SPINE Volume 26, Number 5, pp E93 3E113 ©2001, Lippincott Williams & Wilkins, Inc. Nomenclature and Classi2cation 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 StandardizationoflanguageisdifNcult,especiallyamong those who have expert knowledge of the subject and clear understanding of what their own words mean. The difNculties must be overcome because deleterious effects ensue when we do not understand what one another 9s words mean. Existing dictionary deNnitions and previous efforts by experts have lacked the attention to detail and multidisciplinary consensus we brought to this work.
The North American Spine Society (NASS) initiated efforts to develop detailed deNnitions of lumbar disc pa- thology terms and has provided sustained support of the project. Independent efforts by neuroradiologists led the American Society of Spine Radiology (ASSR) and Amer- ican Society of Neuroradiology (ASNR) to organize a task force of neuroradiologists and encourage liaison with the NASS group. The results are this document and improved communications between the societies.
The Board of Directors of NASS, and the Executive CommitteesofbothASSRandASNRhaveendorsedthis document, as has the Joint Section on Disorders of the ... more. less.
SpineandPeripheralNervesoftheAmericanAssociation of Neurological Surgeons (AANS) and Congress of Neu- rological Surgeons (CNS), and the CPT and ICD Coding Committee of the American Academy of Orthopaedic Surgeons (AAOS). Endorsement by other North Ameri- can, European, and international societies is currently pending.Thisworkisbeingsimultaneouslypostedtothe website of the journal Spine and on the ASSR and ASNR websites owing to special arrangements between the ed- itors and publisher of Spine and the American Journalof Neuroradiology (AJNR). Thehopeofallofuswhohaveworkedonthisproject isthatitwillultimatelyimprovethecareofpatientswith spinal disorders.<br><br> David F. Fardon, MD, Chairperson, Clinical Task Force Pierre C. Milette, MD, Chairperson, Imaging Task Force Introduction Physicians need reliable terms that describe normal and pathologicconditionsoflumbardiscs.Termsthatcanbe interpreted accurately, consistently, and with reasonable precision are particularly important for communicating impressions gained from imaging for clinical diagnostic and therapeutic decision making.<br><br> Although clear under- standing of disc terminology between radiologists and clinicians is the focus of this work, such understanding can be critical, also, to patients, families, employers, in- surers, jurists, social planners, and researchers. In1995,amultidisciplinarytaskforcefromtheNorth American Spine Society (NASS) addressed deNciencies in standardization and current practice of the language de- Nning conditions of the lumbar disc. It cited several doc- umentations of the problem 3 35,13,14,16,28 and made de- tailed recommendations for standardization.<br><br> Its work waspublishedinacopublicationofNASSandtheAmer- ican Academy of Orthopedic Surgeons (AAOS). 15 The work has not been otherwise endorsed by major organi- zations and has not been recognized as authoritative by radiology organizations. Many previous 2,4,13,27 3 29,31,33,39,43 345,46,49 and some subsequent 12,19,22,24,25,26 efforts have addressed the issues, but have been of more limited scope, and none has gained widespread compli- ance or formal endorsement.<br><br> Although the NASS 1995 effort has been the most comprehensive to date, it remains deNcient in clarifying some controversial topics, lacking in its treatment of some issues, and does not provide recommendations for standardization of classiNcation and reporting. To ad- dress the remaining needs, and in hopes of securing en- dorsement sufNcient to result in universal standardiza- tion, joint task forces were formed by NASS, the American Society of Neuroradiology (ASNR), and the American Society of Spine Radiology (ASSR). This work is the product of those task forces.<br><br> A few general principles guided the generation of this document. The deNnitions should be based on the anat- omy and pathology. Recognizing that some criteria, un- der some circumstances, may be unknowable to the ob- server, the deNnitions of diagnoses should not be dependent on or imply value of speciNc tests.<br><br> The deNni- tions of diagnoses should not deNne or imply external etiologic events such as trauma. The deNnitions of diag- noses should not imply relationship to symptoms. DeN- *Chairperson, Clinical Task Force.<br><br> Chairperson, Imaging Task Force. See the appendix for a complete listing of the members of the Task Forces and consultants and advisors. E93 nitions of diagnoses should not deNne or imply need for speciNc treatment.<br><br> The task forces worked from a model that could be expanded from a primary purpose of providing under- standing of reports of imaging studies. The result would provideasimpleandrelativelyimpreciseclassiNcationof diagnostic terms, based on pathology, which could be expanded, without contradiction, into more precise sub- classiNcations.Whenreportingpathology,degreesofun- certainty would be labeled as such rather than compro- mising on the deNnitions of the terms. All terms used in the classiNcations and subclassiNca- tions were to be deNned, and those deNnitions would be adhered to throughout the model.<br><br> For practical purpose, some existing English terms were given meanings differ- entfromthosefoundinsomecontemporarydictionaries. The task forces would provide a list and classiNcation of recommended terms, but, recognizing the nature of lan- guagepractices,woulddiscuss,andincludeinaglossary, commonly used and misused nonrecommended terms and nonstandard deNnitions. Although the principles and most of the deNnitions of this document could be easily extrapolated to the cervi- cal and dorsal spine, the focus is on the lumbar spine.<br><br> While clariNcation of terms related to posterior elements and disorders related to dimensions of the spinal canal are also needed, this work is limited to discussion of the disc. Although it is not always possible to fully discuss the deNnition of anatomic and pathologic terms without some reference to symptoms and etiology, the deNni- tions, themselves, stand the test of independence from etiology, symptoms, or treatment. Because of the focus on anatomy and pathology, this work does not deNne certain clinical syndromes that may be related to lumbar disc pathology.<br><br> Guided by those principles, this document provides a universallyacceptablenomenclaturethatisworkablefor allformsofobservation,thataddressescontour,content, integrity, organization, and spatial relationships of the lumbardisc;andthatservesasystemofclassiNcationand reporting built on that nomenclature. Recommendations These recommendations present diagnostic categories and subcategories, intended for classiNcation and the re- porting of imaging studies. The terminology used throughout these recommended categories and subcate- gories remains consistent with detailed explanations given in the Discussion section and with the preferred deNnitions presented in the Glossary.<br><br> The diagnostic categories are based on pathology. Each lumbar disc can be classiNed in terms of one, and occasionally more than one, of the following diagnostic categories: Normal; Congenital/Developmental Varia- tion; Degenerative/Traumatic; Infectious/InOammatory; Neoplastic; and/or Morphologic Variant of Uncertain SigniNcance (Table 1). Each diagnostic category can be subcategorized to various degrees of speciNcity accord- ing to the information available and purpose to be served.<br><br> The data available for categorization may lead the reporter to characterize the interpretation as cpossi- ble, d cprobable, d or cdeNnite. d Normal Normal deNnes young discs that are morphologically normal,withoutconsiderationoftheclinicalcontextand notinclusiveofdegenerative,developmental,oradaptive changesthatcould,insomecontexts( e.g. ,normalaging, scoliosis, spondylolisthesis) be considered clinically nor- mal. However, the bilocular appearance of the adult nu- cleus resulting from the development of a central hori- zontal band of Nbrous tissue is considered a sign of normal maturation.