M u s c u l o s k e l e t a l I m a g i n g • P i c t o r i a l E s s ay Spira et al. MRI of Psoriatic Arthritis

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Musculoskeletal Imaging Pictorial Essay

MRI Findings in Psoriatic Arthritis of the Hands Daniel Spira1 Ina Kötter 2 Jörg Henes 2 Jasmin Kümmerle-Deschner 3 Maximilian Schulze1 Andreas Boss1 Marius Horger 1 Spira D, Kötter I, Henes J, et al.

Keywords: arterial spin labeling, dynamic contrastenhanced MRI, enthesitis, juvenile psoriatic arthritis, MRI, psoriatic arthritis, tenosynovitis DOI:10.2214/AJR.10.4281 Received January 15, 2010; accepted after revision April 12, 2010. 1 Department of Diagnostic Radiology, Eberhard-KarlsUniversity, Hoppe-Seyler-Straße 3, 72076 Tübingen, Germany. Address correspondence to M. Horger ([email protected]). 2 Department of Internal Medicine–Oncology, Eberhard-Karls-University, Tübingen, Germany. 3 Department of Pediatric Rheumatology, Eberhard-KarlsUniversity, Tübingen, Germany.

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OBJECTIVE. The purpose of this essay is to provide a practical review of the spectrum of morphologic and functional MRI findings in psoriatic arthritis of the hand joints. CONCLUSION. The MRI findings of psoriatic arthritis include enthesitis, bone marrow edema, and periostitis accompanying articular or flexor tendon sheath synovitis in the early stage accompanied by destructive and proliferative bony changes, subluxation, and ankylosis in the late stage.

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ccording to the classification criteria for psoriatic arthritis [1], the prevalence of clinically evident psoriatic arthritis in persons with psoriasis is estimated at less than 13.8%. Current data, however, support the notion that psoriatic arthritis is underdiagnosed owing to a high incidence of subclinical disease [2]. The pathogenesis of psoriatic arthritis is not resolved. McGonagle et al. [3] hypothesized the existence of a synovioenthetic complex unifying joint and bursal synovium with the insertions of neighboring tendons, ligaments, and muscles as one conjoint organ. In this respect psoriatic arthritis is regarded primarily as synovioenthesitis that induces inflammation in adjacent tissues owing to diffusion of cytokines [3]. Skin involvement is the common denominator of psoriatic arthritis, preceding joint symptoms in approximately 80% of cases, although 15% of patients experience arthritic symptoms first [4]. Psoriatic arthritis encompasses a spectrum of subgroups. According to the Moll and Wright criteria [5], it is classified into five clinical varieties, four of these involving the small joints of the hands and feet: polyarthritis of the distal interphalangeal joints, monoarthritis or asymmetric oligoarthritis, mutilating arthritis with ankylosis and joint deformity, and symmetric seronegative polyarthritis simulating rheumatoid arthritis. The hand is the most frequent location of psoriatic arthritis, being involved in approximately 40% of patients. Knowledge of the clinical and radiologic appearance is mandatory for appropriate diagnosis. Owing to immediate availability and low cost, conventional radiog-

raphy is the primary imaging technique in suspected arthritis. MRI, however, allows much more sensitive and detailed assessment of anatomic and functional joint status. The main benefit of MRI over radiography in the workup of psoriatic arthritis consists in its utility in visualization and quantification of the activity of inflammation and its higher sensitivity in the detection of associated soft-tissue and bone changes. Thus the diagnosis can be made and treatment begun long before irreversible damage (e.g., bone destruction, ankylosis) has occurred. Nevertheless, imaging of a patient with any type of arthritis should always start with radiographs. MRI is used to verify, exclude, or classify disease in ambiguous cases. Accompanied by a year’s evidence of the typical radiographic changes of psoriatic arthritis, the MRI data are used for differentiation of psoriatic arthritis from other types of arthritis. Anatomic MRI of Small-Joint Psoriatic Arthritis The basic MRI protocols used in imaging of patients with psoriatic arthritis should include T1-weighted acquisition in both the long and short axes of the hand and T2- and T1-weighted gadolinium-enhanced sequences in either the long or the short axis of the hand with surface or dedicated hand coils. If possible, imaging should be performed at high field strength for an optimal signal-to-noise ratio. The focus should be on the symptomatic joints. The two main clinical goals in psoriatic arthritis—early diagnosis and correct classification before treatment—rely on MRI, as does evaluation of therapeutic response in the later stages of arthritis.

