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How's your disk illustrative glossary of degenerative disk lesions using standardized lexicon
- 1. Hows Your Disk? Illustrative Glossary of Degenerative Disk Lesions Using Standardized Lexicon SoHyun Boo, MD, and Jeffery P. Hogg, MD The growing demand for structured reporting in radiology requires acceptance and familiarity of standard terms. This article clearly summarizes and illustrates the standard lexicon and classi鍖cation scheme for degenerative lumbar disk pathology. First-year residents and veteran radiolo- gists will gain/refresh knowledge of the lexicon for stan- dard reporting. We provide an example-based illustrated glossary that contains diagrams and referenced descriptive explanations to illustrate disk lesions in the current stan- dardized lexicon. Collected cross-sectional imaging of the spine from our tertiary care institution provides a clear patient-based representation of elements in the lexicon. There is a myriad of descriptive terms for lumbar disk pathology that has been historically used, some of which may overlap and cause confusion. More and more, there is a movement toward standardizing radi- ology lexicon. This proves bene鍖cial for the referring physicians, other radiology colleagues, coding, and ultimately, the patient. In 2001, the North American Spine Society, along with the American Society of spine radiology and the American Society of Neuro- radiology, agreed on and published guidelines for classifying the different types of lumbar disk pathol- ogy. This was also endorsed by the Joint Section on Disorders of the Spine and Peripheral Nerves of the American Association of Neurological Surgeons, the Congress of Neurological Surgeons, and the Current Procedural Terminology and International Classi鍖ca- tion of Diseases Coding Committee of American Academy of Orthopedic Surgeons.1 This educational article summarizes the standard nomenclature and classi鍖cation scheme (Table 1). Speci鍖cally, the clas- si鍖cation of degenerative/traumatic lesions has histor- ically been confounding in the numerous terms used. A systematic approach is offered to help guide the evaluation of the disk lesion with provided examples. Normal Morphologically, normal adult disks have a bilocular appearance due to development of a central horizontal From the Department of Radiology, WVU Health Sciences Center, Morgantown, WV. Reprint requests: SoHyun Boo, MD, Robert C. Byrd Health Sciences Center, Box 9235 HSC, Morgantown, WV 26506. E-mail: sboo@hsc.wvu.edu. Curr Probl Diagn Radiol 2010;39:118-124. 息 2010 Mosby, Inc. All rights reserved. 0363-0188/2010/$36.00 路 0 doi:10.1067/j.cpradiol.2009.07.002 FIG 1. Normal bilocular appearing disk. TABLE 1. Classi鍖cation of disk lesions Normal Congenital/developmental variant Degenerative/traumatic lesion In鍖ammation/infection Neoplasia Morphologic variant of unknown signi鍖cance 118 Curr Probl Diagn Radiol, May/June 2010
- 2. band of 鍖brous tissue within the nucleus. Normal does not give regard to the clinical context and does not include aging, adaptive, developmental, or degen- erative changes, which may be clinically normal 25% 90属 Normal disk FIG 2. Schematic of normal disk considered as a 360-degree arc. FIG 3. Congenital developmental variant of disk which has undergone morphologic change secondary to scoliosis in this case. Generalized disk bulge 25% 90属 FIG 4. Generalized disk bulge. Disk displacement involves 肋50% (180属) of ring apophyses. central canal zone central zone (right or left) or subarticular zone nucleus pulposusannulus fibrosus foraminal zone (pedicle zone) extra-foraminal zone (far lateral zone) FIG 5. Normal disk consists of the nucleus pulposus and surrounding annulus 鍖brosus. Disk hernias can be further described in its zonal location. FIG 6. Annular tears are seen as high intensity nucleus pulposus existing through areas of separation between the dark annular 鍖bers. Intravertebral hernias are also seen. TABLE 2. Subcategories of degenerative/traumatic lesions Annular tear/鍖ssure Herniation (extrusion/protrusion) Degeneration (desiccation, spondylosis deformans, intervertebral osteochondrosis) Curr Probl Diagn Radiol, May/June 2010 119