<br><br> Congenital/Developmental Variation The Congenital/Developmental Variation category in- cludes discs that are congenitally abnormal or that have undergonechangesintheirmorphologyasanadaptation toabnormalgrowthofthespinesuchasfromscoliosisor spondylolisthesis. Degenerative/Traumatic Degenerative and/or Traumatic changes in the disc are included in a broad category that includes subcategories of Anular Tear; Herniation; and Degeneration. Charac- terization of this group of discs as Degenerative/ Traumatic does not imply that trauma is necessarily a factor or that degenerative changes are necessarily pathologic as opposed to the normal aging process.<br><br> Anular tears , also properly called anular 2ssures , are separations between anular Nbers, avulsion of Nbers from their vertebral body insertions, or breaks through Nbers that extend radially, transversely, or concentri- cally, involving one or many layers of the anular lamel- lae. The terms ctear d or cNssure d describe the spectrum of such lesions and do not imply that the lesion is conse- quent to trauma (Figure 1). Degeneration may include any or all of real or appar- ent desiccation, Nbrosis, narrowing of the disc space, diffuse bulging of the anulus beyond the disc space, ex- tensive Nssuring ( i.e.<br><br> , numerous anular tears), and muci- Table 1. General Classification of Disc Lesions* Ï Normal (excluding aging changes) Ï Congenital/developmental variant Ï Degenerative/traumatic lesion Anular tear Herniation Protrusion/extrusion Intravertebral Degeneration Spondylosis deformans Intervertebral osteochondrosis Ï InBammation/infection Ï Neoplasia Ï Morphologic variant of unknown signiAcance *Adapted with permission from Milette PC. Classi'cation, diagnostic imaging, and imaging characterization of a lumbar herniated disc.<br><br> Radiol Clin North AM 2000;38:1267 31292. E94 Spine " Volume 26 " Number 5 " 2001 nous degeneration of the anulus, defects and sclerosis of the endplates, and osteophytes at the vertebral apophy- ses. A disc demonstrating one or more of these degener- ative changes can be further qualiNed into two subcate- gories: spondylosis deformans , possibly representing changesinthediscassociatedwithanormalagingprocess; or intervertebral osteochondrosis , possibly the conse- quences of a more clearly pathologic process (Figure 2) .<br><br> Herniation is deNned as a localized displacement of disc material beyond the limits of the intervertebral disc space (Figure 1). The disc material may be nucleus, car- tilage,fragmentedapophysealbone,anulartissue,orany combination thereof. The disc space is deNned, craniad and caudad, by the vertebral body endplates (Figure 3) and,peripherally,bytheouteredgesofthevertebralring apophyses, exclusive of osteophytic formations (Figure 4).<br><br> The term clocalized d contrasts to cgeneralized, d the latter being arbitrarily deNned as greater than 50% (180 degrees) of the periphery of the disc (Figure 5). Localized displacement in the axial (horizontal) plane can be cfocal, d signifying less than 25% of the disc cir- cumference (Figure 6), or cbroad-based, d meaning be- tween 25 and 50% of the disc circumference (Figure 7). Presence of disc tissue ccircumferentially d (50 3100%) beyond the edges of the ring apophyses may be called cbulging d and is not considered a form of herniation (Figure 8), nor are diffuse adaptive alterations of disc Figure 1.<br><br> Schematic sagittal anatomic sections showing the dif- ferentiating features of an anular tear (radial tear in this case) and a disc herniation. The term ctear d is used to refer to a localized radial, concentric, or horizontal disruption of the anulus without associated displacement of disc material beyond the limits of the intervertebral disc space. Nuclear material is shown in black, and the anulus (internal and external) corresponds to the white portion of the intervertebral space.<br><br> The same convention is used in Fig- ures 2, 11, 12, and 13. (Adapted with permission from Milette PC. The proper terminology for reporting lumbar intervertebral disk disorders.<br><br> AJNR Am J Neuroradiol 1997; 18: 1859 31866.) Figure 2. Schematic sagittal anatomic sections showing the dif- ferentiating characteristics of the normal disc, spondylosis defor- mans, and intervertebral osteochondrosis. The distinction be- tween these three entities is usually possible on all imaging modalities, including conventional radiographs.<br><br> (Adapted with permission. 25 ) Figure 3. The term cherniated disc, d as deAned in this work, refers to localized displacement of nucleus, cartilage, fragmented ap- ophyseal bone, or fragmented anular tissue beyond the interver- tebral disc space (disc space, interspace).<br><br> The interspace is deAned, craniad and caudad, by the vertebral body endplates. Two intravertebral herniations, one with an upward orientation and the other with a downward orientation with respect to the disc space, are illustrated schematically. Figure 4.<br><br> The interspace is deAned, peripherally, by the edges of the vertebral ring apophyses, exclusive of osteophytic formations. The line drawing schematically illustrates a localized extension of disc material beyond the intervertebral disc space, in a left pos- terior direction, which qualiAes as a disc herniation. E95 Lumbar Disc Pathology: Recommendations " North American Spine Society et al contour secondary to adjacent deformity as may be presentinseverescoliosisorspondylolisthesis(Figure9).<br><br> Herniated discs may take the form of protrusion or extrusion, based on the shape of the displaced material (Figure 10). Protrusion is present if the greatest distance, in any plane, between the edges of the disc material be- yond the disc space is less than the distance between the edges of the base, in the same plane. The base is deNned as the cross-sectional area of disc material at the outer margin of the disc space of origin, where disc material displaced beyond the disc space is continuous with disc material within the disc space.<br><br> In the cranio-caudal di- rection, the length of the base cannot exceed, by deNni- tion, the height of the intervertebral space. Extrusion is present when, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base, or when no continuity exists between the disc material beyond the disc space and that within the disc space (Figure 11). Extrusion may be further speciNed as sequestration, ifthedisplaceddiscmaterialhaslostcom- pletely any continuity with the parent disc (Figure 12).<br><br> The term migration may be used to signify displacement of disc material away from the site of extrusion, regard- less of whether sequestrated or not (Figure 13). Because posteriorly displaced disc material is often constrained by the posterior longitudinal ligament, images may por- trayadiscdisplacementasaprotrusiononaxialsections Figure 5. For classiAcation purposes, the intervertebral disc is con- sidered as a two-dimensional round or oval structure having four 90° quadrants.<br><br> By convention, a herniation is a clocalized d process in- volving less than 50% (180°) of the disc circumference. Figure 6. By convention, a cfocal herniation d involves less than 25% (90°) of the disc circumference.<br><br> Figure 7. By convention, a cbroad-based d herniation involves be- tween 25% and 50% (90 3180°) of the disc circumference. Figure 8.<br><br> Symmetrical presence (or apparent presence) of disc tissue ccircumferentially d (50 3100%) beyond the edges of the ring apophyses may be described as a cbulging disc d or cbulging appearance d and is not considered a form of herniation. Further- more, cbulging d is a descriptive term for the shape of the disc contour and not a diagnostic category. E96 Spine " Volume 26 " Number 5 " 2001 and an extrusion on sagittal sections, in which cases the displacement should be considered an extrusion.