HIgh Intensity Zone
What is a High Intensity Zone?
In relationship to the spine, it is a term that has been used on and off for the past 20 years.
Initially described by Drs’ April and Bogduk in 1992, it is a MRI finding identified on a specific sequence called T2. A High Intensity Zone (HIZ) is defined as an increased white signal in the margins of the disk annulus. Dr.’s April and Bogduk opined that it represented an acute annular disruption, and thus a source of pain. In the study (hyperlink above), presence of this signal intensity was associated with a painful grade 4 annular tear, and therefore, a reliable marker for back pain.
Armed with this information, many physicians utilized this sign as an indication for potential spinal fusion surgery. Unfortunately, the increased surgical rates did not yield better clinical outcomes. In plain English, this finding did not mean surgery would help.
In the December 2000 Article in Spine, by Dr. Carragee, the author wanted to compare the results of discography in patients with and without the findings of these High Intensity Zones (HIZ). His study concluded the following:
“The presence of a high-intensity zone does not reliably indicate the presence of symptomatic internal disc disruption. Although higher in symptomatic patients, the prevalence of a high-intensity zone in asymptomatic individuals with degenerative disc disease (25%) is too high for meaningful clinical use. When injected during discography, the same percentage of asymptomatic and symptomatic discs with a high-intensity zone were shown to be painful.”
This study was awarded the 2000 Volvo Award for Clinical Studies. And, this study may have identified why the clinical results of surgical management of HIZ lesions was less than predicted.
Since these early studies, there have been numerous studies on this topic. Some studies compared the “acuteness” of these findings. These studies suggest a HIZ lesion cannot be used to determine the recentness of the findings. In other words, HIZ cannot determine if the findings just developed, or was there for several years.
Other studies have even disputed the clinically significance of discography itself.
Not to be an alarmist, but recent studies suggest the act of discography on a normal disk (control level) will cause that disk to degenerate at a faster rate that if it had never have the study.
With all these controversies at hand, a prudent clinician needs to determine if the information is relevant to the individual patient. The clinician must also weigh the risks of the diagnostic procedure versus the benefit of the information.
In patients that are considering spine surgery, the great unknown is whether the findings on the studies are the true cause of the pain or dysfunction. That is because there is such a high prevalence of these findings in asymptomatic people. The surgeon, along with the patient, and yes, the payers of the procedure ( it is not always the patient) must determine if the information from tests is causing the condition of the patient. Everyone must assess the risks, benefits and potential for a positive outcome.
And, unfortunately, these rational decisions must be formulated with a patient is in a lot of pain, with significant frustration, and fear of uncertainly. Sometimes, the severity of the situation may sway the group to make a risky decision that may not be the best one. In the end, it will always come down to a calculated risk. Better clinicians know when to take that risk, and for which circumstance. Better clinicians weigh the information, both scientific and clinical, to make the best decision.
Discussing news and issues in orthopedics and spine healthcare. This is Spine Talk. Hi, this is Dr. John Shim, and today I'm here with Jason Mazza, orthopedic physician assistant. Talking about a very academic topic, but one that's relevant to doctors and radiologists and people who deal with people with back pain. We're going to talk about the issue about the high intensity zone. So, before Jason talks about high intensity zone. We just need to define it. Basically, MRI studies will show areas of inflammation to the various body parts. Radiologists have discovered that there's a small area of inflammation that can be seen at the end of a disc, and that area of inflammation is considered a high intensity zone. Well, the question is what does that actually tell us? Jason? So the study that we looked at comes to us from the Journal of Orthopedic Surgery and Research. The title of the study is Factors associated with lumbar disc HIZ on t2-weighted magnetic resonance imaging. A retrospective study of 3,185 discs in 637 patients. This is a study that comes to us from China. It's a retrospective study where the researchers were looking at MRI images, chart reviews, and post discography images. For over 630 patients. The goal of the study was to clarify the correlation between age, gender, body weight, low back pain, and the presence of an HIZ sign. The results of the study - they found the highest incidence of HIZ lesions occurred in the 50 to 59 years old, and those with the highest body weight. There was a significant difference in the prevalence rates of HIZ lesions, and those that were asymptomatic versus those that were symptomatic. Overall, in the study the prevalence of HIZ was about 31 and a half percent. The author's conclusion, was that the presence of an HIZ lesion on a lumbar MRI was associated with aging, high body weight, and low back symptom. An HIV, excuse me, an H I Z sign indicated part of the natural history of disc degeneration, but is not an actual source of back pain. This goes kind of somewhat against conventional wisdom that all HIZ lesions cause back pain. So, Dr. Shim again in kind of simple terms can you kind of talk more about the HIZ lesion, and kind of what is the relevance of it? Well, so, you know, I was in my training in the early 90's I did my fellowship in 1993. At that time, there was lots of excitements about the use of diagnostic studies - MRIs. And there was a study published by some pretty famous authors where they found these areas of intensity and inflammation on the back of the discs, and they described these things as high intensity zones. And at that time the thought was these high intensity zones identified an acute problem and a source of back pain. So, We're surgeons, we like to fix things. So, we now had a finding. So, we decided, let's operate on these high intensity zones and see how people do. Well, unfortunately, the results weren't very good, and the more we export about high intensity zones - we realized we may not understand it. Initially, the high intensity zones were considered acute findings. In other words, if you find a high intensity zone, it means something happened recently. Well that turned out not to be true because often times if you find these high intensity zones You'll see that same finding for years. So, to say that that means something new happened just doesn't make sense. If you have that same finding it's there for years. It doesn't make sense. There's been follow-up studies that looked at these high intensity zones, and try to identify the correlation of the high intensities zones, or something called an angular tear - a tear of the disc. Well, follow-up studies using CT scans, discograms, and not didn't always match a high intensity zone with the presence of an annular tear. So, unfortunately, this is still a relatively controversial area. To me, its kind of the "we don't know what we don't know" type of scenario again. The thought that it was a source of pain may be true, but we know many instances where these high intensity zones have nothing to do with somebody's pain. So, to me, I don't go by the high intensity zones, simply because I don't know the meaning of that high intensity zone. The other question I have is - obviously we know that that pain and pain perception across different cultural groups varies. Now this was a again a Chinese study. So are there other potentially, biological, maybe morphological or even genetic differences across different cultures that can change or influence at the outcome of a study like this? Well, I mean that's a very broad question, and between you and me, I bet there is something that's genetic and cultural. Because the perception of pain is actually very individual, and it turns out to be also related to your family history, your family reaction to pain, cultural issues with pain, acceptability of pain in certain situations. There are many cultures where people have certain levels of discomfort to their back or their legs or whatnot, but they know there's nothing that can be done about it. So, they just go forward and carry on. They may have these feelings of pain, but it doesn't affect them. There's other cultures where a little bit of pain is really significant, and causes significant disabilities. So, there are cultural issues involved when we're looking at different populations. To me, you know, I look at a lot of studies. You do see studies from different areas of the world. They will say in our population of 3,000 Finnish patients, three thousand Chinese patients, two thousand African patients. They do define their population. Because we're not a hundred percent sure if what happens in the Finnish population is then also going to be correlated or found in the Chinese population. So, to summarize: The high-intensity zone is a finding on MRIs, but still at this time, we do not one hundred percent know what a high-intensity zone means to patients. It may or may not be associated with pain. We hope we didn't confuse you more. This is Dr. Shim and Jason Mazza. Thank you for listening.
Last modified: December 13, 2019