Nomenclature and Classification of Lumbar Disc Pathology

SPINE Volume 26, Number 5, pp E93–E113 ©2001, Lippincott Williams & Wilkins, Inc. Nomenclature and Classification of Lumbar Disc Pathology Recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology David F. Fardon, MD,* and Pierre C. Milette, MD† Preface Introduction Standardization of language is difficult, especially among Physicians need reliable terms that describe normal and those who have expert knowledge of the subject and pathologic conditions of lumbar discs. Terms that can be clear understanding of what their own words mean. The interpreted accurately, consistently, and with reasonable difficulties must be overcome because deleterious effects precision are particularly important for communicating ensue when we do not understand what one another’s impressions gained from imaging for clinical diagnostic words mean. Existing dictionary definitions and previous and therapeutic decision making. Although clear under- efforts by experts have lacked the attention to detail and standing of disc terminology between radiologists and multidisciplinary consensus we brought to this work. clinicians is the focus of this work, such understanding The North American Spine Society (NASS) initiated can be critical, also, to patients, families, employers, in- efforts to develop detailed definitions of lumbar disc pa- surers, jurists, social planners, and researchers. thology terms and has provided sustained support of the In 1995, a multidisciplinary task force from the North project. Independent efforts by neuroradiologists led the American Spine Society (NASS) addressed deficiencies in American Society of Spine Radiology (ASSR) and Amer- standardization and current practice of the language de- ican Society of Neuroradiology (ASNR) to organize a fining conditions of the lumbar disc. It cited several doc- 3–5,13,14,16,28 task force of neuroradiologists and encourage liaison umentations of the problem and made de- with the NASS group. The results are this document and tailed recommendations for standardization. Its work was published in a copublication of NASS and the Amer- improved communications between the societies. 15 The Board of Directors of NASS, and the Executive ican Academy of Orthopedic Surgeons (AAOS). The Committees of both ASSR and ASNR have endorsed this work has not been otherwise endorsed by major organizations and has not been recognized as authoritative document, as has the Joint Section on Disorders of the by radiology organizations. Many previous2,4,13,27– Spine and Peripheral Nerves of the American Association 29,31,33,39,43–45,46,49 and some subsequent12,19,22,24,25,26 of Neurological Surgeons (AANS) and Congress of Neu- efforts have addressed the issues, but have been of more rological Surgeons (CNS), and the CPT and ICD Coding limited scope, and none has gained widespread compli- Committee of the American Academy of Orthopaedic ance or formal endorsement. Surgeons (AAOS). Endorsement by other North Ameri- Although the NASS 1995 effort has been the most can, European, and international societies is currently comprehensive to date, it remains deficient in clarifying pending. This work is being simultaneously posted to the some controversial topics, lacking in its treatment of website of the journal Spine and on the ASSR and ASNR some issues, and does not provide recommendations for websites owing to special arrangements between the ed- standardization of classification and reporting. To ad- itors and publisher of Spine and the American Journal of dress the remaining needs, and in hopes of securing en- Neuroradiology (AJNR). dorsement sufficient to result in universal standardiza- The hope of all of us who have worked on this project tion, joint task forces were formed by NASS, the is that it will ultimately improve the care of patients with American Society of Neuroradiology (ASNR), and the spinal disorders. American Society of Spine Radiology (ASSR). This work David F. Fardon, MD, Chairperson, Clinical Task is the product of those task forces. Force A few general principles guided the generation of this Pierre C. Milette, MD, Chairperson, Imaging Task document. The definitions should be based on the anat- Force omy and pathology. Recognizing that some criteria, under some circumstances, may be unknowable to the ob- server, the definitions of diagnoses should not be dependent on or imply value of specific tests. The defini- *Chairperson, Clinical Task Force. †Chairperson, Imaging Task tions of diagnoses should not define or imply external Force. See the appendix for a complete listing of the members of the Task etiologic events such as trauma. The definitions of diag- Forces and consultants and advisors. noses should not imply relationship to symptoms. Defi- E93 E94 Spine • Volume 26 • Number 5 • 2001 nitions of diagnoses should not define or imply need for Table 1. General Classification of Disc Lesions* specific treatment. ● Normal (excluding aging changes) The task forces worked from a model that could be ● Congenital/developmental variant expanded from a primary purpose of providing under- ● Degenerative/traumatic lesion standing of reports of imaging studies. The result would Anular tear Herniation provide a simple and relatively imprecise classification of Protrusion/extrusion diagnostic terms, based on pathology, which could be Intravertebral expanded, without contradiction, into more precise sub- Degeneration Spondylosis deformans classifications. When reporting pathology, degrees of un- Intervertebral osteochondrosis certainty would be labeled as such rather than compro- ● Inflammation/infection mising on the definitions of the terms. ● Neoplasia ● All terms used in the classifications and subclassifica- Morphologic variant of unknown significance tions were to be defined, and those definitions would be *Adapted with permission from Milette PC. Classification, diagnostic imaging, and imaging characterization of a lumbar herniated disc. Radiol Clin North AM adhered to throughout the model. For practical purpose, 2000;38:1267–1292. some existing English terms were given meanings differ- ent from those found in some contemporary dictionaries. The task forces would provide a list and classification of ing to the information available and purpose to be recommended terms, but, recognizing the nature of lan- served. The data available for categorization may lead guage practices, would discuss, and include in a glossary, the reporter to characterize the interpretation as “possi- commonly used and misused nonrecommended terms ble,” “probable,” or “definite.” and nonstandard definitions. Although the principles and most of the definitions of Normal this document could be easily extrapolated to the cervi- Normal defines young discs that are morphologically cal and dorsal spine, the focus is on the lumbar spine. normal, without consideration of the clinical context and While clarification of terms related to posterior elements not inclusive of degenerative, developmental, or adaptive and disorders related to dimensions of the spinal canal changes that could, in some contexts (e.g., normal aging, are also needed, this work is limited to discussion of the scoliosis, spondylolisthesis) be considered clinically nor- disc. Although it is not always possible to fully discuss mal. However, the bilocular appearance of the adult nu- the definition of anatomic and pathologic terms without cleus resulting from the development of a central hori- some reference to symptoms and etiology, the defini- zontal band of fibrous tissue is considered a sign of tions, themselves, stand the test of independence from normal maturation. etiology, symptoms, or treatment. Because of the focus Congenital/Developmental Variation on anatomy and pathology, this work does not define The Congenital/Developmental Variation category in- certain clinical syndromes that may be related to lumbar cludes discs that are congenitally abnormal or that have disc pathology. undergone changes in their morphology as an adaptation Guided by those principles, this document provides a to abnormal growth of the spine such as from scoliosis or universally acceptable nomenclature that is workable for spondylolisthesis. all forms of observation, that addresses contour, content, integrity, organization, and spatial relationships of the Degenerative/Traumatic lumbar disc; and that serves a system of classification and Degenerative and/or Traumatic changes in the disc are reporting built on that nomenclature. included in a broad category that includes subcategories of Anular Tear; Herniation; and Degeneration. Charac- Recommendations terization of this group of discs as Degenerative/ These recommendations present diagnostic categories Traumatic does not imply that trauma is necessarily a and subcategories, intended for classification and the re- factor or that degenerative changes are necessarily porting of imaging studies. The terminology used pathologic as opposed to the normal aging process. throughout these recommended categories and subcate- Anular tears, also properly called anular fissures, are gories remains consistent with detailed explanations separations between anular fibers, avulsion of fibers given in the Discussion section and with the preferred from their vertebral body insertions, or breaks through definitions presented in the Glossary. fibers that extend radially, transversely, or concentri- The diagnostic categories are based on pathology. cally, involving one or many layers of the anular lamel-

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