RADIOLOGICAL TERMS IN DEGENERATIVE DISC DISEASE:
Aging disc: Disc demonstrating the features of normal aging. Spondylosis deformans possibly represents the normal aging process.
Anterior displacement: Displacement of disc tissues beyond the disc space into the anterior zone.
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. Note: Either anulus or annulus is correct spelling. Nomina Anatomica uses both forms whereas Terminologia Anatomica states “annulus fibrosus.” Fibrosus, has no correct alternative spelling; fibrosis has a different meaning and is incorrect in this context.
Asymmetric bulge: Presence of outer annulus beyond the plane of the disc space, more evident in one section of the periphery of the disc than another, but not sufficiently focal to be characterized as a protrusion. Note: Asymmetric bulge is a morphologic observation of various potential causes and is not a diagnosis. See: bulge.
Balloon disc (colloquial): Diffuse displacement of nucleus through the vertebral end plate, commonly seen in severe osteoporosis.
Base (of displaced disc): 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. In the cranio-caudal direction, the length of the base cannot exceed, by definition, the height of the intervertebral space.
Broad-based protrusion: Herniation of disc material extending 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. See protrusion. Note: Broad based protrusion refers only to discs in which disc material has displaced in association with localized disruption of the annulus and not to generalized (over 50% or 180 degrees) apparent extension of disc tissues beyond the edges of the apophyses. If the base is less than 25%, it is called “focal protrusion.” Apparent extension of disc material, formation of additional connective tissue between osteophytes, or overlapping of non-disrupted tissue beyond the edges of the apophyses of over 50% of the circumference of the disc may be described as bulging. See: bulging disc, focal protrusion.
Bulging disc, bulge (n), bulge (v): 1. A disc in which the contour of the outer anulus extends, or appears to extend, in the horizontal (axial) plane beyond the edges of the disc space, over greater than 50% (180 degrees) of the circumference of the disc and usually less than 3mm beyond the edges of the vertebral body apophyses. 2. (Non-Standard) [A disc in which the outer margin extends over a broad base beyond the edges of the disc space.] 3. (Non-Standard) [Mild, smooth displacement 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 specific diagnosis. Bulging has been variously ascribed to redundancy of annulus secondary to loss of disc space height, ligamentous laxity, response to loading or angular motion, remodeling in response to adjacent pathology, unrecognized and atypical herniation, and illusion from volume averaging on CT axial images. Bulging may or may not represent pathologic change, physiologic variant, or normalcy. Bulging is not a form of herniation; discs known to be herniated should be diagnosed as herniation or, when appropriate, as specific types of herniation. See: herniated disc, protruded disc, extruded disc.
Capsule: Combined fibers of annulus and posterior longitudinal ligament. Note: The interface between outer annulus and posterior longitudinal ligament can be indistinguishable, making useful the term “capsule” and the derivative “sub-capsular,” which refers to disc tissue beneath the capsule.
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 specific disc. When the side is unspecified, or grouped with both right and left represented, the term paracentral is appropriate.
Chronic disc herniation: 1. Disc herniation with presence of calcification, ossification, or gas accumulation within the displaced disc material, suggesting that the herniation is not of recent origin. Note: The term implies the presence of calcification, ossification, or gas accumulation and should not be used for herniations of soft disc material, regardless of the duration of displacement. See: degenerated disc, hard disc.
Claw osteophyte: Bony outgrowth arising very close to the disc margin, from the vertebral body apophysis, directed, with a sweeping configuration, toward the corresponding part of the vertebral body opposite the disc.
Communicating disc, communication (n), communicate (v): Interruption in the periphery of the disc, so that fluid injected into the disc space could flow 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. Containment refers to the integrity of the annulus as container of disc tissues. 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 annulus.
concentric tear: Tear or fissure of the annulus characterized by separation, or break, of anular fibers, in a plane roughly parallel to the curve of the periphery of the disc, creating fluid-filled spaces between adjacent anular lamellae. See: radial tears, transverse tears.