<br><br> Herni- ated discs in the cranio-caudal (vertical) direction through a break in the vertebral body endplate are re- ferred to as intravertebral herniations . Disc herniations may be further speciNcally described as contained , if the displaced portion is covered by outer anulus, or uncontained when absent any such covering. Displaced disc tissues may also be described by location, volume,andcontent,asdiscussedlaterinthisdocument.<br><br> Table 2 lists the proposed categories for description and classiNcation of disc herniations. Inflammation/Infection The category of InOammation/ Infection includes infection, infection-like inOammatory discitis, and inOammatory response to spondyloar- thropathy. It also includes inOammatory spondylitis of subchondral endplate and bone marrow manifested as Modic Type 1 magnetic resonance imaging (MRI) changes and usually associated with pathologic changes in the disc.<br><br> To simplify the classiNcation scheme, the category is inclusive of disparate conditions; therefore, when data permit, the diagnosis should be subcatego- rized for appropriate speciNcity. Neoplasia Primary or metastatic morphologic changes of disc tis- sues caused by neoplasia are categorized as Neoplasia, with subcategorization for appropriate speciNcity. Figure 9.<br><br> Asymmetrical bulging of the disc margin (50 3100%), such as what is found in severe scoliosis, is also not considered a form of herniation. Figure 10. Herniated discs may take the form of protrusion or extrusion, based on the shape of the displaced material (see deAnitions in text).<br><br> Figure 11. When a relatively large amount of disc material is displaced, distinction between protrusion (A) and extrusion (B or C) will generally only be possible on sagittal magnetic resonance (MR) sections or sagittal computed tomography (CT) reconstruc- tions. C , Although the shape of the displaced material is similar to that of a protrusion, the greatest cranio-caudal diameter of the fragment is greater than the cranio-caudal diameter of its base at the level of the parent disc, and the lesion therefore qualiAes as an extrusion.<br><br> In any situation, the distance between the edges of the base, which serves as reference for the deAnition of protrusion and extrusion, may differ from the distance between the edges of the aperture of the anulus, which cannot be assessed on CT images and is seldom appreciated on MR images. In the cranio- caudal direction, the length of the base cannot exceed, by deA- nition, the height of the intervertebral space. (Reprinted with permission from Milette PC.<br><br> ClassiAcation, diagnostic imaging and imaging characterization of a lumbar herniated disc. Radiol Clin North Am 2000; 38:1267 31292.) Figure 12. Schematic representation of various types of posterior central herniations.<br><br> A, Small subligamentous herniation (or protru- sion) without signiAcant disc material migration. B, Subligamen- tous herniation with downward migration of disc material under the posterior longitudinal ligament (PLL). C, Subligamentous her- niation with downward migration of disc material and sequestered fragment (arrow).<br><br> (Reprinted with permission from Milette PC. ClassiAcation, diagnostic imaging and imaging characterization of a lumbar herniated disc. Radiol Clin North Am 2000; 38:1267 31292.) E97 Lumbar Disc Pathology: Recommendations " North American Spine Society et al Morphologic Variant of Unknown Significance Instancesinwhichdatasuggestabnormalmorphologyof the disc but are not complete enough to warrant a diag- nostic categorization can be categorized as Morphologic Variant of Unknown SigniNcance.<br><br> Discussion Acceptance and standardization occur most easily when recommendations are close to common practice. How- ever, there are many contradictory views of common practice and some common practices are contradictory to our primary purpose, which is clear communication betweenthosewhointerpretimagesandthosewhomake clinical decisions. This document deNnes a nomenclature that describes discs and leaves to the clinician the description of the patient.<br><br> In so doing, however, this provides a nomencla- ture that facilitates description of surgical or endoscopic Nndings as well as images; and also, with the caveat that itaddressesonlythemorphologyofthedisc,itfacilitates communication for patients, families, employers, insur- ers, and legal and social authorities, and permits accu- mulation of more reliable data for research. Normal Categorization of a disc as cNormal d means the disc is fully and normally developed and free of any changes of disease,trauma,oraging.Onlythemorphology,andnot the clinical context, is considered. In common practice, people with a variety of harmless congenital or develop- mental variations of discs, minor bulging of anuli, ante- riorandlateralmarginalvertebralbodyosteophytes, etc.<br><br> are normal people. By this nomenclature and classiNca- tion, however, such individual discs are not considered cnormal. d Therein lies a signiNcant difference of this method from what many would consider common prac- tice. Some people are clinically cnormal d even though they have morphologically abnormal discs.<br><br> Anular Tears/Fissures There is general agreement about the various forms of loss of integrity of the anulus, such as radial, transverse, and concentric separations. Some, including the 1995 NASS document, 15 have recommended that such lesions be termed cNssures d rather than ctears, d primarily for fear that the word ctear d could be misconstrued as im- plying a traumatic etiology. Common practice, as docu- mented by review of contemporary specialty journal lit- erature 12 shows preference, among authors of various disciplines, for the term ctear, d and frequent synony- mous use in the same articles of the terms ctear d and cNssure. d Inthisinstance,itisunwisetorecommendcontraryto ingrained common usage but wise to reiterate the caveat that the term canular tear d does not imply traumatic etiology.<br><br> In the case where a single, traumatic event is clearlythesourceoflossofintegrityofaformallynormal anulus, such as with documentation and Nndings of vio- lent distraction injury, the term crupture d of the anulus is appropriate, but use of the term crupture d as synony- mous with commonly observed tears or Nssures is con- traindicated. In conclusion, therefore, canular tear d and canular Nssure d are both acceptable terms, can be used properlyassynonyms,anddonotimplythatasigniNcant traumatic event has occurred or that the etiology is known. Some tears may have clinical relevance and others may be asymptomatic and inconsequential components of the aging process.<br><br> Correlation of the characteristics of the tear with responses to discography and other clini- cally relevant observations may enable the observer to make such distinctions, but such is beyond the scope of this morphologically based deNnition and classiNcation model. Figure 13. Relationship of typical posterior disc herniations with the posterior longitudinal ligament.<br><br> A, Midline sagittal section: Unless very large, a posterior midline herniation usually remains entrapped underneath the deep layer of the PLL and sometimes a few intact outer anulus Abers joining with the PLL to form a ccapsule. d The deep layer of the PLL (arrow) also attaches to the posterior aspect of the vertebral body so that no potential space is present underneath. B, Sagittal para-central section: The PLL extends laterally at the disc level (arrowhead) but, above and below the disc, an anterior epidural space (as), where disc frag- ments are frequently entrapped, is present between the lateral (peridural) membranes and the posterior aspect of the vertebral bodies. (Adapted with permission from Milette PC.<br><br> ClassiAcation, diagnostic imaging and imaging characterization of a lumbar her- niated disc. Radiol Clin North Am 2000;38:1267 31292.) Table 2. Description of a Disc Herniation " Morphology Protrusion Extrusion Intravertebral " Containment " Continuity " Relation with PLL complex " Volume " Composition " Location E98 Spine " Volume 26 " Number 5 " 2001 Disc Degeneration Becausethereisconfusionindifferentiationofchangesof pathologic degenerative processes in the disc from those of normal aging, 8,30,38 the classiNcation category cDe- generative/Traumatic d includes all such changes, thus does not compel the observer to differentiate the patho- logic from the normal consequences of aging.