Diffuse Idiopathic Skeletal Hyperostosis: The Spine Stiffness

Introduction

Diffuse idiopathic skeletal hyperostosis (DISH), which is also known as Forestier's disease, is a systemic disorder characterized by idiopathic calcification of the ligaments and tendons at spinal and peripheral entheses. DISH presents itself as pain in the spine, knee, shoulder, elbow, or calcaneus.

Who Is Susceptible to Diffuse Idiopathic Skeletal Hyperostosis?

DISH usually affects the population over 50 years, with the highest prevalence between 60 to 80 years of age. An estimated 10 to 12 % of older age individuals suffer from DISH symptoms. The condition shows a male predilection. Over 50 years of age, DISH is observed in 25 % of the males and 15 % of the females, which increases to 28 % and 26 %, respectively, in the 80+ aged individuals.

The conditions set between the 3rd and 5th-decade then manifests later in life. DISH may be more prevalent in the white population over the black, Asian, and Native-American populations.

An autopsy study revealed a mean age of 65 years with a prevalence rate between 2.5 % and 28 %. In a Japanese study, the prevalence was 17.6 % and 27.2 %, as observed on CT (computed tomography) and X-ray alone, respectively.

What Causes Diffuse Idiopathic Skeletal Hyperostosis?

DISH has been studied to be associated with several systemic metabolic disorders like diabetes mellitus, hyperinsulinemia (too much insulin in the blood), obesity, dyslipidemia (lipid imbalance), and hyperuricemia (increased uric acid in the blood). The contributing factors arising from these predisposing conditions, mechanical stress and strain patterns, exposure to various toxic factors, and genetic contribution have been hypothesized to form the etiology of DISH. Predisposing atherosclerosis and aortic valve sclerosis increase the risk of DISH and progressively predict the cause of future cardiovascular events.

What Is the Pathophysiology of Diffuse Idiopathic Skeletal Hyperostosis?

DISH is most commonly seen in the rise half of the thoracic region but seldom occurs on the contralateral side (left thoracic region). This stark contrast is due to the protective effect, and mechanical barrier produced secondary to the pulsatile descending aorta. It is observed that in cases of situs inversus (mirrored placement of organs in contrast to their natural position), ossification is seen on the left half of the thoracic region, which supports the pulsatile aorta theory.

The pattern of ossification is evidently different in the cervical and lumbar regions. The ossification is anterior to vertebral bodies in the cervical and lumbar region, which is in disparity with the anterolateral pattern in the thoracic region. A plausible explanation for this difference is the regional arterial morphology.

But both regions have shown similar symmetrical non-marginal syndesmophyte ossification patterns. These bony growths, along with nerve impingement, can cause pain, and such abnormalities can lead to acute monoarticular synovitis (inflammation of a single joint), reduced spinal movement, dysphagia, polyarticular arthralgia, pain in the spine or the limbs; and an increased risk of unstable spine fractures.

What Are the Signs and Symptoms of Diffuse Idiopathic Skeletal Hyperostosis?

The initial period pertaining to DISH may be fairly asymptomatic, and the condition may be discovered incidentally.

Manifestations of DISH include

• Neck and appendage stiffness.

• Pain.

• Loss of range of motion.

• Difficulty in swallowing.

• Hoarseness of voice.

• Numbness.

• A tingling sensation in the legs.

• Possible paralysis.

• Enlarged bony ridges in the C/T/L-spinal vertebrae.

• New bony growths.

• Sleep apnea.

• Difficult intubation.

• Longer lever arm throughout the spine.

• Heel spurs.

• Achilles tendinitis.

• Plantar fasciitis.

• Ossification in iliac wing and ischial tuberosity.

• Other sites of ossification: hip, knee, shoulder, elbow, hand, and wrist.

How to Diagnose Diffuse Idiopathic Skeletal Hyperostosis?

The clinical diagnosis is based on the traditional diagnostic criteria that enunciate the fulfillment of three observations:

• Ossification of four or more vertebrae.

• Unchanged vertebral disc height and lack of degeneration of the vertebrae (in contrast to degenerative spondylosis).

• Absence of ankylosis between vertebrae and lack of erosion, sclerosis, or fusion at the pelvic joint in contrast to ankylosing spondylitis.

