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Will That Disc Herniation Get Better? Part II
June 11, 2016 by Dr Matthew D. Long
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Will That Disc Herniation Get Better? Part II
June 11, 2016 by Dr Matthew D. Long
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Will That Disc Herniation Get Better? Part II
June 11, 2016 by Dr Matthew D. Long
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Taking on the role of spinal diagnostician is not easy. Firstly, there is the obvious problem of accurately determining the ‘tissue in lesion’. Our capacity to do this has been debated at length in the literature, with many commentators suggesting that making a tissue diagnosis was simply not possible. After all, our tools for evaluation are plagued by many false positives and negatives. However, in recent years there has been a growing chorus of dissent to this entrenched worldview, and it is becoming accepted that diagnosing the source of spinal pain is indeed practical. I have written about this previously in other blog articles (here, here and here) and it now seems quite safe to say that a well thought out clinical and radiological examination can determine the origin of pain most of the time (1).
Notwithstanding our successes in making a firm diagnosis, we still face an equally important challenge when trying to make a prognosis. Quite simply, how do we know whether a patient is a good candidate for any given treatment, and can we determine how long it will take for them to recover?
In Part I of this topic ("Will That Disc Herniation Get Better?" found here) we looked at the relevance of vertebral endplate changes to those suffering from lumbar disc herniation. In particular, it has been shown that the presence of these Modic changes may suggest that the patient is less likely to recover without surgical intervention. But what about those patients who do not exhibit such dramatic disc herniations? What about those who simply have an annular tear? Can the MRI scan help us to decide whether it is worth pursuing conservative treatment, or should we seriously consider the surgical route?
More recently, an interesting paper by Shan et al (2) has added another small piece to this puzzle of prognosis. The study, entitled "Does the High-Intensity Zone (HIZ) of Lumbar Intervertebral Discs Always Represent an Annular Fissure?" focused upon the MRI appearance of annular tears. For some time now it has been appreciated that an MRI scan is capable of demonstrating fissures within the posterior annulus fibrosus - seen as a bright white spot within the posterior disc wall on a T2-weighted image (which is biased to highlight water concentrations, rather than fat). This High-Intensity Zone (HIZ) is thought to signify the presence of inflammatory fluid or mucoid tissue (3). Indeed, histological studies have shown significant ingrowth of granulation tissue within these fissures, carrying with it both blood vessels and free nerve endings, rendering this pocket highly sensitive (4). This is in stark contrast to the normal annulus, which is composed of a fibrocartilage material that is only minimally innervated and vascularised. While the clinical relevance and reliability of the HIZ was initially debated (because they are also seen in asymptomatic individuals(5)), it has been accepted that a patient with an HIZ and back pain is usually suffering from annular discomfort.
Until now, the key diagnostic clue to the presence of an annular tear was an enhanced signal on the T2 image, signifying the presence of fluid and inflammatory mediators. However, the new paper by Shan and colleagues has further refined this observation by looking at what happens on the T1 image.
Interestingly, we will occasionally see patients who show an obvious high-intensity zone on both the T2 and T1-sequences. This is curious, as the T1 scan does not preferentially highlight water, rather it is attuned to fat concentrations. As such, this observation was thought to be inconsequential, but recent studies now suggest that this may not be the case.
Notwithstanding our successes in making a firm diagnosis, we still face an equally important challenge when trying to make a prognosis. Quite simply, how do we know whether a patient is a good candidate for any given treatment, and can we determine how long it will take for them to recover?
In Part I of this topic ("Will That Disc Herniation Get Better?" found here) we looked at the relevance of vertebral endplate changes to those suffering from lumbar disc herniation. In particular, it has been shown that the presence of these Modic changes may suggest that the patient is less likely to recover without surgical intervention. But what about those patients who do not exhibit such dramatic disc herniations? What about those who simply have an annular tear? Can the MRI scan help us to decide whether it is worth pursuing conservative treatment, or should we seriously consider the surgical route?