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Spira et al. Unlike rheumatoid arthritis, which has a polyarticular presentation, early psoriatic arthritis can occur in any of the small hand joints, mostly as monoarthritis or oligoarthritis (Fig. 1). Two types of involvement of the hand and foot suggest the presence of psoriatic arthritis: the row pattern, primarily, which affects the distal interphalangeal joints, and the ray pattern, which is mainly confined to the tendon sheath synovia. Differentiation between the former type and joint degeneration (arthrosis) can be challenging, particularly in the care of older patients, who have an overlap of the two disorders. The ray pattern also occurs in reactive arthritis, but the occurrence and clinical course of these two disorders allow reliable discrimination. Isolated tenosynovitis, especially of the flexor tendon sheaths, with additional synovitis or soft-tissue edema results in dactylitis, or sausage digits, which is a hallmark of psoriatic arthritis, often representing the first clinical manifestation (Figs. 2 and 3). Flexor tenosynovitis is a common finding, whereas extensor tenosynovitis is observed less frequently (Figs. 4 and 5). Several fingers can be involved simultaneously (polydactylitis). Differentiation of tenosynovitis from articular synovitis can be clinically challenging, especially when the inflamed synovial membrane of the tendon sheath abuts the articular synovial membrane of the metacarpophalangeal joints or proximal interphalangeal joints. Tender dactylitis is associated with a more aggressive disease course, reflected, among other characteristics, by more frequent bone marrow edema than in nontender dactylitis [6]. Despite subtle differences in the histopathologic features of inflamed synovial membranes, at MRI the morphologic findings and degree of synovitis in psoriatic arthritis appear indistinguishable from those of rheumatoid arthritis; both exhibit nonspecific contrast enhancement of the synovial membrane [7] (Fig. 6). Pronounced periarticular osteoporosis is not seen in psoriatic arthritis as it is in rheumatoid and septic arthritis. However, early extracapsular enhancement with diffuse and in some cases pronounced soft-tissue edema spreading to the subcutis is typical of psoriatic arthritis [8] (Fig. 6). Inflammation of the periosteum is part of the spectrum of enthesitis and is well illustrated on MR images as contrast enhancement directly alongside the diaphysis (Fig. 7A). Such periostitis leads to adjacent cortical bone proliferation, which can at later stages impress as irregular or smooth cortical thickening, a characteristic finding in psoriatic arthritis [9]. Bone marrow edema is usually ill-defined with in-

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tact overlying cortical bone (Fig. 7B). In psoriatic arthritis, bone marrow edema begins at the corner of the phalanx at the insertion of the capsule and spreads to involve the entire bone as the disease progresses (Fig. 8). Infliximab treatment results in dramatic short-term improvement of MRI-determined bone marrow edema in psoriatic arthritis [10]. Perienthetic edema and hyperemia accompany bone marrow edema and periarticular erosions as part of synovioenthesitis (Fig. 8). Muscular fascial thickening also occurs with extracapsular inflammation (Fig. 9). Collateral ligament and volar plate enhancement and extensor tenosynovitis are less common findings also found in rheumatoid arthritis. More advanced psoriatic arthritis (late psoriatic arthritis) attacks joints and entheses aggressively, disrupting the bone cortex with underlying inflammatory changes in the cancellous bone. Such erosions are suggestive of small junks bitten out of the main bone and are well visualized with MRI (Fig. 10). Unlike in rheumatoid arthritis, bone marrow edema does not seem predictive of the development of erosions in patients with rheumatoid arthritis [8]. However, erosions also begin at the lateral aspects of the joint regions (bare areas) and progress to more central areas later in the disease course. Thus the involved phalanges seem to taper. Advanced joint destruction ultimately results in joint deformations such as pencil-andcup deformity and complete bone fragmentation resembling neuropathic osteoarthropathy (Fig. 11A). Subluxation and ankylosis also are characteristic of end-stage psoriatic arthritis (Fig. 11B). A distinctive feature with disease progression is subchondral sclerosis by reactive bone growth (Fig. 12A). Bone proliferation is not restricted to joints but also involves periarticular and subperiosteal locations that are not eroded, most notably in areas where ligaments, tendons, and muscles insert into bone. This osteoproliferation (eburnation) results in reduced or voided signal on both T1- and T2-weighted images owing to immobilization of protons (Fig. 12B). MRI evidence of nail involvement, such as nail thickening and surface irregularity, is visualized in almost all patients with psoriasis, even if onychopathy is not clinically apparent. These findings become relevant in patients with undifferentiated spondyloarthropathy with barely evident psoriasis [11]. Functional MRI of Psoriatic Arthritis of the Small Joints Functional imaging is aimed at determining the degree of inflammation. Special se-