<br><br> However, this model allows the observer with adequate data to present a more enlightening report by making such a distinction, with appropriate notation of the degree of conNdence. Perceptions of what constitutes the normal aging pro- cess of the spine have been greatly inOuenced by postmor- tem anatomic studies involving a limited number of speci- mens, harvested from cadavers from different age groups, with unknown past medical histories, and the presump- tion of absence of lumbar symptoms. 7,9,17,20,23,34 With such methods, pathologic changes are easily confused with consequences of normal aging.<br><br> Resnick and Ni- wayama 35 emphasizedthedifferentiatingfeaturesoftwo degenerative processes involving the intervertebral disc, which had been previously described by Schmorl and Junghanns 37 : cspondylosisdeformans, dwhichaffectses- sentiallytheanulusNbrosusandadjacentapophyses,and cintervertebral osteochondrosis, d which affects mainly the nucleus pulposus and the vertebral body endplates, but also includes extensive Nssuring (numerous tears) of the anulus Nbrosus, which may be followed by atrophy (Figure 2). Although Resnick and Niwayama stated that the cause of the two entities was unknown, other scien- tiNc studies suggest that spondylosis deformans is the consequence of normal aging, whereas intervertebral os- teochondrosis, sometimes also called cdeteriorated disc, d results from a clearly pathologic, although not necessarily symptomatic, process. 32,36,37,40,41 With normal aging, Nbrous tissue replaces nuclear mucoid matrix, but the disc height is preserved and the disc margins remain regular.<br><br> 22 Radial tears of the anulus are found only in a minority of postmortem examina- tions of individuals over 40 years of age, 23 so cannot be considered a usual consequence of aging. Slight symmet- ric bulging of the disc may occur in the elderly remodel- ing associated with osteoporosis. 41 On conventional ra- diographs and computed tomography (CT), small amounts of gas can be detected in some elderly individ- uals at the anular/apophyseal enthesis, probably located in small transverse anular tears, and possibly signifying early manifestations of spondylosis deformans 49 ; how- ever, a large amount of gas in the central disc space is always pathologic and is a feature of intervertebral os- teochondrosis.<br><br> 35 Anterior and lateral marginal vertebral body osteophytes have been found in 100% of skeletons of individuals over 40, so are consequences of normal aging, whereas posterior osteophytes have been found in onlyaminorityofskeletonsofindividualsover80,soare not inevitable consequences of aging. 32 Endplate ero- sions with osteosclerosis and chronic reactive bone mar- rowchangesalsoappeartobepathologic.Slighttomod- erate decrease in central disc signal intensity found on T2-weighted MRIs can be a nonpathologic age-related observation but, if the result of a normal process, should be relatively uniform among all discs studied in the indi- vidual. Intervertebral osteochondrosis, or deteriorated disc,alsosometimescalled cchronicdiscopathy, dshows, on microscopic examination, total structural disorgani- zation and general replacement of normal disc tissue by Nbrosis.<br><br> Radiographically, intervertebral osteochondro- sis is characterized by narrowing of the intervertebral space, irregular disc contour often associated with bulg- ing,multidirectionalosteophytesofteninvolvingthecen- tral spinal canal and foramina, endplate erosions with reactive osteosclerosis, and chronic vertebral body bone marrow changes. On T2-weighted images, the central discsignalintensityisusuallymarkedlydecreased,andat distinct variance, to that seen in unaffected discs of the same individual. The distinction is made at the time of the reading and does not imply that early manifestations of a pathologic process are always distinguishable from changes of normal aging.<br><br> Herniated Disc The needs of common practice make necessary a diag- nostic term that covers the various permutations of disc material displaced beyond the intervertebral disc space. Herniated disc, herniated nucleus pulposus, ruptured disc, prolapsed disc (used nonspeciNcally), protruded disc (used nonspeciNcally), and bulging disc (used non- speciNcally)haveallbeenusedintheliteratureinvarious ways to denote imprecisely deNned displacement of disc material beyond the interspace. The absence of clear un- derstanding of the meaning of these terms and lack of deNnition of limits that should be placed on an ideal general term have created a great deal of confusion in clinical practice and in attempts to make meaningful comparisons of research studies.<br><br> For the general diagnosis of displacement of disc ma- terial, the single term that is most commonly used and creates least confusion is cherniated disc. d Attempts to avoid whatever confusion has been created by lack of deNnition of the term cherniated disc d have included the recommendation to substitute the term cdisc material beyond the interspace d (DEBIT), 4 but that is more awk- ward and runs counter to common practice. cHerniated nucleuspulposus d(HNP)isinaccuratebecausematerials other than nucleus (cartilage, fragmented apophyseal bone, fragmented anulus) are common components of displaced disc material. 6,47,48 cRupture d casts an image oftearingapartandthereforecarriesmoreimplicationof traumatic etiology than cherniation, d which conveys an image of displacement rather than disruption.<br><br> Though cprotrusion d has been used by some authors in a nonspeciNc general sense to signify any displace- ment,thetermhasamorecommonlyusedspeciNcmean- ing for which it is best reserved. cProlapse, d which has been used as a general term, as synonymous with the speciNc meaning of protrusion, or to denote inferior mi- E99 Lumbar Disc Pathology: Recommendations " North American Spine Society et al gration of extruded disc material, is not commonly used and is best proscribed. The term cbulging disc d has been used to mean many things and has caused a great deal of confusion,asdiscussedbelow;therefore,itsuseasagen- eral term to signify disc displacement should be avoided.<br><br> By exclusion of other terms, and by reasons of sim- plicity and common usage, cherniated disc d is the best general term to denote displacement of disc material. The term is appropriate to denote the general diagnostic categorywhenreferringtoaspeciNcdiscandtobeinclu- sive of various types of displacement when speaking of groups of discs. The term includes discs that may prop- erly be characterized by more speciNc terms, such as cprotruded disc d or cextruded disc. d The term cherniated disc, d as deNned in this work, refers to localized displacement of nucleus, cartilage, fragmented apophyseal bone, or fragmented anular tis- sue beyond the intervertebral disc space (disc space, in- terspace).<br><br> The interspace is deNned, craniad and caudad, by the vertebral body endplates and, peripherally, by the edges of the vertebral ring apophyses, exclusive of osteo- phytic formations. This deNnition was deemed more practical,especiallyforinterpretationofimagingstudies, than a pathologic deNnition requiring identiNcation of disc material forced out of normal position through an anular defect. Displacement of disc material, either throughafractureinthebonyendplateorinconjunction with displaced fragments of fractured walls of the verte- bral body, may be described as cherniated, d disc, al- though such description should accompany description of the fracture so as to avoid confusion with primary herniation of disc material.