AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Background

Diffuse idiopathic skeletal hyperostosis (DISH) describes a phenomenon characterized by a tendency toward ossification of ligaments. It most characteristically affects the spine. Ossification of the longitudinal ligaments (especially the anterior ligaments) of the spine produces a tortuous paravertebral mass anterior to and distinct (at least radiologically) from the vertebral bodies. Grossly, the appearance is that of candle wax dripping down the spine. While the thoracic anterior longitudinal ligament is ossified, the areas of ossification often meet without fusion. Motion actually is possible, in contrast to lumbar vertebral bridging, which is associated with loss of lumbar motion. The zygapophyseal and sacroiliac joints are not involved in DISH, and the intervening intervertebral disk space is preserved.

DISH is well represented in the zoologic and paleontologic record. It is found in 1-3% of baboons and monkeys, as well as in gorillas, bears, camels, horses, bison, musk oxen, canids, felids, and whales; DISH was also present in dinosaurs (Rothschild, 1987). An age-dependent phenomenon, it occurs in 15-25% of older mammals.

Pathophysiology

DISH is characterized by a tendency toward ossification of ligament, tendon, and joint capsule (enthesial) insertions. DISH is a completely asymptomatic phenomenon; no alterations are detectable based on history or through physical examination.

Frequency

United States

DISH is present in approximately 19% of men and 4% of women older than 50 years. Frequency information in the US was derived from the study of nonselected skeletal/cemetery populations (Rothschild, 1985).

International

The posterior longitudinal ligament of the cervical spine is ossified in 2% of Japanese individuals but in only 0.16% of white persons. The anterior longitudinal ligament is calcified in 24% of patients with posterior longitudinal ligament ossification (Tsuyama, 1984).

Mortality/Morbidity

DISH appears to be a phenomenon rather than a disease. Double-blind controlled evaluation (in which controls and patients were drawn from the same population) revealed no associated pathology. Arthritis, bursitis, and tendinitis appeared no more frequently in patients with DISH than in controls. Any back pain present was no different in character or duration than that noted in control subjects. A history of back injury was actually found to be twice as frequent in control subjects as it was in patients with DISH. Back flexibility was no more limited in patients with DISH than it was in controls. In fact, patients with DISH who had decreased lumbar spinal motion had a lower frequency of back pain, implying that DISH may be protective (Rothschild, 1985; Schlapbach et al, 1989).

Race

The posterior longitudinal ligament of the cervical spine is ossified in 2% of Japanese individuals but in only 0.16% of whites.

Sex

DISH is present in approximately 19% of men older than 50 years but is found in only 4% of women in this age group.

Age

DISH is uncommon in patients younger than 50 years and is extremely rare in patients younger than 40 years.

• A study from Finland revealed the age frequency in Finnish men to be as follows (Julkunen et al, 1981):
  • 40-49 years - 0.3%
  • 50-59 years - 2.7%
  • 60-69 years - 8.4%
  • 70 years or older - 11.2%
• The same study revealed the age frequency in Finnish women to be as follows:
  • 40-49 years - 0.2%
  • 50-59 years - 1.7%
  • 60-69 years - 4.3%
  • 70 years or older - 6.9%

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

History

DISH is an asymptomatic phenomenon. The condition is discovered inadvertently. Rarely, dysphagia may result, either from neuropathy or from physical impingement by bony overgrowth.

Physical

If vertebral fusion is quite extensive, reduction in range of spinal motion occurs. Because uniform vertebral involvement is extremely rare, no relatable findings exist.

Causes

Causes are unknown. DISH is simply a tendency toward calcification of entheses.

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Spondylosis deformans
Fluorosis
Osteomalacia
Acromegaly
Hypervitaminosis A
Retinoids
Pachydermoperiostosis
Hypophosphatemia
Hypoparathyroidism
Ossified posterior longitudinal ligament (OPLL)

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Lab Studies

• No laboratory tests are indicated. An apparent association with elevated glucose levels has not been substantiated as a relationship with diabetes.

Imaging Studies

• Thoracic vertebrae are involved in 100% of affected individuals, lumbar vertebrae in 68-90% of these persons, and cervical vertebrae in 65-78% of affected individuals. Ligamentous ossification affects both sides of the lumbar vertebral column but tends to be unilateral in the human spine. Prominence of DISH on the right lateral aspect of the thoracic spine is apparently related to aortic pulsations. Left-sided overgrowth is much reduced, also probably because of the influence of aortic pulsations, an idea supported by the notation of left-sided prominence in individuals with situs inversus (left-sided thoracic aorta).
• The earliest sign of DISH appears to be new bone formation adjacent to the midportion of the vertebral body, a phenomenon often below the limits of radiologic detection. Recognition of DISH is facilitated by its separation from the body of the vertebrae. This gives rise radiologically to the appearance of a radiodense line paralleling the longitudinal axis of the spine but separated by a clearly definable space.
• The general term DISH emphasizes that the ligamentous ossification phenomenon is not limited to the spine. Exuberant ossification at sites of tendon, ligamentous, or joint capsule insertion (enthesitis) is strongly suggestive of the diagnosis. A tendency toward such ossification at any site of ligament and perhaps tendon insertion appears to exist. Enthesial reaction at the iliac crest and ischial tuberosities often is referred to as pelvic whiskering and typically is quite exuberant. Such whiskering was noted in two thirds of iliac crests studied and in 53% of ischial tuberosities. Enthesial reaction was noted in 42% of lesser and 36% of greater trochanters of the femur. Enthesial spurs at the site of insertion of the quadriceps mechanism into the patella were present in 29% of patients studied. Osseous bridging of fibula and tibia was noted in 10% of patients. Distal metacarpal and phalangeal capsular hyperostosis were present in 13% of patients with DISH (Rothschild, 1985).

Histologic Findings

Ossified tissues in DISH are composed of normal-appearing haversian bone as opposed to the wormian or disorganized structure of bone seen in patients with hypervitaminosis A.

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical Care

No medical care is indicated (see Introduction, Mortality/Morbidity).

FOLLOW-UP

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Complications

• Overgrowth of ligamentous calcification could impinge on other structures (eg, the esophagus). Reports of this are rare and often represent inadvertently discovered, neurologically mediated swallowing deficits.
• Posterior longitudinal ligament ossifications may impinge on the spinal cord on rare occasions.
• Reduced vertebral column flexibility predisposes to vertebral fracture.

Prognosis

• The prognosis is excellent, as DISH is not a source of morbidity or mortality.

MISCELLANEOUS

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• The major pitfall is mistakenly attributing back complaints to DISH rather than investigating for the true cause.
• Failing to observe resorption of preexisting DISH due to pulsating abrasion by an aortic aneurysm is another potential pitfall.

Special Concerns

• Resorption of preexisting DISH suggests the presence of an aortic aneurysm.

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

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Article Last Updated: Mar 2, 2007