tool, MRIs show changes in muscle, soft tissues, and even at the cellular level. This can be valuable information for the Physical Therapist. Cost is the only deterrent since the patient is not exposed to any hazardous radiation. Continued advancements in improving MRI systems may also expand the use of this modality in both clinical and research applications.
Reference: James Elliott, PT, PhD, et al. The Pearls and Pitfalls of Magnetic Resonance Imaging for the Spine. In The Journal of Orthopaedic and Sports Physical Therapy. November 2011. Vol. 41. No. 11. Pp. 848-860.
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