Peh, WCG

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Title Radiological conference. Diffuse idiopathic skeletalhyperostosis (DISH)Author(s) Peh, WCGCitation Hong Kong Practitioner, 1997, v. 19 n. 5, p. 273-275Issued Date 1997URL http://hdl.handle.net/10722/44660Rights Creative Commons: Attribution 3.0 Hong Kong LicenseRADIOLOGICAL CONFERENCEClinical History:A 60-year-old man presented with a complaint of long-standing recurrent neck stiffness. There was no low backnor radiculopathic symptoms. Physical examination was normal except for mild l imita t ion of neck movements,particularly during flexion and extension. A cervical spine radiograph was taken (Figure 1).Figure 1: Lateral radiograph of the cervical spineWhat is the diagnosis?a) Ankylosing spondylitisb) Osteoarthritisc) Fluorosisd) Psoriatic spondyloarthritise) Diffuse idiopathic skeletal hyperostosisThis radiology case was prepared by: Dr. W.C.G. Peh, Associate Professor,Department of Diagnostic Radiology,The University of Hong Kong,Queen Mary Hospital.273Radiological ConferenceRADIOLOGICAL CONFERENCEAnswer: Discussione) Diffuse idiopathic skeletal hyperostosis (DISH)Radiological findingsFlowing ossification along the anterior aspects of C3to C7 vertebral bodies, corresponding to anteriorlongitudinal ligament ossification, is present. Theintervertebral disc heights are preserved and the facetjoints are intact. In addition, a dense linear band is seenposterior to C4 and upper half of C5 vertebral bodies,due to an ossified posterior longitudinal ligament (OPLL)(Figure 2).Figure 2: This figure is identical to Figure 1 withaddition of arrows. Flowing anteriorossification is seen linking C3 to C7vertebral bodies (white open arrows).Dense OPLL is arrowed (black arrows).Intervertebral disc spaces and facet jointsare normal. [3=C3 vertebral body; 6=C6vertebral body]a. Ankylosing spondylitisAnkylosing spondyli t is is a form of seronegativeinflammatory arthritis which affects the cartilaginousand synovial joints , and also manifests as anenthesopathy. It typically occurs in young men andis characterized by intermit tent back pain andprogressive stiffness. The i n i t i a l changes occur inthe sacro-iliac joints, followed by the thoracolumbarspine and lumbosacral regions, eventually progressingup the spine to involve the neck. Radiographically,extensive and symmetrical syndesmophytes bridgethe vertebral bodies, leading to the 'bamboo spine'appearance. The interspinous processes, facet jo in t sand costovertebral jo in t s are also even tua l l yankylosed.1-2 These c l i n i c a l and radiographicfeatures are not present in our patient.b) OsteoarthritisOsteoarthritis (or degenerative jo in t disease) isprobably the commonest form of arthri t isencountered radiologically. On radiographs, thehallmarks of Osteoarthritis are joint space narrowing,sclerosis and osteophytes. In the spine,osteophytes may arise as a result of shear stressesacross a degenerative disc. The tip of thesetraction-type osteophytes do not usua l ly protrudebeyond the horizontal plane of the vertebral end-plates.1-3 The orientation of the anterior cervicalossification, and lack of disc narrowing and sclerosisin our patient, excludes the diagnosis ofOsteoarthritis.c) FluorosisFluorosis results from long-term intake of largeamounts of fluorine. This is usually due to fluorinein drinking water in endemic areas, although it canalso be caused by therapy with sodium fluoride forosteoporosis. Radiographs show dense bone withcortex thickened at the expense of medul la , andcalcification of ligaments, tendons and interosseous274Hong Kong Practitioner 19 (5) May 1997RADIOLOGICAL CONFERENCEmembranes. Calcification of the sacrotuberousligament is considered to be characteristic offluorosis.1,3 This diagnosis can be discounted in ourpatient based on the history and radiographicfeatures.d) Psoriatic spondyloarthritisJo in t involvement in psoriasis occurs in 5% ofpatients and may antedate skin changes.Spondyloarthritis is one of five recognized clinico-radiological subtypes. In the spine, there isossification of the paravertebral connective tissuewhich, un l ike the syndesmophytes of ankylosingspondyli t is , is separated from the edge of thevertebral body and disc. This ossification is usuallylarge, coarse and asymmetrical. Bony ankylosis mayoccur. In the cervical spine, psoriasis may causeC1-C2 subluxation, mimicking rheumatoid arthritis.12None of these radiographic patterns are seen in ourcase.e) Diffuse idiopathic skeletal hyperostosis (DISH)DISH, also known as ankylosing hyperostosis orForestier's disease, is characterized by exuberantnew bone formation linking the vertebral bodies. Atleast 4 contiguous vertebrae should be affected forthis diagnosis to be considered. Ossification istypically located anterolaterally, causing undulatingossification of the anterior longitudinal ligament,outer fibres of the annulus fibrosis and theintervertebral disc itself. Ossified posteriorlongitudinal ligament (OPLL) is recognized to beassociated with DISH, occurring in 50% in oneseries.4 Un l ike ankylosing spondyl i t i s , the facetjoints and posterior elements are not affected, andthe sacro-iliac joints are normal. It is differentiatedfrom osteoarthritis by the absence of disc spacenarrowing and sclerosis.The cause of DISH is unknown, Postulatedaetiologies include altered vitamin A metabolism andlong-term ingestion of ret inoid derivatives. Itgenerally afflicts patients over the age of 50 years,being commonest in men.4 The condi t ion by itselfis usua l ly c l i n i ca l ly insignif icant . When OPLL ispresent in the cervical spine, the bony protrusionsmay encroach upon the oesophagus, giving rise todiscomfort during swallowing.2 Large OPLL mayalso compromise the spinal canal diameter andcompress the spinal cord, producing neurologicalsigns and symptoms.4 •ReferencesChapman S, Nakielny R. Aids to Radiological DifferentialDiagnosis. 3rd ed. Balliere Tindall. London. 1995; pp II,85, 521, 589.Forrester DM, Wesson JW. The Radiology of Joint Disease.W.B. Saunders, Philadelphia. 1973; pp 402-403, 409, 421-425 .Helms CA. Fundamentals of Skeletal Radiology. 2nd ed. W.B.Saunders, Philadelphia. 1995; pp 116-119, 160.Resnick D, Niwayama G. Diffuse idiopathic skeletalhyperostosis (DISH): ankylosing hyperostosis of Forestier andRotes-Querol. In: Resnick D. Diagnosis of Bone and JointDisorders. 3rd ed. W.B. Saunders, Philadelphia. 1995, pp1 4 6 3 - 1 4 9 5 .

Radiological conference. Diffuse idiopathic skeletal hyperostosis (DISH)

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Radiological conference. Diffuse idiopathic skeletal hyperostosis (DISH)

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