quences such as dynamic contrast-enhanced MRI and unenhanced perfusion assessment with arterial spin labeling are used (Figs. 13 and 14). Contrast-enhanced MRI generally is needed for accurate assessment of activity in inflammatory arthritis, including psoriatic arthritis. Dynamic contrast-enhanced studies, however, facilitate precise differentiation between active inflammation (hyperemia) and chronic inactive (e.g., fibrotic) synovial thickening with late enhancement, mainly owing to slow contrast diffusion. Recent evidence [12] suggests that differences in late enhancement after contrast injection play an important role in differentiating from rheumatoid arthritis. Psoriatic arthritis exhibits a more abrupt drop (washout) in contrast-induced synovial signal intensity 15 minutes after contrast injection. MRI of Psoriatic Arthritis in Children The diagnosis of juvenile psoriatic arthritis is based on the criteria established by the International League of Associations for Rheumatology [13]. Disease onset after the age of 6 years differentiates psoriatic arthritis from oligoarthritis and polyarthritis [14]. The MRI findings in children differ considerably from those in adults, being much more subtle. Swelling of a single small joint; dactylitis, especially of a toe; multifocal bone marrow edema; and enhancement at both articular and nonarticular sites are highly suggestive of psoriatic arthritis. Distal interphalangeal joint involvement is found in 29% of patients, and dactylitis is found in 49%. Children have a much lower incidence of bone erosion than do adults, approximately 60% of whom have MRI findings of bone erosion [15]. Approximately 9% of patients with juvenile idiopathic arthritis have psoriatic arthritis [14]. Children with juvenile psoriatic arthritis are more likely to have small-joint disease than are those with pauciarticular juvenile idiopathic arthritis (Fig. 15). Thus the presence of small-joint and wrist disease or dactylitis alone may increase the ability to differentiate juvenile psoriatic arthritis from oligoarticular juvenile idiopathic arthritis. Conclusion The combination of findings such as enthesitis, multifocal bone marrow edema, periostitis, and extracapsular enhancement accompanying articular or tendon sheath synovitis is almost diagnostic of psoriatic arthritis. Juvenile psoriatic arthritis has marked differences from adult psoriatic arthritis, including subtler MRI changes and a greater proportion of cases with a subclinical (silent) course.

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References 1. Ibrahim G, Waxman R, Helliwell PS. The prevalence of psoriatic arthritis in people with psoriasis. Arthritis Rheum 2009; 61:1373–1378 2. Offidani A, Cellini A, Valeri G, Giovagnoni A. Subclinical joint involvement in psoriasis: magnetic resonance imaging and x-ray findings. Acta Derm Venereol 1998; 78:463–465 3. McGonagle D. Imaging the joint and enthesis: insights into pathogenesis of psoriatic arthritis. Ann Rheum Dis 2005; 64[suppl 2]:ii58–ii60 4. Boyle DL, Kavanaugh A. The pathobiology of psoriatic synovium. Curr Opin Rheumatol 2008; 20:404–407 5. Resnick D. Diagnosis of bone and joint disorders, 2nd ed. Philadelphia, PA: Saunders, 2002 6. Healy PJ, Groves C, Chandramohan M, Helliwell PS. MRI changes in psoriatic dactylitis: extent of pathol-

