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Further doubt is cast on the significance of the high intensity zone
Clinical Radiology (2004) 59, 1000–1001
COMMENTARY
Further doubt is cast on the significance of the high intensity zone J.J. Rankine Department of Radiology, St James University Hospital Leeds, Leeds, UK
When the high intensity zone (HIZ) was first described in 1992,1 many hoped that that we had seen the end of discography as an invasive test for symptomatic disc degeneration. The fact that discography is still practised in many centres, 12 years later, tells us that our hopes were not realised. The demonstration that stress discography can induce a pain response in entirely asymptomatic individuals2 questions its role as a gold standard for testing the significance of the HIZ. The true gold standard for the HIZ is how it relates to a patient’s symptoms, and what happens to it and the patient’s symptoms over time. The paper by Mitra et al.3 is very important since it is the first investigation to address the natural history of the HIZ. On follow-up magnetic resonance imaging, Mitra and colleagues found that some HIZs remained unchanged, some got worse, some better and some resolved altogether. Retrospective recruitment of patients for the study hampered the initial clinical assessment, but within these limitations they have made valid attempts to correlate changing symptoms over time with changing appearances of the demonstrated HIZ. The fact that they were unable to show a correlation is perhaps not surprising when one considers the poor correlation between degenerative changes and symptoms, and the high prevalence of such changes in asymptomatic individuals. What then is the HIZ, and is it just another feature of degeneration? Terminology is confusing with terms ‘HIZ’, ‘annular fissure’ and ‘annular tear’ all being applied to the same abnormality. The term HIZ is a cumbersome description of an MRI appearance, and unfortunately the use of this term has
E-mail address: [email protected] 0009-9260/$ - see front matter doi:10.1016/j.crad.2004.06.002
stuck, appearing in various papers since the original description. Before this, discography was widely used to demonstrate annular fissures, and there seems little doubt that the HIZ is a form of annular fissure. The term annular tear is used synonymously with HIZ, but is unfortunate, since it implies a traumatic aetiology whereas there is no evidence in the literature that HIZs are related to individual episodes of trauma. That there is a large number of cases currently going through the courts, of individuals claiming compensation for injuries on the basis of an annular tear, points to the dangers of using this term. Annular fissure then is the most appropriate term, since it implies a degenerative aetiology. Before this study by Mitra et al., we had no real knowledge of what happened to the HIZ over time. The real interest of their current paper is that the appearance of the HIZ, and subsequent resolution, may represent a stage in the degenerative process of the disc. That some HIZs worsened, and some resolved, could represent different stages in the evolution in different patients. It would be interesting to know if there were any correlation between the appearance of the nucleus pulposus and the changing appearances of the HIZ. One might expect worsening appearances of the HIZ to occur in relatively well hydrated discs, and resolution to occur in discs with poor hydration, if the HIZ represents a stage in the progression of degeneration. The authors might consider further analysis of their data to investigate this. The HIZ is then part and parcel of the degenerative process of some discs. We should interpret the significance of the HIZ with the same caution that we apply to other features of degeneration on MRI.
Further doubt is cast on the significance of the high intensity zone
References 1. Aprill C, Bogduk N. High-intensity zone: a diagnostic sign of painful lumbar disc on magnetic resonance imaging. Br J Radiol 1992;65:361—9. 2. Carragee E, Paragioudakis S, Khurana S. Lumbar high-intensity
1001
zone and discography in subjects without low back problems. Spine 2000;25:2987—92. 3. Mitra D, Cassar-Pullicino VN, McCall IW. Longitudinal study of high intensity zones on MR on lumbar intervertebral discs. Clin Radiol 2004;59:1002—8.
COMMENTARY
Further doubt is cast on the significance of the high intensity zone J.J. Rankine Department of Radiology, St James University Hospital Leeds, Leeds, UK
When the high intensity zone (HIZ) was first described in 1992,1 many hoped that that we had seen the end of discography as an invasive test for symptomatic disc degeneration. The fact that discography is still practised in many centres, 12 years later, tells us that our hopes were not realised. The demonstration that stress discography can induce a pain response in entirely asymptomatic individuals2 questions its role as a gold standard for testing the significance of the HIZ. The true gold standard for the HIZ is how it relates to a patient’s symptoms, and what happens to it and the patient’s symptoms over time. The paper by Mitra et al.3 is very important since it is the first investigation to address the natural history of the HIZ. On follow-up magnetic resonance imaging, Mitra and colleagues found that some HIZs remained unchanged, some got worse, some better and some resolved altogether. Retrospective recruitment of patients for the study hampered the initial clinical assessment, but within these limitations they have made valid attempts to correlate changing symptoms over time with changing appearances of the demonstrated HIZ. The fact that they were unable to show a correlation is perhaps not surprising when one considers the poor correlation between degenerative changes and symptoms, and the high prevalence of such changes in asymptomatic individuals. What then is the HIZ, and is it just another feature of degeneration? Terminology is confusing with terms ‘HIZ’, ‘annular fissure’ and ‘annular tear’ all being applied to the same abnormality. The term HIZ is a cumbersome description of an MRI appearance, and unfortunately the use of this term has
E-mail address: [email protected] 0009-9260/$ - see front matter doi:10.1016/j.crad.2004.06.002
stuck, appearing in various papers since the original description. Before this, discography was widely used to demonstrate annular fissures, and there seems little doubt that the HIZ is a form of annular fissure. The term annular tear is used synonymously with HIZ, but is unfortunate, since it implies a traumatic aetiology whereas there is no evidence in the literature that HIZs are related to individual episodes of trauma. That there is a large number of cases currently going through the courts, of individuals claiming compensation for injuries on the basis of an annular tear, points to the dangers of using this term. Annular fissure then is the most appropriate term, since it implies a degenerative aetiology. Before this study by Mitra et al., we had no real knowledge of what happened to the HIZ over time. The real interest of their current paper is that the appearance of the HIZ, and subsequent resolution, may represent a stage in the degenerative process of the disc. That some HIZs worsened, and some resolved, could represent different stages in the evolution in different patients. It would be interesting to know if there were any correlation between the appearance of the nucleus pulposus and the changing appearances of the HIZ. One might expect worsening appearances of the HIZ to occur in relatively well hydrated discs, and resolution to occur in discs with poor hydration, if the HIZ represents a stage in the progression of degeneration. The authors might consider further analysis of their data to investigate this. The HIZ is then part and parcel of the degenerative process of some discs. We should interpret the significance of the HIZ with the same caution that we apply to other features of degeneration on MRI.
Further doubt is cast on the significance of the high intensity zone
References 1. Aprill C, Bogduk N. High-intensity zone: a diagnostic sign of painful lumbar disc on magnetic resonance imaging. Br J Radiol 1992;65:361—9. 2. Carragee E, Paragioudakis S, Khurana S. Lumbar high-intensity
1001
zone and discography in subjects without low back problems. Spine 2000;25:2987—92. 3. Mitra D, Cassar-Pullicino VN, McCall IW. Longitudinal study of high intensity zones on MR on lumbar intervertebral discs. Clin Radiol 2004;59:1002—8.