More recently, an interesting paper by Shan et al (2) has added another small piece to this puzzle of prognosis. The study, entitled "Does the High-Intensity Zone (HIZ) of Lumbar Intervertebral Discs Always Represent an Annular Fissure?" focused upon the MRI appearance of annular tears. For some time now it has been appreciated that an MRI scan is capable of demonstrating fissures within the posterior annulus fibrosus - seen as a bright white spot within the posterior disc wall on a T2-weighted image (which is biased to highlight water concentrations, rather than fat). This High-Intensity Zone (HIZ) is thought to signify the presence of inflammatory fluid or mucoid tissue (3). Indeed, histological studies have shown significant ingrowth of granulation tissue within these fissures, carrying with it both blood vessels and free nerve endings, rendering this pocket highly sensitive (4). This is in stark contrast to the normal annulus, which is composed of a fibrocartilage material that is only minimally innervated and vascularised. While the clinical relevance and reliability of the HIZ was initially debated (because they are also seen in asymptomatic individuals(5)), it has been accepted that a patient with an HIZ and back pain is usually suffering from annular discomfort.
Until now, the key diagnostic clue to the presence of an annular tear was an enhanced signal on the T2 image, signifying the presence of fluid and inflammatory mediators. However, the new paper by Shan and colleagues has further refined this observation by looking at what happens on the T1 image.
Interestingly, we will occasionally see patients who show an obvious high-intensity zone on both the T2 and T1-sequences. This is curious, as the T1 scan does not preferentially highlight water, rather it is attuned to fat concentrations. As such, this observation was thought to be inconsequential, but recent studies now suggest that this may not be the case.
Figure 1. MRI images of high-intensity zones (HIZ). Single-HIZ disc: HIZ on a sagittal T2- weighted MR image (a) compared to an isointense zone on a T1-weighted MR image (b). Dual-HIZ disc: a high intensity zone on both sagittal T2- (c) and T1-weighted (d) MR images. From Shan et al.
In Shan’s study they collected samples from the posterior annulus of patients undergoing disc surgery. While investigating the constituents of the annular fissure, they found that those with a high T1 reading contained more calcium, silicon and phosphorous. Indeed, it appears that these individuals exhibited annular fissures containing fragments of bone of calcified cartilage. Furthermore, these lesions contained fewer blood vessels and macrophages, suggesting that the tear was not a typical annular injury. The authors concluded that it probably represented an avulsion of the endplate, occurring as the annulus pulled a fragment of bone away during the injury.
Shan’s paper concluded that,
“In summary, we conclude that an HIZ on both T2 and T1-weighted images might represent fragments of the bony endplate and/or calcification of the posterior annulus fibrosus of the targeted discs. In contrast, an HIZ on T2-weighted images only most likely represents an annular fissure combined with granulation in-growth. From this viewpoint, the conventional concept of an HIZ should be modified to encompass both single HIZ and dual HIZs.”
Interestingly, the authors also observed that,
“Finally, one clinical application of these results is that conservative treatments are less likely to be effective for patients with dual HIZs, and surgical treatments are more often suggested.”
So patients exhibiting a 'dual HIZ' (both T2 and T1-weighted images) are less likely to improve without surgery. This seems logical when we take into account the established literature on the natural history and resolution of disc herniation. Quite simply, when the protruding material is composed mostly of nucleus pulposus there is a greater capacity for the material to shrink over time. This is due to the fact that the main constituent of nuclear material is proteoglycan aggrecans, an extremely hydrophilic substance that binds many times its own weight in water. As time passes, the macrophages in the epidural space will denature the material, causing it to dehydrate and shrink (6). However, those protrusions that have a mixed composition (including cartilage, bone and ligament) appear to have far less capacity to resorb and shrink over time, often requiring surgical intervention. It also seems that the annular tears might also need to be managed this way.
To summarise, those individuals who demonstrate an HIZ only on the T2-weighted images are most likely exhibiting shorter-term pain, due to an inflammatory lesion within their annulus. However, those who exhibit a high signal on both the T1 and T2 sequences may well have a poorer outlook, as the lesion probably contains cartilage and bone fragments, reducing the chance for spontaneous resolution.
