A Workers’ Compensation Adjuster’s Guide to Acute vs. Chronic Injuries

Understanding T2 and STIR MRI Findings

In my training as a Physician’s Assistant, and while working in orthopedic surgery, there are aspects of our education, training and experience that become second nature. However, at times, we tend to overlook the importance of what is perceived as routine everyday use, and the value of these data points is lost on the general population.

One of these items is the component of every MRI discussing T2 and STIR changes noted. We are often asked to explain what these findings are and how they can help me in the adjudication of a workers compensation file.

For those who are handling workers compensation findings these two components of every MRI are crucial for making informed decisions about the identified event. The T2-weighted imaging and STIR (Short Tau Inversion Recovery) studies provide that clinical data necessary about tissue changes to learn if this is an acute or chronic condition. Having this information clearly affects all of the parameters of the claim. In short, acute is yours, chronic is not.

What Are T2 and STIR Sequences?

With every injury, there is a natural response on the part of the body to attempt to heal. As part of this healing process, the body delivers fluid to the area in terms of edema, swelling, hematoma, and other processes to initiate and potentiate tissue healing. The T2-weighted images highlight fluid accumulation and inflammation within tissues. As noted, MRI algorithm, particularly with the T2 images, water appears bright (or white) and demonstrates the presence of acute findings. Additionally, STIR sequences are sensitive to detecting fluid and information while suppressing those signals from fat, enhancing the contrast enabling the reviewer to more easily identify more subtle tissue changes. The presence of increased T2 or STIR signals objectifies the presence of an acute injury.

T2 Findings in Acute Injuries:

If you are looking at the films, the T2 findings will demonstrate themselves as a bright signal intensity at the site of the reported injury indicating tissue edema or other information. These well-defined areas at the site of the injury should correlate with the reported mechanism of injury and location of symptomology objectifying if the compensable injury did cause damage or harm to the physical structure of the person.

As an example, a muscle strain appears as hyperintense streaks within the muscle fibers. A joint effusion is demonstrated as a right mass within the joint. And interestingly enough disc herniations also demonstrate as an increased signal intensity differentiating between a chronic disc lesion and an acute disc herniation. These specific findings would support whether the pathology suggested is a function of the date of injury or not.

STIR Findings in Acute Injuries:

An additional parameter would be that STIR findings are particularly sensitive in the detection of bone marrow edema which is another indicator of a significant acute insult to the body part. Moreover, this particular sequence can establish if there is soft tissue inflammation, acute fractures, ligament tears, and is a more superior detection protocol for subtle muscle injuries that may or may not be identified with the T2-weighted studies.

This particular study is a key factor when a diagnosis of a ligament sprain of the lumbar spine is reported or if multiple subluxations are suggested in the diagnosis list. Minimizing the extent of the accepted compensable injury to what actually occurred is key in the handling of workers compensation files.

Chronic Injury Patterns

Chronic conditions present differently, reflecting long-term tissue changes and healing responses rather than active inflammation.

T2 Findings in Chronic Conditions:

To be clear, there will be T2 signal changes in chronic conditions. What this means is that if there is a variable signal, the degree of acuteness can be ascertained relative to the severity of this finding. Scar tissue, another indication of chronicity, shows as a very low signal. Chronic disc degeneration also shows with a decrease in signal intensity thereby establishing the pathology is not a function of a recent injury.

STIR Findings in Chronic Conditions:

If the findings noted on the STIR sequencing are absent, or perhaps minimal, this is a signal of a truly chronic condition.

Clinical Application for Adjusters

The timing and intensity of signal changes on T2 and STIR sequences provide objective evidence about injury acuity. If the identified pathology is acute, the signals would be very bright on both sequences. However, if there is no reported finding, this is a clear clinical indication that you can objectively ascertained no acute injury to that particular body part occurred with respect to the noted date of injury.

Conclusion

With the stronger magnets currently being used in MRI studies, tempered by the modifications to the algorithms employed, T2 and STIR MRI findings serve as powerful tools for distinguishing acute from chronic conditions in workers’ compensation cases. Bright signal intensity on both sequences typically indicates recent injury with active inflammation, supporting the notion that the injury identified is a function of the date of injury. As noted, normal or low signal intensity establishes the identified pathology as not being acute. Taking into account what the radiologist reports (or do not report) is an objective basis for establishing the consequences relative to the compensable event.