Reporting Lumbar Disk Abnormalities: At Last, Consensus!

Residents and fellows in musculoskeletal radiology or neuroradiology, who are trying to learn how to interpret imaging studies of the spine, are generally flabbergasted when they realize they will have to use a different terminology every time they review and report films with a different staff radiologist. They also find it somewhat weird that their mentors, whom they admire for their understanding of sophisticated MR physics, are incapable of explaining with a straight face how to differentiate a broad-based protrusion from an asymmetrical bulge. The answer to such annoying questions is likely to be: “Don't worry, this comes with experience!” Those who try to gain a better understanding of these concepts by browsing through textbooks or pulling out the relevant literature soon realize that no national or international consensus has ever been reached regarding comprehensive classification or standardized definitions of common lesions affecting intervertebral disks. A few schemes have been proposed by individuals, groups of authors, or nomenclature committees of professional associations, but none has been widely recognized as authoritative. This absence of consensus is greatly related to the multiple controversial aspects of disk abnormalities. Not only is there lack of general agreement regarding etiology, pathophysiology, validity of diagnostic procedures, clinical relevance of imaging findings, and, of course, treatment, but we are still uncertain about the biomechanics and even the anatomy of the intervertebral disk, especially in relation to spinal ligaments and membranes.

When the American Society of Spine Radiology (ASSR) was created in 1993, its founding members recognized the pressing need to deal with the lack of nomenclature standardization. Seventeen members enthusiastically volunteered to be part of the first ASSR ad hoc Nomenclature Committee and, in response to a preliminary survey, sent back to the chairperson so many conflicting opinions that efficient deliberations to reach a consensus appeared hopeless. In 1997, a smaller but well-balanced committee was formed, consisting of seven neuroradiologists from six different countries, with distinctive cultural backgrounds, perspectives, training, and, of course, inevitable biases. Rather than trying to devise a new system starting from scratch, it was agreed to scrutinize, modify, and improve previous work of a committee of the North American Spine Society (NASS), chaired by David Fardon, an orthopedic spine surgeon with extensive expertise in nomenclature and coding issues. Dr. Fardon graciously accepted to collaborate with us in this revision process, and formed a parallel clinical committee, including orthopedic surgeons, neurosurgeons, musculoskeletal radiologists, and one neurologist.

All participants in this revision process agreed to adhere to the following seven principles: 1) scope restricted to intervertebral disks and adjacent vertebral bodies; 2) focus limited to lumbar disks, although some concepts could eventually be extrapolated to other spinal segments; 3) use of the English language; 4) usefulness for interpretation of all types of imaging studies, and suitability for clinicians of various medical or surgical subspecialties; 5) simplicity, with the least possible number of categories, so that substantial interobserver agreement could be achieved; 6) consistency with macroscopic pathoanatomy: the postmortem study would be the optimal standard of reference to establish the validity of the model; and 7) freedom from legal and socioeconomic considerations, which are likely to differ anyway from state to state or from country to country.

After 20 months of tedious deliberations, mostly via e-mail, a consensus was reached at the level of the imaging and clinical task forces. The project then underwent an extensive revision process after being circulated to all ASSR members in order to get additional input. The document has since been presented to, and endorsed by, the NASS Board of Directors, the ASSR and ASNR Executive Committees, the American Association of Neurological Surgeons, and the Congress of Neurological Surgeons. It has also been approved by the CPT and ICD Coding Committee of the American Academy of Orthopaedic Surgeons. Endorsement by other North American, European, and international societies is currently pending. This work is being simultaneously posted on the website of the journal Spine, and on the ASSR and ASNR websites (www.asnr.org), owing to special arrangements concluded between the Editors and Publishers of Spine and the American Journal of Neuroradiology.

The length of this extensive document should not turn you off. The essential Recommendations actually hold in two pages referring to very simple illustrations. With hope, you will find the Discussion section worth reading, because it provides justification and explanations for the recommendations, as well as additional guidelines for detailed descriptions of disk herniations. Of course, the Glossary is not intended to be read from A to Z, but is provided as a quick reference tool for definitions of commonly used terms. And, by all means, skip the chapter on Coding if your practice does not require you to deal with this boring issue. The proposed classification and some of the preferred definitions will very likely disappoint some of you. Standardized terminology is essential to ensure uniformity and reliability in the collection, analysis, communication, storage, and retrieval of data; but terminology is established by way of convention, and consensus does not mean unanimity: some degree of compromise is expected from all who are involved. And consider the bright side: next time residents or fellows bug you with embarrassing questions on “bulging disks” or “protrusions”, referring them to this document will get you elegantly off the hook.