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How’s Your Disk? Illustrative Glossaryof Degenerative Disk Lesions Using

Standardized Lexicon

SoHyun Boo, MD, and Jeffery P. Hogg, MD

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he growing demand for structured reporting in radiologyequires acceptance and familiarity of standard terms. Thisrticle clearly summarizes and illustrates the standard

exicon and classification scheme for degenerative lumbarisk pathology. First-year residents and veteran radiolo-ists will gain/refresh knowledge of the lexicon for stan-ard reporting. We provide an example-based illustratedlossary that contains diagrams and referenced descriptivexplanations to illustrate disk lesions in the current stan-ardized lexicon. Collected cross-sectional imaging of thepine from our tertiary care institution provides a clearatient-based representation of elements in the lexicon.

here is a myriad of descriptive terms for lumbar diskathology that has been historically used, some ofhich may overlap and cause confusion. More andore, there is a movement toward standardizing radi-

logy lexicon. This proves beneficial for the referringhysicians, other radiology colleagues, coding, andltimately, the patient. In 2001, the North Americanpine Society, along with the American Society ofpine radiology and the American Society of Neuro-adiology, agreed on and published guidelines forlassifying the different types of lumbar disk pathol-gy. This was also endorsed by the Joint Section onisorders of the Spine and Peripheral Nerves of themerican Association of Neurological Surgeons, theongress of Neurological Surgeons, and the Currentrocedural Terminology and International Classifica-

ion of Diseases Coding Committee of Americancademy of Orthopedic Surgeons.1 This educational

rom the Department of Radiology, WVU Health Sciences Center,organtown, WV.eprint requests: SoHyun Boo, MD, Robert C. Byrd Health Sciences Center,ox 9235 HSC, Morgantown, WV 26506. E-mail: sboo@hsc.wvu.edu.urr Probl Diagn Radiol 2010;39:118-124.2010 Mosby, Inc. All rights reserved.

363-0188/2010/$36.00 � 0

aoi:10.1067/j.cpradiol.2009.07.002

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rticle summarizes the standard nomenclature andlassification scheme (Table 1). Specifically, the clas-ification of degenerative/traumatic lesions has histor-cally been confounding in the numerous terms used.

systematic approach is offered to help guide thevaluation of the disk lesion with provided examples.

ormalorphologically, normal adult disks have a bilocular

IG 1. Normal bilocular appearing disk.

ABLE 1. Classification of disk lesions

NormalCongenital/developmental variantDegenerative/traumatic lesionInflammation/infectionNeoplasiaMorphologic variant of unknown significance

ppearance due to development of a central horizontal

Curr Probl Diagn Radiol, May/June 2010

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FIG 2. Schematic of normal disk considered as a 360-degree arc.

Fmorphologic change secondary to scoliosis in this case.

F(180°) of ring apophyses.

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Curr Probl Diagn Radiol, May/June 2010

and of fibrous tissue within the nucleus. “Normal”oes not give regard to the clinical context and doesot include aging, adaptive, developmental, or degen-

central canal zone

central zone (right or left)

or subarticular zone

nucleus pulposusannulus fibrosus

foraminal zone (pedicle zone)

extra-foraminal zone(far lateral zone)

IG 5. Normal disk consists of the nucleus pulposus and surroundingnnulus fibrosus. Disk hernias can be further described in its zonal

ocation.

IG 6. Annular tears are seen as high intensity nucleus pulposusxisting through areas of separation between the dark annular fibers.ntravertebral hernias are also seen.

ABLE 2. Subcategories of degenerative/traumatic lesions

Annular tear/fissureHerniation (extrusion/protrusion)Degeneration (desiccation, spondylosis deformans,

intervertebral osteochondrosis)

25%

90°

Normal disk

IG 3. Congenital developmental variant of disk which has undergone

Generalized disk bulge

25%

90° IG 4. Generalized disk bulge. Disk displacement involves �50%

rative changes, which may be clinically “normal”

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90°

Focal Hernia

25%

90°

Broad-based hernia

25%

IG 7. Localized displacement of disk can be a focal (�25%) or broad-based (25-50%) hernia.

