DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS (DISH)

The following is a case of Diffuse Idiopathic Skeletal Hyperostosis (DISH)

DISCUSSION :

• General Considerations




• More common in Caucasian males aged 50-75 years


• Ossification of anterior longitudinal ligament with or without osteophytes is the primary pathology


• DISH is an enthesopathy – there is reaction at the sites of tendinous insertions (entheses)


• Laminated, flowing ossification


• Should involve four contiguous vertebral bodies


• Ossification is usually quite thick


• Disc height is maintained in affected area


• Does not have ankylosis of SI joints




• Involvement of SI joints excludes DISH


• Involves lower thoracic spine most often, but also cervical and lower lumbar spine most frequently




• Left side of spine in thoracic area tends to not have ossification because of pulsations of aorta


• Clinical Findings




• Back stiffness or, less frequently, back pain




• Stiffness is worse in the morning


• Large osteophytes have also been reported to compress or obstruct a number of structures, including:




• Bronchus


• IVC


• Esophagus


• Increased incidence of calcification in surgical scars


• Associated with




• Hyperostosis frontalis interna


• Ossification of the posterior longitudinal ligament (OPLL)


• Ossification of the vertebral arch ligaments (OVAL)


• Imaging Findings




• Conventional radiography is usually study of choice


• Flowing ossification along anterior aspect of vertebral bodies, but separated from them and the body


• Should involve 4 levels


• Ossification may thicken as disease becomes more chronic


• “Whiskering” at the sites of tendinous insertion (entheses)




• Pelvic involvement




• Iliac crests


• Ischial tuberosities


• Iliolumbar ligaments


• Lesser trochanter


• Deltoid tuberosities of humerus


• Olecranon spurs


• Also may have ossification of the




• Achilles tendon


• Plantar aponeurosis


• Triceps tendon


• Differential Diagnosis




• Ankylosing Spondylitis




• Has involvement of SI joints


• Syndesmophytes are thinner


• Degenerative Disc Disease




• Osteophytes form only at corners of vertebral bodies


• Narrowing and desiccation of disc


• Acromegaly




• May produce osteophytes but they are not flowing


• Fluorosis may produce osteophytes, whiskering and ligamentous ossification




• But all bones are uniformly increased in density