Diffuse idiopathic skeletal hyperostosis (DISH), also known as Forestier disease, is a common condition characterized by bony proliferation at sites of tendinous and ligamentous insertion of the spine affecting elderly individuals. On imaging, it is typically characterized by the flowing ossification of the anterior longitudinal ligament involving the thoracic spine and enthesopathy (e.g. at the iliac crest, ischial tuberosities, and greater trochanters). There is no involvement of the sacroiliac synovial joints. DISH is defined as flowing bridging anterior osteophytes spanning at least four vertebral levels, with normal disk spaces and sacroiliac joints
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Epidemiology
DISH most commonly affects the elderly, especially 6th to 7th decades 3. The estimated frequency in the elderly is ~10% 6, with a male predominance.
Associations
Recognized associations include:
ossification of the posterior longitudinal ligament, which may be a cause of spinal stenosis
hyperglycemia
approximately one-third of patients test positive for HLA-B27
Clinical presentation
The condition is commonly identified as an incidental finding when imaging for other reasons. However, spine stiffness and decreased mobility are referred to as possible symptoms.
Pathology
The etiology of DISH is still unknown. Histopathological features of spinal DISH include 5:
focal and diffuse calcification and ossification of the anterior longitudinal ligament
paraspinal connective tissue and annulus fibrosus
degeneration of the peripheral annulus fibrosus fibers
anterolateral extensions of fibrous tissue
hypervascularity
chronic inflammatory cellular infiltration
periosteal new bone formation on the anterior surface of the vertebral bodies
Location
The cervical and thoracic (particularly T7-11 5) spines, in particular, are affected. Additionally, enthesopathy may be identified in the pelvis and extremities.
Radiographic features
Plain radiograph and CT
Spinal features
flowing ossifications: florid, flowing ossification along the anterior or right 7 aspects of at least four contiguous vertebrae. The left lateral aspect is usually spared in the thoracolumbar spine, thought due to aortic pulsation inhibiting ossification 5. For the same reason, the right lateral aspect is spared in situs inversus 5.
disc spaces are usually well preserved
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ankylosis is more common in the thoracic than cervical or lumbar spine
frequently incomplete
can have interdigitating areas of protruding disc material in the flowing ossifications
no sacroiliitis or facet joint ankylosis although sacroiliac joint anterior bridging, posterior bridging, entheseal bridging may be present 10
Extraspinal features
enthesopathy of the iliac crest, ischial tuberosities, and greater trochanters
spur formation in the appendicular skeleton (olecranon, calcaneum, patellar ligament) frequently present
'whiskering' enthesophytes
Treatment and prognosis
DISH is generally managed clinically with analgesics and non-steroidal anti-inflammatory drugs when pain and stiffness are related. Possible complications may require specific treatment:
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acute spinal fractures in low impact trauma
inspect the ossified ligaments for disruption, and compare with prior imaging where available to discern fracture from a region without ossification
note that fractures can also occur above or below the rigid segment due to altered biomechanics
dysphagia is reported in ~28% of cases involving the cervical spine 12, which may be caused by mechanical compression due to anterior cervical bone production 8
cervical DISH can make intubation more difficult 11
lumbar DISH can cause radiculopathy 11
Differential diagnosis
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syndesmophytes: thinner, form over the annulus, and are vertically oriented ("bamboo spine")
sacroiliac joint involvement early on and is in the synovial portion (inferior two-thirds)
osteoporosis is prominent
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usually has prominent facet and apophyseal joints degenerative changes as well
disc degenerative changes
usually, the anterior longitudinal ligament of the thoracic spine is not affected 9
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patients using retinoid acid for skin diseases
skeletal hyperostosis
predominantly involves the cervical spine
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fluorite intoxication due to long-term ingestion
can cause paraspinal ligament calcification
if seen in a child, consider juvenile idiopathic arthritis (JIA)
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