Something to think about anyway...
Dr Matthew D. Long
BSc (Syd) M.Chiro (Macq)
To summarise, those individuals who demonstrate an HIZ only on the T2-weighted images are most likely exhibiting shorter-term pain, due to an inflammatory lesion within their annulus. However, those who exhibit a high signal on both the T1 and T2 sequences may well have a poorer outlook, as the lesion probably contains cartilage and bone fragments, reducing the chance for spontaneous resolution.
Something to think about anyway...
Dr Matthew D. Long
BSc (Syd) M.Chiro (Macq)
References:
1. DePalma, M. J. (2015). Diagnostic Nihilism Toward Low Back Pain: What Once Was Accepted, Should No Longer Be. Pain Medicine (Malden, Mass), n/a–n/a. http://doi.org/10.1111/pme.12850
2. Shan, Z., Chen, H., Liu, J., Ren, H., Zhang, X., & Zhao, F. (2016). Does the high-intensity zone (HIZ) of lumbar Intervertebral discs always represent an annular fissure? European Radiology, 1–10. http://doi.org/10.1007/s00330-016-4408-1
3. Peng, B., Hou, S., Wu, W., Zhang, C., & Yang, Y. (2006). The pathogenesis and clinical significance of a high-intensity zone (HIZ) of lumbar intervertebral disc on MR imaging in the patient with discogenic low back pain. European Spine Journal, 15(5), 583–587. http://doi.org/10.1007/s00586-005-0892-8
4. Stefanakis, M., Al-Abbasi, M., Harding, I., Pollintine, P., Dolan, P., Tarlton, J., & Adams, M. A. (2012). Annulus fissures are mechanically and chemically conducive to the ingrowth of nerves and blood vessels. Spine, 37(22), 1883–1891. http://doi.org/10.1097/BRS.0b013e318263ba59
5. Carragee E, Paragioudakis SJ, Khurana S (2000) Lumbar high-intensity zone and discography in subjects without low back problems. Spine 25:2987–2992
6. Cribb, G. L., Jaffray, D. C., & Cassar-Pullicino, V. N. (2007). Observations on the natural history of massive lumbar disc herniation. The Journal of Bone and Joint Surgery British Volume, 89(6), 782–784. doi:10.1302/0301-620X.89B6.18712
1. DePalma, M. J. (2015). Diagnostic Nihilism Toward Low Back Pain: What Once Was Accepted, Should No Longer Be. Pain Medicine (Malden, Mass), n/a–n/a. http://doi.org/10.1111/pme.12850
2. Shan, Z., Chen, H., Liu, J., Ren, H., Zhang, X., & Zhao, F. (2016). Does the high-intensity zone (HIZ) of lumbar Intervertebral discs always represent an annular fissure? European Radiology, 1–10. http://doi.org/10.1007/s00330-016-4408-1
3. Peng, B., Hou, S., Wu, W., Zhang, C., & Yang, Y. (2006). The pathogenesis and clinical significance of a high-intensity zone (HIZ) of lumbar intervertebral disc on MR imaging in the patient with discogenic low back pain. European Spine Journal, 15(5), 583–587. http://doi.org/10.1007/s00586-005-0892-8
4. Stefanakis, M., Al-Abbasi, M., Harding, I., Pollintine, P., Dolan, P., Tarlton, J., & Adams, M. A. (2012). Annulus fissures are mechanically and chemically conducive to the ingrowth of nerves and blood vessels. Spine, 37(22), 1883–1891. http://doi.org/10.1097/BRS.0b013e318263ba59
5. Carragee E, Paragioudakis SJ, Khurana S (2000) Lumbar high-intensity zone and discography in subjects without low back problems. Spine 25:2987–2992
6. Cribb, G. L., Jaffray, D. C., & Cassar-Pullicino, V. N. (2007). Observations on the natural history of massive lumbar disc herniation. The Journal of Bone and Joint Surgery British Volume, 89(6), 782–784. doi:10.1302/0301-620X.89B6.18712