<br><br> Displacement of disc materi- alsfromonelocationtoanotherwithintheinterspace,as with intra-anular migration of nucleus without displace- mentbeyondtheinterspace,isnotconsideredherniation. To be considered cherniated, d disc material must be displaced from its normal location and not simply repre- sent an acquired growth beyond the edges of the apoph- yses, as is the case when connective tissues develop in gaps between osteophytic formations. Displacement, therefore, can only occur in association with disruption of the normal anulus or, as in the case of intravertebral herniation (Schmorl 9s node), a break in the vertebral body endplate.<br><br> Since details of the integrity of the anulus are often unknown, the distinction of herniation is usu- ally made by observation of displacement of disc mate- rial beyond the edges of the ring apophyses that is clo- calized, d meaning less than 50% (180 degrees) of the circumference of the disc. Generalized, meaning greater than50%,displacementofdiscmaterialbeyondthering apophyses, or adaptive changes of the apophyses and/or outer anulus to adjacent abnormality, such as may occur with scoliosis or spondylolisthesis, are not herniations. The50%cut-offlineisestablishedbywayofconvention to lend precision to terminology and does not demarcate etiology,relationtosymptoms,ortreatmentindications.<br><br> The term cbulge d refers to an apparent generalized extension of disc tissues beyond the edges of the apoph- yses. Such bulging occurs in greater than 50% of the circumference of the disc and extends a relatively short distance,usuallylessthan3mm,beyondtheedgesofthe apophyses. cBulge d describes a morphologic character- istic of various possible causes.<br><br> Bulge is a term for an image that requires a differential diagnosis. Bulging is sometimesanormalvariant(usuallyatL5-S1);canresult from advanced disc degeneration or from vertebral body remodeling (as consequent to osteoporosis, trauma, or adjacent structural deformity); can occur with ligamen- touslaxityinresponsetoloadingorangularmotion;can beanillusioncausedbyposteriorcentralsubligamentous disc protrusion; or can be an illusion from volume aver- aging (particularly with CT axial images). Bulging, by deNnition, is not a herniation.<br><br> Herniation is present if there is localized displacement of disc mate- rial, and not simply outward overlapping, as is the case with some types of bulging. Application of the term cbulging d to a disc does not imply any knowledge of etiology, prognosis, or need for treatment or necessarily imply the presence of symptoms. A disc may have more than one herniation.<br><br> A disc herniation may be present along with other degenerative changes, fractures or other abnormalities of adjacent bone, or other abnormalities of the disc. The term cher- niated disc d does not imply any knowledge of etiology, relation to symptoms, prognosis, or need for treatment. When data are sufNcient to make the distinction, a herniated disc may be more speciNcally characterized as cprotruded dor cextruded. dThesedistinctionsarebased ontheshapeofthedisplacedmaterial.Theydonotimply knowledge of the mechanism by which the changes oc- curred and, thereby, differ from deNnitions that base the distinction on whether and how disc material has passed through a defect in the anulus.<br><br> Protruded Discs A disc is cprotruded, d if the greatest plane, in any direction, between the edges of the disc material beyond the disc space is less than the distance between the edges of the base, when measured in the same plane. The term cprotrusion d is only appropriate indescribingherniateddiscmaterial,asdiscussedabove. Protrusions may be cfocal d or cbroad-based. d The distinction between focal and broad-based is arbitrarily set at 25% of the circumference of the disc.<br><br> Protrusions with a base less than 25% (90 degrees) of the circumfer- ence of the disc are cfocal. d If disc material is herniated so that the protrusion encompasses 25% to 50% of the circumference of the disc, it is considered cbroad-based protrusion. d Extruded Discs The term cextruded d is consistent with the lay language meaning of material forced from one domain to another through an aperture. With refer- ence to a disc, the test of extrusion is the judgment that, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base measured in thesameplane;orwhennocontinuityexistsbetweenthe E100 Spine " Volume 26 " Number 5 " 2001 disc material beyond the disc space and that within the disc space. Extruded disc material that has no continuity with the disc of origin may be further characterized as csequestrated. d A sequestrated disc is a subtype of cex- truded disc d but, by deNnition, can never be a cprotrud- ed disc. d Disc material that is displaced away from the site of extrusion, regardless of continuity, may be called cmigrated, datermthatisusefulfortheinterpretationof imaging studies because it is often impossible from im- ages to know if continuity exists.<br><br> The use of the distinction between cprotrusion d and cextrusion d is optional and some observers may prefer to use, in all cases, the more general term cherniation. d Further distinctions can often be made regarding con- tainment,continuity,volume,composition,andlocation of the displaced disc material. Containment/Continuity Herniated disc material can be ccontained d or cuncontained. d The test of containment is whether the displaced disc tissues are wholly held within intact outer anulus. A disc with a ccontained d herniation would not leak into the vertebral canal Ouid that has been injected into the disc.<br><br> Although the poste- rior longitudinal ligament and/or peridural membrane may partially cover extruded disc tissues, such discs are not considered ccontained d unless the outer anulus is intact. Strictly speaking, containment refers to the integ- rity of the outer anulus covering the disc herniation. The technical limitations of currently available noninvasive imaging modalities (CT and MRI) usually preclude the distinction of a contained from an uncontained disc her- niation.<br><br> Discography does not allow one to distinguish a containingcapsuleconsistingofbothanularNbersandlon- gitudinalligamentNbersfromoneconsistingonlyoflongi- tudinal ligament Nbers, and essentially only allows one to separate a cleaking disc d from a cnonleaking disc. d Displaceddiscfragmentsaresometimescharacterized as cfree. d A cfree fragment d is synonymous with a cse- questrated fragment d and not the same as cuncon- tained, d as the latter refers only to the integrity of the outer anulus and has no inference as to the continuity of the displaced disc material with the parent disc. A frag- ment should be considered cfree, d or csequestrated, d only if there is no remaining continuity of disc material between it and the disc of origin. The term cmigrated d disc or fragment refers to dis- placement of disc material away from the opening in the anulus through which the material has extruded.<br><br> Some migrated fragments will be sequestrated, but the term migrated refers only to position and not to continuity. Referring to the posterior longitudinal ligament (PLL), some authors have distinguished displaced disc material as csubligamentous, d cextraligamentous, d ctransligamentous, d or cperforated. d When the distinc- tionbetweentheouteranulusandthePLLisunclearand a fragment is under such a blended structure (sometimes called ccapsule d),ithasbeencalled csubcapsular. dIfthe peridural membrane alone surrounds the displaced disc material, the displacement is sometimes called csub- membranous. d Such permutations of continuity, con- tainment,andrelationshipstoligamentsandmembranes arereNnementsthatmaysuitcertainpurposesbutdonot supersede the basic deNnition of disc herniation and the major subcategorizations of extrusion and protrusion. Volume and Composition of Displaced Material A scheme to deNne the degree of canal compromise produced by disc displacement should be practical, objective, reason- ably precise, and clinically relevant.