Contained herniation, containment (n), contain (v): 1. Displaced disc tissue that is wholly within an outer perimeter of uninterrupted outer annulus or capsule. 2. (Non-standard) [A disc with its contents mostly, but not wholly, within annulus or capsule.] 3. (Non-Standard) [A disc with displaced elements contained within any investiture of the vertebral canal.] Note: The preferred meaning encompasses disc tissues that are enclosed by distended portions of the outer annulus or composite of fibers of the annulus and posterior longitudinal ligament. A disc whose substance is less than wholly contained by annulus is uncontained, as is a disc outside of anular fibers but under a distinct posterior longitudinal ligament or peridural membrane. Designation of a disc as contained, or uncontained, should define the integrity of the annulus enclosing the disc, though such distinction may not be possible with currently available imaging modalities.
Continuity: 1. Connection of displaced disc tissue by a bridge of disc tissue, however thin, to tissue within the disc of origin. 2. (Non-Standard) [Connection of displaced displaced disc tissue by a substantial bridge of disc tissue to disc within the disc of origin]. 3. (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 significance to the surgeon or endoscopist. Bridges of peridural membrane, or scar, do not represent continuity. See sequestration.
degenerated disc, degeneration (n), degenerate (v): 1. Changes in a disc characterized by desiccation, fibrosis and cleft formation in the nucleus, fissuring and mucinous degeneration of the annulus, defects and sclerosis of end-plates, and/or osteophytes at the vertebral apophyses. 2. Imaging manifestations commonly associated with such changes. 3. (Non-Standard) [Changes in a disc related to aging.] Note: Either of the first two definitions may be correct, depending upon 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, in itself, does not infer knowledge of cause, relationship to aging, presence of symptoms, or need for treatment. See intervertebral osteochondrosis, spondylosis, spondylosis deformans.
Degenerative disc disease(DDD): 1. A clinical syndrome characterized by manifestations of disc degeneration and symptoms thought to be related to those changes. 2. (Non-Standard) [Abnormal disc degeneration.] 3. (Non-Standard) [Imaging manifestations of degeneration greater than expected, considering the age of the patient]. Note: Causal connections between degenerative changes and symptoms are often difficult clinical distinctions. 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 uncertain relationship to symptoms, is degenerated disc rather than degenerative disc disease.
Delamination: Separation of anular fibers along planes parallel to the periphery of the disc, thought to represent separation of laminated layers of the outer anulus fibrosus.
Desiccated disc: 1. Disc with reduced water content, usually primarily of nuclear tissues. 2. Imaging manifestations of reduced water content of the disc; or apparent reduced water content, as from alterations in the concentration of hydrophilic glycosaminoglycans.
Disc (disk): Complex structure composed of nucleus, anulus, cartilaginous end-plates, and vertebral body ring apophyseal attachments of anulus. Note: Most English language publications use the spelling disc more often than disk.12 Nomina Anatomica designates the structures as “Disci intervertebrales” and Terminologia Anatomica as “discus intervertebralis/Intervertebral disc.”18,21
Disc of origin: Disc from which a displaced fragment originated. Syn: parent disc. Note: Since displaced fragments often contain tissues other than nucleus, disc of origin is preferred to nucleus of origin. “Parent disc” is synonymous, but more colloquial.
Disc space: 1. Space limited, craniad and caudad, by the end-plates of the vertebrae and peripherally by the edges of the vertebral body ring apophyses exclusive of osteophytes. Syn: intervertebral disc space.
Discogenic vertebral sclerosis: Increased bone density and calcification adjacent to the end-plates of the vertebrae craniad and caudad to a degenerated disc, usually a manifestation of intervertebral osteochondrosis.
Displaced disc: A disc in which disc material is beyond the outer edges of the vertebral body ring apophyses (exclusive of osteophytes) of the craniad and caudad vertebrae, or, as in the case of intravertebral herniation, penetrated through the vertebral body end-plate. Note: Displaced disc is a general term that does not imply knowledge of the underlying pathology, cause, relationship to symptoms, or need for treatment. The term includes, but is not limited to, disc herniation and disc migration.See: herniated disc, migrated disc.
Extra-foraminal zone: The zone beyond the sagittal plane of the lateral edges of the pedicles, having no well-defined lateral border. Syn: far lateral zone, far-out zone.
Extra-ligamentous: Posterior or lateral to the posterior longitudinal ligament. Note: Extra-ligamentous disc refers to displaced disc tissue that is located lateral, or posterior to the posterior longitudinal ligament. If the disc has extruded through the posterior longitudinal ligament it is sometimes called “trans-ligamentous” or “perforated,” and if through the peridural membrane, it is sometimes refined to as “trans-membranous.”