- 3. 90属 Focal Hernia 25% 90属 Broad-based hernia 25% FIG 7. Localized displacement of disk can be a focal (禄25%) or broad-based (25-50%) hernia. 90属 Protrusion 25% or FIG 8. Protrusion type hernia. 120 Curr Probl Diagn Radiol, May/June 2010
- 4. (Fig 1).1 The normal disk can be considered as a 360-degree arc divided into 4 quadrants (Fig 2).1 Congenital Developmental Variant These abnormal disks have undergone morphologic changes to adapt to abnormal growth of the spine such as in scoliosis or spondylolisthesis (Fig 3). There is generalized displacement of disk beyond the endplates that constitutes a disk bulge. By conven- tion, bulging disks involve 肋50% (180属) of the ring apophyses (Fig 4).1 By this standard lexicon, a bulge is not a hernia. Degenerative/Traumatic Degenerative/traumatic change in the disk is a broad category that again is purely descriptive and identi鍖es and does not imply any relationship to the clinical context, pathology, or need for treatment. Several subcategories of degenerative/traumatic lesions are identi鍖ed in Table 2. 90属 Extrusion 25% or FIG 9. Extrusion type hernias. Curr Probl Diagn Radiol, May/June 2010 121
- 5. Generalized disk bulge 25% Identify displacement of disk. (generalized vs.. localized) Is displacement > 50% (180 degrees) of the edge of the ring apophyses? YES NO Is displacement < 25%? Are the widest edges of displaced disk, in any plane, less than the distance between the edges of the hernia base? Localized Hernia Focal Broad-based Focal Extrusion Focal Protrusion Are the widest edges of displaced disk, in any plane, greater than the distance between the edges of the hernia base? Broad-based Extrusion Broad-based Protrusion ONSEY YES YESNO NO 90属 Broad-based hernia 25% 90属 Focal hernia 25% Generalized bulge 90属 FIG 10. Algorithm for analysis of disk displacement. 122 Curr Probl Diagn Radiol, May/June 2010
- 6. Annular Tears Annular tears or 鍖ssures describe breaks or separation between the dark annular 鍖bers that extend concentri- cally, transversely, or radially, allowing the more high intensity nucleus to exit through (Figs 5 and 6).2,3 Intravertebral hernia is also seen in Fig 6. Disk Hernias By convention, a hernia is de鍖ned as localized dis- placement of disk material, whether it be nucleus, cartilage, annular 鍖bers, etc, beyond the intervertebral disk space. This interspace is de鍖ned by the vertebral body endplates and ring apophyses, exclusive of os- teophytes. Localized displacement of disk can be categorized as focal or broad-based. It is usually best appreciated on axial imaging (Fig 7). However, the displacement of disk may occur in any plane. Visualization in all planes must occur to properly categorize herniations. Furthermore, disk herniations can be de鍖ned as protrusions vs extrusions. These are typically easily de鍖ned on sagittal images, but again, the de鍖nition must be applied in any plane. The base of the hernia is the widest part in a protrusion (Fig 8), whereas the herniated disk is wider than the base in an extrusion (Fig 9A-C). We provide an algorithm for analysis of disk displacement (Fig 10). Degeneration Degeneration is a broad description that can include changes seen with apparent desiccation (Fig 11) or 鍖brosis of disk, disk space narrowing, vacuum gas phenomena, diffuse generalized bulging disk, endplate sclerosis, and osteophytosis.1,2 When these changes occur, they can be subcategorized as spondylosis FIG 11. Degenerative change from disk desiccation. FIG 12. Spondylosis deformans. FIG 13. Intervertebral osteochondrosis. Curr Probl Diagn Radiol, May/June 2010 123
- 7. deformans2 (Fig 12), typically seen with aging, and/or intervertebral osteochondrosis2 (Fig 13), which is a more pronounced pathologic change within the disk. REFERENCES 1. Fardon DF, Milette PC. Nomenclature and classi鍖cation 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 Neu- roradiology. Spine 2001;26:E93-E113. 2. Grossman RI, Yousem DM. Neuroradiology: The Requisites, 2nd edition. St Louis, MO: Mosby, 2003. 3. Harnsberger HR, et al. Diagnostic and Surgical Imaging Anatomy: Brain, Head and Neck, Spine. Salt Lake City, UT: Amirsys, 2006. 124 Curr Probl Diagn Radiol, May/June 2010