90°

Protrusion

25%or

IG 8. Protrusion type hernia.

20 Curr Probl Diagn Radiol, May/June 2010

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Fig 1).1 The normal disk can be considered as a60-degree arc divided into 4 quadrants (Fig 2).1

ongenital Developmental Varianthese abnormal disks have undergone morphologichanges to adapt to abnormal growth of the spine suchs in scoliosis or spondylolisthesis (Fig 3).

There is generalized displacement of disk beyondhe endplates that constitutes a disk bulge. By conven-

90°

Extrusion

25%

or

IG 9. Extrusion type hernias.

ion, bulging disks involve �50% (180°) of the ring i

urr Probl Diagn Radiol, May/June 2010

pophyses (Fig 4).1 By this standard lexicon, a bulges not a hernia.

egenerative/Traumaticegenerative/traumatic change in the disk is a broad

ategory that again is purely descriptive and identifiesnd does not imply any relationship to the clinicalontext, pathology, or need for treatment. Severalubcategories of degenerative/traumatic lesions are

dentified in Table 2.

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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

ON SEY

YES YES NO NO

90°

Broad-based hernia 25%

90°

Focal hernia

25%

Generalized bulge

90°

IG 10. Algorithm for analysis of disk displacement.

22 Curr Probl Diagn Radiol, May/June 2010

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nnular Tearsnnular tears or fissures describe breaks or separationetween the dark annular fibers that extend concentri-ally, transversely, or radially, allowing the more highntensity nucleus to exit through (Figs 5 and 6).2,3

ntravertebral hernia is also seen in Fig 6.

isk Herniasy convention, a hernia is defined as localized dis-

IG 11. Degenerative change from disk desiccation.

IG 12. Spondylosis deformans.

lacement of disk material, whether it be nucleus, o

urr Probl Diagn Radiol, May/June 2010

artilage, annular fibers, etc, beyond the intervertebralisk space. This interspace is defined by the vertebralody endplates and ring apophyses, exclusive of os-eophytes.

Localized displacement of disk can be categorizeds focal or broad-based. It is usually best appreciatedn axial imaging (Fig 7). However, the displacementf disk may occur in any plane. Visualization in alllanes must occur to properly categorize herniations.

Furthermore, disk herniations can be defined asrotrusions vs extrusions. These are typically easilyefined on sagittal images, but again, the definitionust be applied in any plane. The base of the hernia is

he widest part in a protrusion (Fig 8), whereas theerniated disk is wider than the base in an extrusionFig 9A-C). We provide an algorithm for analysis ofisk displacement (Fig 10).

egenerationegeneration is a broad description that can include

hanges seen with apparent desiccation (Fig 11) orbrosis of disk, disk space narrowing, vacuum gashenomena, diffuse generalized bulging disk, endplateclerosis, and osteophytosis.1,2 When these changes

IG 13. Intervertebral osteochondrosis.

ccur, they can be subcategorized as spondylosis

123

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eformans2 (Fig 12), typically seen with aging, and/orntervertebral osteochondrosis2 (Fig 13), which is a

ore pronounced pathologic change within the disk.

REFERENCES. Fardon DF, Milette PC. Nomenclature and classification of

lumbar disc pathology: Recommendations of the Combined

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Task Forces of the North American Spine Society, AmericanSociety of Spine Radiology, and American Society of Neu-roradiology. Spine 2001;26:E93-E113.

. Grossman RI, Yousem DM. Neuroradiology: The Requisites,2nd edition. St Louis, MO: Mosby, 2003.

. Harnsberger HR, et al. Diagnostic and Surgical ImagingAnatomy: Brain, Head and Neck, Spine. Salt Lake City, UT:

Amirsys, 2006.

Curr Probl Diagn Radiol, May/June 2010