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Diffuse idiopathic skeletal hyperostosis (DISH), or Forestier disease, is a fairly common (up to 28% of elderly patients) degenerative disorder of unknown etiology, affecting mostly older patients (45 to 85 years old) and men (65%) more than women. It was first described in 1950 as a disorder characterized by spinal stiffness, osteophytosis, and “flowing” new bone formation along the margins of the thoracic spine (Fig. 26.1A). The anterior longitudinal ligament (ALL) is usually most involved. Although the disease is more prevalent in certain families, no clear genetic association with the human leukocyte antigen (HLA) system has been identified, and no relationships have been found with either rheumatoid arthritis or ankylosing spondylitis (AS), with which it is often confused. DISH can be associated with type II diabetes, obesity, biliary stones, atheromatous vascular disorders, hypertension, and lipid and purine metabolism disorders.

Classification

DISH is characterized by ossification of the ligamentous insertions (fibro-osteosis) and ossification/calcification of tendons, ligaments, and fascia in both the axial and the appendicular skeleton. This is caused by invasion of blood vessels into cartilage and differentiation of pluripotent cells into osteoblasts. The most common symptoms of DISH are spinal rigidity and decreased joint mobility with occasional dysphagia from esophagus compression (Fig. 26.1B). Pain and nerve root irritation due to narrowing of the vertebral foramina rarely occur, but spinal cord compression secondary to ossification of the posterior longitudinal ligament (OPLL; see Chapter 22) can cause myelopathy. The diagnostic criteria for DISH include (1) flowing ossifications along the anterolateral aspect of at least four thoracic vertebrae, (2) absence of (Fig. 26.1A) facet-joint ankylosis or sacroiliac sclerosis (these criteria belong to AS; see Chapter 25), and (3) conservation of intervertebral disk height between involved segments.

The T7 to T11 levels are most frequently involved, and the changes are often visible even on a chest radiograph. Extraarticular ankyloses take the form of flowing candle wax in DISH, as opposed to the vertically oriented osteophytes in the “bamboo spine” that form intraarticular ankyloses in AS (see Chapter 25). Disk space narrowing is minimal, and the facet joints are usually preserved. A bone scan generally shows increased uptake and can raise the suspicion of a malignancy. Axial computed tomography (CT) cuts show a thin radiotransparent band between the calcified ALL and the vertebral body wall on the right side of the anterior spine.

Treatment

Patients suffering from DISH are at high risk for spinal fractures. Delayed diagnosis is frequent because the trauma is often trivial. Hyperextension injuries occur most frequently through an entire vertebral body or through a disk space in between the ankylosed segments; the incidence of neurologic compromise is relatively high. The long lever arm that develops as a consequence of the ankylosis of multiple vertebral elements causes fractures to displace easily. Back and neck pain after minor trauma in a patient with DISH need to be worked up with a high index of suspicion for fracture. Involved areas need to be imaged (Fig. 26.2A,B) with either CT or magnetic resonance imaging (MRI) to rule out global spinal instability, because this is usually underrepresented on plain radiographs.

Related posts:

Odontoid Fractures Cervical Disk Degeneration Lumbar Degenerative Spondylolisthesis Post-Traumatic Thoracolumbar Kyphosis Spinal Imaging for Pseudarthrosis Posterior Lumbar Non-Fusion Devices

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