You are in: eMedicine Specialties > Radiology > MUSCULOSKELETAL Diffuse Idiopathic Skeletal HyperostosisArticle Last Updated: Nov 2, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 9
  Author: Khozaim Nakhoda, MD, MBBS, DRM, Director of Nuclear Medicine, Department of Radiology, Crozer Chester Medical Center Khozaim Nakhoda is a member of the following medical societies: American Roentgen Ray Society, Radiological Society of North America, and Society of Nuclear Medicine Coauthor(s): Gary Greene, MD, FACNM, Consulting Staff, Department of Medical Imaging, Medical Director, Division of Nuclear Medicine, Section Teaching Head of Orthopedic Radiology and Nuclear Medicine, Mercy Catholic Medical Center Editors: Leon Lenchik, MD, Director, Densitometry Minifellowship, Assistant Professor, Department of Radiology, Wake Forest University Medical Center; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; William R Reinus, MD, MBA, FACR, Professor of Radiology, Temple University; Chief of Musculoskeletal and Trauma Radiology, Vice Chair, Department of Radiology, Temple University Hospital; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington Author and Editor Disclosure Synonyms and related keywords: Forestier disease, Forestier's disease, DISH, ossification of the posterior longitudinal ligament, OPLL, anterior longitudinal ligament, posterior longitudinal ligament, ankylosing spondylitis, enthesopathy INTRODUCTIONSection 2 of 9
  BackgroundParaspinal ligaments undergo degeneration secondary to attrition, and they often ossify. This condition is broadly termed spinal enthesopathy. Physicians recognize the following syndromes as being associated with this phenomenon:
PathophysiologyThe etiology of DISH is uncertain. Glucose metabolism imbalance (diabetes), dyslipidemia, and hyperuricemia have been implicated.1 DISH diagnostic criteria include the following2:
Unlike ankylosing spondylitis, DISH does not involve the sacroiliac joint. DISH is also distinct from marginal osteophytes that form in response to degenerative disk disease. Patients with DISH infrequently demonstrate disk height reduction or vacuum changes. Lower thoracic spine involvement is typical of DISH, but the lumbar and cervical spine also can be affected. The left side of the spine typically is spared or less involved, which probably is attributable to the pulsating aorta. Forestier disease includes many extra-axial features, such as ossification of other ligaments and tendons, as well as subcutaneous calcification. FrequencyUnited StatesThe incidence of DISH generally is believed to be 6-12% but is probably higher. In men older than 80 years, the incidence is 28%. InternationalAlthough DISH occurs more commonly in Europeans and North Americans, OPLL occurs more frequently in the Japanese population.3 Mortality/Morbidity
RaceDISH occurs more commonly in whites persons than in black, Native American, and Asian populations. Although ankylosing spondylitis rarely occurs in the African black population, DISH is not uncommon, although its incidence is much lower than it is in the white population.16 SexDISH occurs more commonly in males (65%) than in females (35%).2 AgeDISH occurs most often in persons aged 50-75 years.2, 17 AnatomyThe vertebra consists of the anterior body and the posterior arch. The arch is composed of the paired pedicles, the laminae, the superior and inferior articular facets, and, posteriorly, the midline spinous process. Several ligaments extend across the vertebral column, providing stability. The anterior and posterior longitudinal ligaments run on the anterior and posterior surfaces of the vertebral bodies. The ligamentum flavum connects the laminae. The interspinous ligament extends between the spinous processes, while the supraspinous ligament extends between the tips of the spinous processes. Ossification of the anterior longitudinal ligament is the underlying pathology of Forestier disease and DISH. Clinical DetailsClinical symptoms include back stiffness with restricted motion. Complaints are intermittent; stiffness is worse in the morning and is relieved with mild activity. Symptoms are worsened when the patient sits for a length of time or when the weather is wet and cold. The lower thoracic area most commonly is involved. In the later stages, signs of spinal stenosis may be noted. (Also, see the Medscape article Pathogenesis, Presentation, and Treatment of Lumbar Spinal Stenosis Associated With Coronal or Sagittal Spinal Deformities.) Although advanced disease is the most common clinical feature in patients, various symptoms have been attributed to florid