<br><br> A simple scheme that fulNlls the criteria utilizes measurements taken from an axial section at the site of the most severe compro- mise. Canal compromise of less than one third of the canal at that section is cmild d; between one and two thirds is cmoderate d; and over two thirds is csevere. d The same grading can be applied for foraminal involvement. Such characterizations of volume describe only the cross- sectional area at one section and do not account for total volume of displaced material, proximity to, compressionanddistortionofneuralstructures,orother potentially signiNcant features, which the observer may further detail by narrative description.<br><br> Composition of the displaced material may be char- acterized by such terms as cnuclear, d ccartilaginous, d cbony, d ccalciNed, d cossiNed, d ccollagenous, d cscarred, d cdesiccated, d cgaseous, d or cliqueNed. d Clinical signiNcance related to the observation of vol- ume and composition depends on correlation with clin- ical data and cannot be inferred from morphologic data alone. Location Bonneville proposed a useful and simple al- pha-numerical system to classify, according to location, the position of disc fragments that have migrated in the horizontal or sagittal plane. 2,3 Using anatomic bound- aries familiar to surgeons, Wiltse proposed another sys- tem.<br><br> 15,45 Anatomic czones d and clevels d are deNned us- ingthefollowinglandmarks:medialedgeofthearticular facets; medial, lateral, upper, and lower borders of the pedicles; and coronal and sagittal planes at the center of the disc (Figure 14). On the horizontal (axial) plane, these landmarks determine the boundaries of the ccen- tral zone, d the csubarticular zone, d the cforaminal zone, d the cextraforaminal zone, d and the canterior zone, d respectively (Figure 15). On the sagittal (cranio- caudal)plane,theydeterminetheboundariesofthe cdisc level, d the cinfra-pedicular level, d the cpedicular level, d andthe csupra-pedicularlevel, drespectively(Figure16).<br><br> The method is not as precise as drawings depict because borderlines such as the medial edges of facets and the wallsofthepediclesarecurved,butthemethodissimple, practical, and in common usage. Moving from central to right lateral in the axial (hor- izontal) plane, location may be deNned as ccentral, d cright central, d cright subarticular, d cright foraminal, d or crightextraforaminal. dTheterm cparacentral disless precise than deNning cright central d or cleft central, d E101 Lumbar Disc Pathology: Recommendations " North American Spine Society et al but is useful in describing groups of discs that include both, or when speaking informally when the side is not signiNcant. For reporting of image observations of a speciNc disc, cright central d or cleft central d should supersedeuseoftheterm cparacentral. dTheterm cfar lateral d is sometimes used synonymously with cextraforaminal. d In the sagittal plane, location may be deNned as cdis- cal, d cinfra-pedicular, d csupra-pedicular, d or cpedicu- lar. d In the coronal plane, canterior, d in relationship to the disc, means ventral to the midcoronal plane of the centrum.<br><br> Reporting When interpretations are made using clinical data, the nature of the clinical data and degree of conNdence in them may be appropriate parts of the report. The report should distinguish interpretations that are made on purely morphologic grounds from those using clinical data. The sources of the morphologic data should be described.<br><br> Reportsshouldclassifyeachdiscexaminedintobroad diagnostic categories. Further speciNcity may be appro- priate depending on the data and the purpose of the examination. The ability to distinguish between various forms of herniation and between broad-based protrusion and bulging depends on the adequacy of available imaging data and the judgment of the interpreter.<br><br> Likewise, knowing whether there is a thin thread of continuity between displaced disc material and disc of origin, or whether there is a small lapse in the integrity of the outer Nbers of anulus, may not be possible, except by surgical observation. Interpretations are made with various degrees of con- Ndence. Statement of the degree of conNdence is an im- portant component of communication.<br><br> The reporter should characterize the interpretation as cDeNnite d if there is no doubt, cProbable d if there is some doubt but the likelihood is greater than 50%, and cPossible d if there is reason to consider but the likelihood is less than 50%. The source and quality of the data are important qualiNers of the degree of conNdence. It may be appro- priate to characterize the interpretation with one degree ofconNdencebasedonmorphologiccriteriaandanother if clinical data are considered.<br><br> If the interpreter has in- Figure 14. Coronal drawing illus- trating the main anatomic czones d and clevels d. (Reprinted with permission.<br><br> 45 ) E102 Spine " Volume 26 " Number 5 " 2001 formationenoughtodoso,heorshemayfurthersuggest that the imaging Nndings are, or are not, related to the patient 9s symptoms, but the descriptive terms and diag- nosticcategoriesproposedinthismodelarenotmeantto infer any relationship to symptoms or need for treat- ment. Suggestions for additional studies to improve the level of conNdence are often appropriate. Coding The International ClassiNcation of Diseases (ICD) has been published under various names since 1900.<br><br> Begin- ning in 1948, the World Health Organization (WHO) revised ICD approximately every 10 years. The 9th Re- vision (ICD-9) 45 was due for revision in 1987, but the Nrst volume, the Tabular List, of the revision (ICD-10) was not prepared until 1992 and, as of 2000, has not been implemented in the United States. In practice, most coding in the United States follows a modiNcation, the International ClassiNcation of Diseases, 9th Revision, Clinical ModiNcation (ICD-9-CM), 42 which is ofNcially updated in October of each year.<br><br> Attempts to provide more speciNc coding for spinal disorders, such as that of the North American Spine Society, 13 have not been widely utilized because medical care providers and hos- pitals must use ICD-9-CM for reimbursement from gov- ernment and private insurers. A modiNcation of WHO 9s Fascicle V, Surgical Proce- dures, called the ICD-9-CM Procedure ClassiNcation, published as Volume 3 to ICD-9-CM, 42 is used in the United States primarily by hospitals for coding proce- dures and complications that occur during hospitaliza- tion. Its validity has been studied with regard to spine procedures.<br><br> 10,11 In the United States, for coding of ex- amination, management, and procedures to care for spi- nal disorders, most physicians use the Current Proce- dural Terminology (CPT), 1 updated yearly by the American Medical Association. In ICD-9-CM, the three-digit diagnosis code 722. is termed cIntervertebral disc disorders. d A fourth digit, following the decimal is used variously to specify site or type of pathology.<br><br> The Nrst four subcategorizations (722.0, 722.10, 722.11, and 722.2) are for cervical, thoracic, lumbar, or site-unspeciNed cDisplacement of intervertebral disc without myelopathy. d Listed as cInstructional Nota- tions, dbywayofexamplesofwhatmaybeincluded,are cDiscogenicSyndrome,HerniationofNucleusPulposus, Intervertebral Disc Extrusion, Prolapse, Protrusion, Rupture,andNeuritisorRadiculitisduetodisplacement or rupture of intervertebral disc. d The fourth subcatego- rization, 722.3, is designated cSchmorl 9s nodes. d Subcategorizations 722.4, 722.5, and 722.6 are for cDegeneration of Intervertebral Disc d in the cervical, thoracicorlumbar,andunspeciNedregions,respectively. Instructional Notations specify inclusion of cdegenera- Figure 15. Schematic representa- tion of the anatomic czones d iden- tiAed on axial images.<br><br> The anterior zone (not illustrated) is delineated from the extraforaminal zone by an imaginary coronal line in the cen- ter of the vertebral body. (Adapted with permission. 45 ) Figure 16.<br><br> Schematic representa- tion of the anatomic clevels d iden- tiAed on cranio-caudal images. (Adapted with permission. 