Extruded disc, extrusion (n), extrude (v): A herniated disc in which, 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 in the same plane, or when no continuity exists between the disc material beyond the disc space and that within the disc space. Note: The preferred definition is consistent with the common language image of extrusion as an expulsion of material from a container through and beyond an aperture. Displacement beyond the outer anulus of disc material with any distance between its edges greater than the distance between the edges of the base distinguishes extrusion from protrusion. Distinguishing extrusion from protrusion by imaging is best done by measuring the edges of the displaced material and remaining continuity with the disc of origin, whereas relationship of the displaced disc material to the aperture through which it has passed is more readily observed surgically. Characteristics of protrusion and extrusion may co-exist, in which case the disc should be subcategorized as extruded. Extruded discs in which all continuity with the disc of origin is lost may be further characterized as sequestrated. Disc material displaced away from the site of extrusion may be characterized as migrated. See: herniated disc, migrated disc, protruded disc.
Fissure of anulus: Separations between anular fibers, avulsion of fibers from their vertebral body insertions, or breaks through fibers that extend radially, transversely, or concentrically, involving one or more layers of the anular lamellae. Syn: tear of anulus, torn anulus. Note: The terms fissure and tear are commonly used synonymously. Neither term implies any knowledge of etiology, relationship to symptoms, or need for treatment. Tear or fissure are both used to represent separations of anular fibers from causes other than sudden violent injury to a previously normal anulus, which can be appropriately termed “rupture of the anulus,” which, in turn, contrasts to the colloquial, non-standard, use of the term “ruptured disc,” referring to herniation.
Focal protrusion: Protrusion of disc material so that the base of the displaced material is less than 25% (90 degrees) of the circumference of the disc. Note: Focal protrusion refers only to herniated discs that are not extruded and do not have a base greater than 25% of the disc circumference. Herniated discs with a base greater than 25% are “broad-based protrusions.”
Foraminal zone: The zone between planes passing through the medial and lateral edges of the pedicles. Note: The foraminal zone is sometimes called the “pedicle zone,” which can be confusing because pedicle zone might also refer to measurements in the sagittal plane between the upper and lower surface of a given pedicle, which is properly called the “pedicle level.” The foraminal zone is also sometimes called “lateral zone,” which can be confusing because lateral zone can also mean extra-foraminal zone or an area including both the foraminal and extra-foraminal zones.
Free fragment: 1. A fragment of disc that has separated from the disc of origin and has no continuous bridge of disc tissue with disc tissue within the disc of origin. Syn: sequestrated disc . 2. (Non-Standard) [A fragment that is not contained within the outer perimeter of the anulus.] 3. (Non-Standard) [A fragment that is not contained within anulus, posterior longitudinal ligament, or peridural membrane.] Note: Sequestrated disc and free fragment are virtually synonymous. When referring to the condition of the disc, categorization as extruded with sub-categorization as sequestrated is preferred, whereas free fragment or sequestrum is appropriate when referring specifically to the fragment.
Hard disc: Disc displacement in which the displaced portion has undergone calcification or ossification and may be intimately associated with apophyseal osteophytes. Note: The term hard disc is most often used in reference to the cervical spine to distinguish chronic hypertrophic and reactive changes in the periphery of the disc from acute extrusion of soft, predominantly nuclear tissue. See: chronic disc herniation.
Herniated disc, herniation (n), herniate (v): 1. Localized displacement of disc material beyond the normal margins of the intervertebral disc space. 2. (Non-Standard) [Any displacement of disc tissue beyond the disc space]. Note: Localized means, by way of convention, less than 50% (180 degrees) of the circumference of the disc. Disc material may include nucleus, cartilage, fragmented apophyseal bone, or fragmented anular tissue. The normal margins of the intervertebral disc space are defined, craniad and caudad, by the vertebral body end-plates and peripherally by the edges of the vertebral body ring apophyses, exclusive of osteophytic formations. Herniated disc generally refers to displacement of disc tissues through a disruption in the anulus, the exception being intravertebral herniations (Schmorl’s nodes) in which the displacement is through vertebral end-plate. Herniated discs in the horizontal (axial) plane may be further subcategorized as protruded or extruded. Herniated disc is sometimes referred to as “herniated nucleus pulposus,” but the term herniated disc is preferred because displaced disc tissues often include cartilage, bone fragments, or anular tissues. The term “ruptured disc” is used synonymously with herniated disc, but is more colloquial and can be easily confused with violent, traumatic rupture of the anulus or end-plate. The term “prolapse” has also been used as a general term for disc displacement, but its use has been inconsistent. The term herniated disc does not infer knowledge of cause, relation to injury or activity, concordance with symptoms, or need for treatment.