ossification, including dysphagia, stridor, chronic pneumonia, and vascular compression. Preferred ExaminationRadiography of the thoracic and lumbar spine usually is sufficient for diagnosing DISH. Occasionally, computed tomography (CT) scanning may be performed to evaluate complications, such as fracture, or symptoms caused by pressure effects on the trachea, esophagus, and veins. Bone scanning and magnetic resonance imaging (MRI) do not play a significant role in the diagnosis of DISH. Limitations of TechniquesRadiography of the spine is the single most useful imaging modality in the diagnosis of DISH. However, patient body habitus or an inability of the patient to lie on his or her side for a lateral view may compromise the quality of radiographs. In addition, radiographs are inadequate for evaluating the extent of the compression caused by the large syndesmophytes on the trachea, bronchi, or esophagus. In this case, CT scanning of the spine is helpful and especially is aided by coronal and sagittal reconstructions. Conversely, CT scanning usually is not cost-effective for imaging the entire spine and provides limited information about spinal cord involvement. In this situation, MRI is of benefit and thus is reserved primarily for evaluating possible cord compression. This is especially true if DISH is associated with OPLL, as it is in a minority of patients.2 DIFFERENTIALSSection 3 of 9
Ankylosing Spondylitis Neuropathic Arthropathy (Charcot Joint) Osteoarthritis, Primary Psoriatic Arthritis Other Problems to Be ConsideredReiter syndrome, musculoskeletal RADIOGRAPHSection 4 of 9
FindingsRadiographs of the spine typically demonstrate thoracic spinal involvement; however, DISH can also affect the lumbar and cervical spine. DISH is distinguished by the presence of flowing syndesmophytes along, but separated from, the anterior aspect of the vertebral bodies, involving at least 4 levels. The disease begins as fine ossification, 1- to 2-mm thick, but ossification may thicken to as much as 20 mm as the disease progresses. Radiographic findings in DISH include the following extra-axial features:
Degree of ConfidenceThe hallmark of DISH is ossification occurring along the anterior aspect of the vertebral bodies but remaining separate from the vertebrae. Osteophytes of degenerative spinal disease usually occur along the anterolateral aspect. The location of the ossification distinguishes DISH from OPLL. False Positives/NegativesOmnipresent degenerative osteophytes represent the most common finding that mimics DISH; however, DISH is defined by the strict criteria of anterior location and the bridging involvement of 4 contiguous vertebral bodies (3 intervertebral disk spaces). CT SCANSection 5 of 9
FindingsCT scanning usually is not indicated unless there is a need to evaluate complications, such as fracture, spinal canal stenosis secondary to associated OPLL, and pressure effects on the esophagus or inferior vena cava. CT scans show ossification along the anterior aspect, and coronal reconstruction depicts the classic pattern. Degree of ConfidenceThe same criteria used in radiographic evaluation (the location of the ossification and an involvement over at least 4 vertebral bodies) define DISH and distinguishes this entity from degenerative osteophytes. MRISection 6 of 9
FindingsMRI of the spine usually is not indicated, because diagnosis is made using plain radiographic findings. CT scanning, using coronal and sagittal reconstruction, is useful because it provides better anatomic definition. When associated OPLL causes neurologic symptoms, MRI is valuable for determining the extent of the ossification, the mass effect on the thecal sac, and the presence of cord compression. Typically, DISH manifests as a long segment of low T1 and T2 signals that is anterior to several contiguous vertebrae, while OPLL manifests as a signal that is posterior to the vertebral body and that extends for several segments. Cord edema manifests as a high T2 signal. NUCLEAR MEDICINESection 7 of 9
FindingsIn nuclear medicine, bone scanning usually is requested for the evaluation of back pain, revealing the nonspecific pattern of the diffusely increased and heterogeneous uptake of radiopharmaceutical in the spine. Diagnosis relies primarily on the use of radiographs. Degree of ConfidenceThe appearance of DISH on a bone scan is nonspecific, and without radiographic correlation, diagnosis is difficult. MULTIMEDIASection 8 of 9
REFERENCESSection 9 of 9
Diffuse Idiopathic Skeletal Hyperostosis excerpt Article Last Updated: Nov 2, 2007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