45 ) E103 Lumbar Disc Pathology: Recommendations " North American Spine Society et al tive disc disease d and cnarrowing of intervertebral disc or space. d Subcategorization 722.7 is labeled cIntervertebral disc disorder with myelopathy. d It does not specify dis- placement of the disc.<br><br> Fifth digits are added for regional location. Subcategorization 722.8 is labeled cPostlami- nectomy syndrome. d cOther and unspeciNed disc disorder d is the diagnos- tic label of 722.9, with Instructional Notations to in- clude ccalciNcation of intervertebral cartilage or disc d and cDiscitis. d Observations of imaging variations of unknown signiNcance can be coded 793.7, which ICD- 9-CM describes as cNonspeciNc abnormal Nndings on radiologic and other examination of body structure, Musculoskeletal. d The International ClassiNcation of Diseases, 10th re- vision, lists intervertebral disc disorders under the cOth- er Dorsopathies d Section. Digits after the decimal for codes cM50. d and cM51. d provide separate codes for cervical or lumbar/thoracic cdisc disorder with myelop- athy, d cdisc disorder with radiculopathy, d cother disc displacement, d cother disc degeneration, d cother disc disorders, d and cSchmorl 9s nodes. d Translation of the disc nomenclature recommended here into ICD-9-CM codes presents relatively little difN- culty.<br><br> Discs characterized herein as cherniated d should be coded under 722.0, 722.10, 722.11, or 722.2. A disc described as cbulging d without further speciNcation as to the cause of the bulging should not be coded as a displacement, but, like other observations of uncertain signiNcance as 722.9 cother and unspeciNed disc disor- der d or as 793.7, cnonspeciNc abnormal Nndings on ra- diographic examination d (musculoskeletal). Intraverte- bral herniation (Schmorl 9s node) should be coded 722.3.<br><br> Although ICD-9-CM language characterizing cinterver- tebral disc disorder with myelopathy d does not specify that the disc is displaced, that is the logical implication, soitisbettertocodeadisplaceddisccausingmyelopathy as 722.7, rather than choose 722.0/1/2, which would introduce the contradictory language of cwithout my- elopathy. d Various permutations of disc degeneration shouldbecoded722.4/5/6andcanbeadded,whereappro- priate,tocodesthatdescribedisplacement.NonspeciNcdis- citis and other not-elsewhere-classiNed disc disorders should be coded 722.9; except, of course, when speciNc pathogens, neoplastic disorders, or nondegenerative ar- thridites are known, in which case the speciNc diagnosis should be used, instead of, or in addition to, 722.9. Translation of recommended terminology into ICD-10 is also fairly straightforward and follows the same principles. The International ClassiNcation of Dis- eases, 10th revision, takes the demands on clinical knowledgeastepfurtherbyprovidingseparatecodesfor cdisc disorder with radiculopathy d (M50.1, M51.1), cdisc disorder with myelopathy d (M50.0, M51.0), and cother disc displacement d (M50.2, M51.2).<br><br> The empha- sis is on the clinical neurologic status with cdisorder d and cdisplacement d being used almost synonymously, whichcontrastswiththeaimofnomenclaturetoprovide speciNcitytodiscpathologyandmorphology.Thediffer- ingaxesofcodingandterminologyrequirementsarebest bridged by assuming that disc herniations are coded as cother disc displacement d unless known to accompany radiculopathyormyelopathy,inwhichcasetheyarebest coded as cdisc disorder with radiculopathy d or cdisc disorder with myelopathy. d Like ICD-9-CM, ICD-10 provides speciNc codes for Schmorl 9s nodes (M51.4) and for disc degeneration (M50.3, M51.3). ICD-10 provides separate codes for cother speciNed intervertebral disc disorders d(M50.8, M51.8) and for cintervertebral disc disorder, unspeciNed d (M50.9, M51.9). Sciatic pain, lumbago, regional spinal pain syn- dromes, and radiculopathies and myelopathies not known to be caused by disc herniation are provided unique codes in both ICD-9-CM and ICD-10.<br><br> Codes for disc disorders or displacements should only be used when a diagnosis of abnormal disc morphology is intended. Procedural coding systems present little challenge to diagnostic nomenclature, since diagnoses are inferred butnotdeNnedbyproceduralcodes.CPTprovidescodes for examination, management, and procedural services, including, in some instances the naming of diagnoses to help deNne the procedure; for example, operations to remove displaced disc material are characterized as cex- cision of herniated intervertebral disc d or as cdiskec- tomy, d as descriptors of certain procedures done through a laminotomy or laminectomy approach (63001-63048). Procedure 62287 is characterized as caspiration procedure, percutaneous, of nucleus pulpo- sus of intervertebral disc. d Glossary Note Some terms and de2nitions included in this Glossary are not recommended as preferred terminology but are in- cluded to facilitate interpretation of vernacular and, in some cases, improper use.<br><br> Preferred de2nitions are listed 2rst. Confusing or inaccurate alternative de2nitions are placed in brackets and designated as cNon-Standard. d aging disc Disc demonstrating features of normal ag- ing. Spondylosis deformans possibly represents the nor- mal aging process.<br><br> anterior displacement Displacement of disc tissues be- yond the disc space into the anterior zone. anterior zone Peridiscal zone that is anterior to the midcoronal plane of the vertebral body. anulus, annulus (abbreviated form of annulus fibrosus) A multilaminated ligament surrounding the periphery of each disc space, attaching, craniad and caudad, to end- plate cartilage and ring apophyseal bone and blending centrally with nucleus pulposus.<br><br> Note: Either anulus or annulusiscorrectspelling. NominaAnatomica usesboth forms, whereas Terminologia Anatomica states canulus E104 Spine " Volume 26 " Number 5 " 2001 Nbrosus. d 18,21 Fibrosus has no correct alternative spell- ing; Nbrosis has a different meaning and is incorrect in this context. asymmetric bulge Presence of outer anulus beyond the planeofthediscspace,moreevidentinonesectionofthe periphery of the disc than another, but not sufNciently focal to be characterized as a protrusion.<br><br> Note: Asym- metric bulge is a morphologic observation of various potential causes and is not a diagnosis. See: bulge. balloon disc (colloquial) Diffuse displacement of nu- cleus through the vertebral endplate, commonly seen in severe osteoporosis.<br><br> base (of displaced disc) Thecross-sectionalareaofdisc material at the outer margin of the disc space of origin, where disc material beyond the disc space is continuous with disc material within the disc space. In the cranio- caudaldirection,thelengthofthebasecannotexceed,by deNnition, the height of the intervertebral space. broad-based protrusion Protrusion of disc material ex- tending beyond the outer edges of the vertebral body apophyses over an area greater than 25% (90 degrees) and less than 50% (180 degrees) of the circumference of the disc.<br><br> See protrusion. Note: Broad-based protrusion refersonlytodiscsinwhichdiscmaterialhasdisplacedin association with localized disruption of the anulus and not to generalized (over 50% or 180 degrees) apparent extension of disc tissues beyond the edges of the apoph- yses. If the base is less than 25%, it is called cfocal pro- trusion. dApparentextensionofdiscmaterial,formation of additional connective tissue between osteophytes, or overlapping of nondisrupted tissue beyond the edges of the apophyses of over 50% of the circumference of the disc may be described as bulging.<br><br> See: bulging disc, focal protrusion. bulging disc, bulge (n), bulge (v). 1.<br><br> A disc in which the contour of the outer anulus extends, or appears to ex- tend, in the horizontal (axial) plane beyond the edges of the disc space, usually over greater than 50% (180 de- grees) of the circumference of the disc and usually less than 3 mm beyond the edges of the vertebral body ap- ophyses. 2. (Non-Standard) [A disc in which the outer margin extends over a broad base beyond the edges of the disc space.] 3.