The Correlation of High Signal Intensity Zones on MRI & Low Back Pain

While the presence of a disc herniation can be confirmed on MRI, what has proven to be more difficult is identifying the potential source of other discogenic pain that is not as visible on a standard MRI.

In 1992, a paper was published in which the authors claimed that ‘High Intensity Zones’ (HIZ), as visualized on T2 weighted MRI’s, were 90% predictive that the disc will show a grade 4 disruption on discography.[1] Aprill & Bogduk also claimed that 90% of these HIZ signs would test positive for concordant pain on provocative discography and that 82% of all concordant discs tested on provocative discography will have a HIZ sign on MRI (this data was based on 500 consecutive MRI’s of patients with lower back pain bad enough to warrant an MRI; 143 HIZ were discovered).  However, current standards of practice for assessing disc injuries no longer includes discography as it has been shown that inserting a needle in the good “control” disc can lead to degenerative changes of that disc overtime.

HIZ are defined as small foci of high signal intensity at:

• Mid-sagittal T2-weighted images
• Or contrast enhancement T1-weighted images near the vertebral endplates[2]

Studies show that the HIZ represents fluid or mucoid material from the nucleous pulposus which fills each annular tear; this material is trapped between the lamellae of the annulus fibrosus, between torn fibers of the outer annulus or underneath the posterior longitudinal ligament complex.  The annulus fibrosus becomes inflamed and HIZ is associated with granulated tissue and new blood vessels, which results in the characteristic signal abnormality.[3]

HIZ tears or fissure can be as painful as a herniated disc but not as easily detectable because the pathology is more subtle on imaging.  However, it is now established that a tear or fissure can be:

• separations between annular fibers;
• separations of annular fibers from their vertebral insertions; or
• breaks through these fibers in any orientation involving one or more layers of the annular lamellae.[4]

The HIZ research and its conclusions have been questioned by several studies,[5]  and HIZ has also been confirmed by several other studies.[6]  Clinically, many specialists will not consider a HIZ finding conclusive of a painful disc and that a patient’s symptoms and other clinical findings must be interpreted all together.

In the medical-legal context in a personal injury case, if there is a MRI finding of a HIZ sign, it is crucial to tie that findings to the patient’s history and findings on physical examination.  In Washington State, any medical opinion that connects objective findings, such as HIZ, to subjective pain complaints needs to satisfy the medical-legal standard that the opinion is generally accepted within the scientific community (also known as the Frye-standard).

The attorneys at Adler Giersch, PS understand the importance of HIZ findings on MRI and its correlation to musculoskeletal pain.  And we understand the evidentiary proof standards that turn established examination findings into a diagnosis.  We are ready to assist in tough advocacy for your patients.