eMedicine Specialties > Radiology > Musculoskeletal

Diffuse Idiopathic Skeletal Hyperostosis

Author: Khozaim Nakhoda, MD, MBBS, DRM, Director of Nuclear Medicine, Department of Radiology, Crozer Chester Medical Center
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
Contributor Information and Disclosures

Updated: Nov 2, 2007

Introduction

Background

Paraspinal 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:

• Forestier disease - The most common of the 3 syndromes, Forestier disease involves the anterior longitudinal ligament.
  • Forestier disease's more diffuse variant (which exhibits additional extra-axial features) is termed diffuse idiopathic skeletal hyperostosis (DISH)
• Ossification of the posterior longitudinal ligament (OPLL)

Pathophysiology

The etiology of DISH is uncertain. Glucose metabolism imbalance (diabetes), dyslipidemia, and hyperuricemia have been implicated.¹ DISH diagnostic criteria include the following² :

• Flowing calcifications and ossifications along the anterolateral aspect of at least 4 contiguous vertebral bodies, with or without osteophytes
• Preservation of disk height in the involved areas and an absence of excessive disk disease
• Absence of bony ankylosis of facet joints and absence of sacroiliac erosion, sclerosis, or bony fusion, although narrowing and sclerosis of facet joints are acceptable

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.

Frequency

United States

The incidence of DISH generally is believed to be 6-12% but is probably higher. In men older than 80 years, the incidence is 28%.

International

Although DISH occurs more commonly in Europeans and North Americans, OPLL occurs more frequently in the Japanese population.³

Mortality/Morbidity

• Most patients present with a stiff back, although nonspecific back pain may be associated with DISH. Rarely, kyphosis is present. Dysphagia occasionally is attributed to prominent osteophytes in the cervical spine.⁴
• Chronic pneumonia has been reported secondary to the obstruction of a bronchus. Fibrobullous changes have been reported, but they are probably secondary to the mechanical deformity of the thorax rather than to an intrinsic relationship (as found in ankylosing spondylitis).^5,6
• Hyperextension vertebral fractures and atlantoaxial subluxation have been reported.^7,8
• Stridor, nocturnal dyspnea, and vocal cord paralysis have been noted.^9,10
• Compression of the inferior vena cava has been attributed to DISH.¹¹
• Neurologic manifestations (secondary to spinal canal stenosis), heterotopic ossification, and metabolic causes (manifesting as paresthesia, gait disturbance, hyporeflexia) can be seen.^12,13
• Increased risk of heterotopic bone formation after hip surgery has been questioned.¹²
• Soft-tissue calcification, as in surgical scars, has been noted.¹⁴
• Association with hyperostosis frontalis interna and OPLL has been mentioned.¹⁵

Race

DISH 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

Sex

DISH occurs more commonly in males (65%) than in females (35%).²

Age

DISH occurs most often in persons aged 50-75 years.^2,17

Anatomy

The 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.

Presentation

Clinical 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 Examination

Radiography 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 Techniques

Radiography 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

Differential Diagnoses

Ankylosing Spondylitis
Neuropathic Arthropathy (Charcot Joint)
Osteoarthritis, Primary
Psoriatic Arthritis

Other Problems to Be Considered

Reiter syndrome, musculoskeletal

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