bulge is defined as generalized mild extension of the outer boundary of the
intervertebral disc beyond the border of the adjacent bone. If there is not
other evidence of disc abnormality is may be considered a normal variant. Disc
volume and shape will adapt and change under different loading and positional
states. A symmetric disc bulge which involves between 50 and 100% of the
circumference of the disc is not considered a form of herniation and is more
likely to represent a normal state.
of Disc Disorders
important that physicians of various disciplines agree and understand the use
of common terminology to describe different disease processes. Standardization
of language or terminology is often a challenge. IN 1995 the North American
Spine Society (NASS) initiated efforts to standardize the use of terminology as
it applies to various disorders of the intervertebral disc. They received
assistance from the American Society of Spine Radiology (ASSR) and the American
Society of Neuroradiology (ASNR). The efforts lead to the development of
recommended classifications, definitions and criteria for different disc
disorders at various stages of development. The use of commonly accepted and
understood terminology helps physicians accurately communicate with their
patients and with each other. It influences the type of care recommended to
patients with spine disorders.
following disc disorder classifications and their descriptions are derived form
the nomenclature and classification of lumbar disc pathology, recommendations
of the combined task forces of the North American Spine Society, American
Society of Spine Radiology and American Society of Neuroradiology. These terms
describe what can be anatomically differentiated on imaging studies such as
MRI. Thus, this classification system is limited by the resolution capacity of
the imaging technology and may not accurately represent the actual anatomical
extent of the disc pathology.
disc: This term is
used to describe a young intervertebral disc that is structurally normal. This
term may be used to describe a mild diffuse disc bulge that does not show
evidence of any other abnormality.
with Congenital/Development Variation: This classification includes those discs which are
structurally abnormal as the result of hereditary considerations. This includes
disc that undergo structural (morphological) changes due to adaptation to
abnormal growth of the spine.
Disc Lesion: This
is a broad category which includes discs that present with degenerative
changes, evidence of traumatic compromise or a combination of both. This
category includes degenerative changes that may be age-related.
Disc Herniation: Disc herniation is defined as a localized displacement of disc material beyond the outer limits of the intervertebral disc. The material may consist of a portion of the gel-like nucleus, bone fragments, annular tissue or cartilage. A herniation may be further categorized as focal (< 25%of disc circumference) or broad based (between 25 and 50% of disc circumference). A herniated disc may present as a protrusion (contained herniation) or as an extrusion. An extrusion is associated with migration of disc material completely through the outer annular fibers of the disc. If a piece of the extrusion breakslose it is referred to as a sequestered fragment. If a disc herniation occurs into an adjacent vertebral body this is called an intravertebral herniation. Disc herniations are further classified as contained, uncontained, as well as by location, size, volume and content.
Disc Inflammation and Infection:This category of disc disorders includes infection,infection-like inflammatory changes and inflammation due to a variety of conditions. The presence of inflammatory changes in the disc is often referred to as discitis. Infectious and inflammatory changes often extend into neighboring bone (vertebrae).
cancer or metastatic cancer of disc tissues is referred to as disc neoplasia.
It is further categorized by the type of neoplasia.
Discs with Structural (Morphological) Variants of Unknown Significance: This category includes discs that
have structural abnormalities that cannot otherwise be classified into one or
more of the other accepted categories of disc disorders.
classification of lumbar disc disorders is:
(excluding age-related changes)
variant of unknown significance