High intensity zone (HIZ): Area of high signal intensity on T2-weighted magnetic resonance images of the disc, usually referring to the outer anulus. Note: High intensity zones within the posterior anular substance may reflect fissure or tear of the anulus, but do not imply knowledge of etiology, concordance with symptoms, or need for treatment.
infra-pedicular level: The level between the axial planes of the inferior edge of the pedicle craniad to the disc in question and the inferior end-plate of the vertebral body above. Syn: superior vertebral notch.
Internal disc disruption syndrome: Internal disc disruption associated with symptoms, which are thought, on clinical grounds, to be caused by the disruption. Syn: Crock disc.
Intervertebral osteochondrosis: Degenerative process of the spine involving the vertebral body end-plates, the nucleus pulposus, and the anulus fibrosus, which is characterized by disc space narrowing, vacuum phenomenon, and vertebral body reactive changes. Syn: deteriorated disc, chronic discopathy, osteochondrosis.
Intra-anular displacement: Displacement of central, predominantly nuclear, tissue to a more peripheral site within the disc space, usually into a fissure in the anulus. Syn: (Non-Standard) [intra-anular herniation], [intra-discal herniation]. Note: Intra-anular displacement is distinguished from disc herniation, in that herniation of disc refers to displacement of disc tissues beyond the disc space. Intra-anular displacement is a form of internal disruption. When referring to intra-anular displacement, it is best not to use the term “herniation” in order to avoid confusion with disc herniation.
Intra-dural herniation: A disc from which displaced tissue has penetrated, or become enclosed by, the dura so that it lies within the thecal sac.
Intra-vertebral herniation: A disc in which a portion of the disc is displaced through the end-plate into the centrum of the vertebral body. Syn: Schmorl’s node.
limbus fracture: Traumatic separation of a segment of bone from the edge of the vertebral ring apophysis at the site of anular attachment. Note: Limbus fractures of various types may be accompanied by disc herniation, usually by either focal or broad-based protrusion. They may occur into the anterior zone or posteriorly into the zones where they may compress neural tissues.
Limbus vertebrae: Separation of a segment of rim of vertebral body ring apophysis. Note: Limbus vertebrae may result from fracture or from developmental abnormalities. Limbus vertebrae is commonly seen in patients who have had Scheuermann’s Disease. The lesions may be called “rim lesions.” The term is derived from the Latin nominative limbus and genitive modifier vertebrae, thus is singular.
Marginal osteophyte: Osteophyte that protrudes from and beyond the outer perimeter of the vertebral end-plate apophysis.
Migrated disc, migration (n), migrate (v): 1. Herniated disc in which a portion of extruded disc material is displaced away from the tear in the outer anulus through which it has extruded. 2. (Non-Standard) [A herniated disc with a free fragment or sequestrum beyond the disc level.] Note: Migration refers to the position of the displaced disc material, rather than to its continuity with disc tissue within the disc of origin; therefore, it is not synonymous with sequestration.
non-marginal osteophyte: Osteophyte the occurs at sites other than the vertebral end-plate apophysis. See: marginal osteophyte.
Normal disc: 1. A fully and normally developed disc with no changes attributable to trauma, disease, degeneration, or aging. The bilocular appearance of the adult nucleus is considered a sign of normal maturation. 2. (Non-Standard) [A disc that may contain one or more morphologic variants which would be considered normal given the clinical circumstances of the patient.]. Note: Many congenital and developmental variations may be normal in that they are not associated with symptoms; certain adaptive changes in the disc may be normal considering adjacent pathology, and certain degenerative phenomena may be normal given the patient’s age; however, classification and reporting for medical purposes is best served if such discs are not considered normal. What is clinically normal for a given patient is a clinical judgment independent of the need to describe any variation in the disc itself.
Osteophytes: Focal hypertrophy of bone surface and/or ossification of soft tissue attachments to the bone.