The modified latest diagnostic criteria suggest the fulfillment of just two findings:

• Presence of new bone formation in the spinal segments.

• Enlarged bony bridges C, T, or L-spine.

What Are the Radiographic Findings of Diffuse Idiopathic Skeletal Hyperostosis?

Radiographs of the spine in a lateral orientation demonstrate a “flowing candle wax” pattern which denotes non-marginal syndesmophytes projecting horizontally to the vertebrae and forming extra-articular ankylosis.

Ordering thoracic spine or chest radiographs in patients with primary neck or low back pain, stiffness, and diffuse extremity complaints can help in the early diagnosis of DISH. Technetium bone scan in DISH reveals increased uptake of contrast dye in the affected regions, similar to the presence of metastatic disease. So, additional X-ray studies would be required. Occults of recurrent fractures in patients should be evaluated using advanced imaging techniques like CT (computed tomography), MRI (magnetic resonance imaging), or CT myelogram.

Laboratory tests like ESR (erythrocyte sedimentation rate), CRP (c-reactive protein test), ANA (antinuclear antibody test), and Rh-factor are of little importance as they tend to be within the normal range.

How to Differentiate DISH from Ankylosing Spondylitis?

DISH can be clinically differentiated from ankylosing spondylitis by detecting subtle differences like

• Age of presentation: DISH presents at a high age.

• Sacroiliac joint erosion is absent in DISH.

• Absence of apophyseal joint obliteration in DISH.

• Ossification of the anterior longitudinal ligament.

• Enthesopathy with erosions is absent in DISH.

• No association with HLA-B27 in DISH.

• Clinical symptoms are milder in DISH.

• Pain is milder in DISH.

• DISH is discovered incidentally in asymptomatic patients.

How to Treat or Manage Diffuse Idiopathic Skeletal Hyperostosis?

• The treatment protocol against DISH involves the management of pain and underlying predisposing disorder and corrective measures against pathological growths.

• Home remedies involve using heat pads to reduce pain. Pharmacotherapy involves the usage of NSAIDs and corticosteroids.

• Physical therapy, activity modification, and exercise can improve joint mobility, and the use of braces to relieve pressure on the joint. Surgical interventions, decompression, and stabilization may be essential in case of fracture, cervical myelopathy, lumbar stenosis, neurologic deficits, infection, or painful deformity.

What Are the Differential Diagnosis of Diffuse Idiopathic Skeletal Hyperostosis?

• Ankylosing spondylitis (bone inflammation that may cause spinal fusion).

• Spondylosis deformans (degenerating vertebral discs).

• Seronegative spondyloarthropathies (a group of various arthritic conditions).

• Charcot's spine (progressive neuropathic vertebral joint degeneration).

• Acromegaly (excess production of growth hormone).

• Psoriasis (autoimmune skin disorder).

• Reactive arthritis (joint inflammation triggered by a distant infection).

• Pseudogout (calcium pyrophosphate deposition disease).

• Hypoparathyroidism (deficient parathyroid hormone).

• Degenerative spine disease (intervertebral disc degeneration).

• Retinoid arthropathy (pelvic hyperostosis and ossification of the anterior longitudinal ligament).

• Fluorosis (excessive fluoride intake causing skeletal and dental changes).

• Juvenile idiopathic arthritis (early age arthritis).

What Is the Prognosis of Diffuse Idiopathic Skeletal Hyperostosis?

DISH typically presents with a good prognosis. People suffering from DISH usually have a good life expectancy after managing the underlying condition. Delayed or lack thereof treatment leads to major complications ranging from chronic pain to paralysis.

What Are the Complications of Diffuse Idiopathic Skeletal Hyperostosis?

• Spinal fractures.

• Heterotopic ossification following total hip arthroplasty.

• Paralysis.

• Permanent disability.

Conclusion

DISH occurs in older individuals, who often have predisposing age-related pathologies. The symptoms are often disregarded owing to the age and are mostly diagnosed incidentally on health check-ups pertaining to some other condition. Upon diagnosis, the proper protocol should be inculcated to prevent further damage and complications. The regime should include emergency medical services providers, nurses, advanced practitioners, clinicians, and surgeons to manage the condition in this fragile age. The patients and their family members must be educated regarding the condition, the risk of fractures, even with minor trauma, and the steps to be taken in case of an emergency.