<br><br> (Non-Standard) [Mild, smooth dis- placement of disc, whether focal or diffuse.] 4. (Non- Standard) [Any disc displacement at the discal level.] Note: Bulging is an observation of the contour of the outer disc and is not a speciNc diagnosis. Bulging has been variously ascribed to redundancy of anulus second- ary to loss of disc space height, ligamentous laxity, re- sponse to loading or angular motion, remodeling in re- sponsetoadjacentpathology,unrecognizedandatypical herniation, and illusion from volume averaging on CT axial images.<br><br> Bulging may or may not represent patho- logic change, physiologic variant, or normalcy. Bulging is not a form of herniation; discs known to be herniated should bediagnosed as herniation or,when appropriate, as speciNc types of herniation. See: herniated disc, pro- truded disc, extruded disc.<br><br> capsule CombinedNbersofanulusandposteriorlon- gitudinal ligament. Note: The interface between outer anulus and posterior longitudinal ligament can be indis- tinguishable, making useful the term ccapsule d and the derivative csubcapsular, d which refers to disc tissue be- neath the capsule. cavitation Spaces, cysts, clefts, or cavities formed within the nucleus and inner anulus from disc degeneration.<br><br> central zone Zone within the vertebral canal between sagittal planes through the medial edges of each facet. Note: The center of the central zone is a sagittal plane through the center of the vertebral body. The zones to either side of the center plane are right central and left central , which are preferred terms when the side is known, as when reporting imaging results of a speciNc disc.<br><br> When the side is unspeciNed, or grouped with both right and left represented, the term paracentral is appropriate. chondrosis See intervertebral osteochondrosis. chronic disc herniation Disc herniation with presence of calciNcation, ossiNcation, or gas accumulation within the displaced disc material, suggesting that the hernia- tion is not of recent origin.<br><br> Note: The term implies the presence of calciNcation, ossiNcation, or gas accumula- tion and should not be used for herniations of soft disc material,regardlessofthedurationofdisplacement.See: degenerated disc, hard disc. claw osteophyte Bony outgrowth arising very close to the disc margin, from the vertebral body apophysis, di- rected, with a sweeping conNguration, toward the corre- sponding part of the vertebral body opposite the disc. collagenized disc or nucleus A disc in which the muco- polysaccharide of the nucleus has been replaced by N- brous tissue.<br><br> communicating disc, communication (n), communicate (v) Interruption in the periphery of the disc, so that Ouid injected into the disc space could Oow into the vertebral canal and thus into contact with displaced disc material. Note: Communication refers to the status of displaced disc tissues with reference to the parent disc. Contain- ment refers to the integrity of the anulus as container of disc tissues.<br><br> Uncontained, displaced disc tissues could be noncommunicating if the displaced tissue is sealed off by peridural membrane or by healing of the tear in the anulus. concentric tear TearorNssureoftheanuluscharacter- ized by separation, or break, of anular Nbers, in a plane roughly parallel to the curve of the periphery of the disc, E105 Lumbar Disc Pathology: Recommendations " North American Spine Society et al creating Ouid-Nlled spaces between adjacent anular la- mellae. See: radial tears, transverse tears.<br><br> contained herniation, containment (n), contain (v) 1. Dis- placed disc tissue that is wholly within an outer perime- ter of uninterrupted outer anulus or capsule. 2.<br><br> (Non- standard) [A disc with its contents mostly, but not wholly, within anulus or capsule.] 3. (Non-Standard) [A disc with displaced elements contained within any inves- titure of the vertebral canal.] Note: The preferred mean- ing encompasses disc tissues that are enclosed by dis- tended portions of the outer anulus or composite of Nbers of the anulus and posterior longitudinal ligament. A disc whose substance is less than wholly contained by anulusisuncontained,asisadiscoutsideofanularNbers but under a distinct posterior longitudinal ligament or peridural membrane.<br><br> Designation of a disc as contained, or uncontained, should deNne the integrity of the anulus enclosing the disc, although such distinction may not be possible with currently available imaging methods. continuity 1. Connection of displaced disc tissue by a bridge of disc tissue, however, thin, to tissue within the disc of origin.<br><br> 2. (Non-Standard) [Connection of dis- placeddisplaceddisctissuebyasubstantialbridgeofdisc tissue to disc within the disc of origin]. 3.<br><br> (Non- Standard) [Connection of displaced disc tissue by any tissue to disc tissue within the disc or origin.] Note: Tenuous attachments, beyond recognition by most imaging methods, may have signiNcance to the sur- geon or endoscopist. Bridges of peridural membrane, or scar, do not represent continuity. See sequestration.<br><br> Crock disc See internal disc disruption syndrome. degenerated disc, degeneration (n), degenerate (v) 1. Changes in a disc characterized by desiccation, Nbrosis and cleft formation in the nucleus, Nssuring and muci- nous degeneration of the anulus, defects and sclerosis of endplates, and/or osteophytes at the vertebral apophy- ses.<br><br> 2. Imaging manifestations commonly associated with such changes. 3.<br><br> (Non-Standard) [Changes in a disc related to aging.] Note: Either of the Nrst two deNnitions may be correct, depending on context. Clinical features must be considered to determine whether degenerative changes are pathologic and what may or may not have contributed to their development. The term degenerated disc,initself,doesnotinferknowledgeofcause,relation- ship to aging, presence of symptoms, or need for treat- ment.<br><br> See intervertebral osteochondrosis, spondylosis, spondylosis deformans. degenerative disc disease 1. A clinical syndrome char- acterized by manifestations of disc degeneration and symptoms thought to be related to those changes.<br><br> 2. (Non-Standard) [Abnormal disc degeneration.] 3. (Non- Standard) [Imaging manifestations of degeneration greater than expected, considering the age of the pa- tient].<br><br> Note: Causal connections between degenerative changes and symptoms are often difNcult clinical distinc- tions. The term carries implications of illness that may not be appropriate if the only manifestations are from imaging. The preferred term for description of imaging manifestations alone, or imaging manifestations of un- certain relationship to symptoms, is degenerated disc rather than degenerative disc disease.<br><br> delamination Separation of anular Nbers along planes parallel to the periphery of the disc, thought to represent separation of laminated layers of the outer anulus Nbrosus. desiccated disc 1. Disc with reduced water content, usually primarily of nuclear tissues.<br><br> 2. Imaging manifes- tations of reduced water content of the disc; or apparent reducedwatercontent,asfromalterationsintheconcen- tration of hydrophilic glycosaminoglycans. disc (disk) Complex structure composed of nucleus, anulus, cartilaginous endplates, and vertebral body ring apophyseal attachments of anulus.<br><br> Note: Most English language publications use the spelling disc more often than disk. 12 Nomina Anatomica designates the struc- tures as cDisci intervertebrales d and Terminologia Ana- tomica as cdiscus intervertebralis/Intervertebral disc. d 18,21 disc of origin Disc from which a displaced fragment originated. Syn: parent disc Note: Since displaced frag- ments often contain tissues other than nucleus, disc of origin is preferred to nucleus of origin.<br><br> Parent disc is synonymous, but more colloquial. disc space Space limited, craniad and caudad, by the endplates of the vertebrae and peripherally by the edges of the vertebral body ring apophyses exclusive of osteo- phytes. Syn: intervertebral disc space.<br><br> disc space height The distance between t