ogy, relationship to tenderness and correlation with clinical indices. Rheumatology 2008; 47:92–95 7. McQueen F, Lassere M, Østergaard M. Magnetic resonance imaging in psoriatic arthritis: a review of the literature. Arthritis Res Ther 2006; 8:207 8. Cimmino MA, Parodi M, Zampogna G, et al. Magnetic resonance imaging of the hand in psoriatic arthritis. J Rheumatol Suppl 2009; 83:39–41 9. Spira D, Henes J, Kötter I, Vogel M, Horger M. Psoriatic arthritis: conventional X-ray diagnosis in the hand and foot. Rofo 2009; 181:517–520 10. Marzo-Ortega H, McGonagle D, Rhodes LA, et al. Efficacy of infliximab on MRI-determined bone oedema in psoriatic arthritis. Ann Rheum Dis 2007; 66:778–781 11. Soscia E, Scarpa R, Cimmino MA, et al. Magnetic resonance imaging of nail unit in psoriatic arthritis. J Rheumatol Suppl 2009; 83:42–45

12. Schwenzer NF, Kötter I, Henes JC, et al. The role of dynamic contrast-enhanced MRI in the differential diagnosis of psoriatic and rheumatoid arthritis. AJR 2010; 194:715–720 13. Petty RE, Southwood TR, Manners P, et al; International League of Associations for Rheumatology. International League of Associations for Rheumatology classification of juvenile idiopathic arthritis: second revision, Edmonton, 2001. J Rheumatol 2004; 31:390–392 14. Flatø B, Lien G, Smerdel-Ramoya A, Vinje O. Juvenile psoriatic arthritis: longterm outcome and differentiation from other subtypes of juvenile idiopathic arthritis. J Rheumatol 2009; 36:642–650 15. Tehranzadeh J, Ashikyan O, Anavim A, Shin J. Detailed analysis of contrast-enhanced MRI of hands and wrists in patients with psoriatic arthritis. Skeletal Radiol 2008; 37:433–442

Fig. 1—63-year-old man with known psoriasis referred for evaluation of joint swelling. Axial fat-saturated gadolinium-enhanced T1-weighted MR image shows thickening of synovia of third metacarpophalangeal joint with marked enhancement (arrow) representing early monoarticular psoriatic arthritis. Erosion at ulnar aspect of head of third metacarpal also is evident.

Fig. 2—49-year-old woman with sausage digits of right index and long fingers without clinically evident psoriasis. A and B, Initial coronal (A) and axial (B) gadolinium-enhanced T1-weighted fat-saturated MR images of right hand show marked synovial and extrasynovial enhancement of flexor tendon sheaths of second and third digits (large arrows) and enhancement of corresponding tendons (small arrow). (Fig. 2 continues on next page)

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Fig. 2 (continued)—49-year-old woman with sausage digits of right index and long fingers without clinically evident psoriasis. C and D, Follow-up gadolinium-enhanced T1-weighted fat-saturated axial MR images 3 (C) and 5 months after start of treatment with tumor necrosis factor α blocker (adalimumab) (D) show temporal reduction of enhancement of synovial and extrasynovial membranes (large arrows) and corresponding tendons (small arrow) consistent with regression of inflammation related to interval treatment. Marked improvement is evident in D.

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D Fig. 3—50-year-old woman with dactylitis and known psoriasis. Axial fatsaturated gadolinium-enhanced T1-weighted image at level of proximal interphalangeal joints shows dactylitis affecting second through fifth digits and pronounced extracapsular hyperemia (right-facing arrows) with marked thickening of all digits. Ring finger (left-facing arrow) exhibits latticelike enhancement consistent with extraarticular inflammation. Pitting edema was diagnosed clinically.

Fig. 4—59-year-old woman with soft-tissue swelling of volar region of hand, carpal tunnel syndrome, and known psoriasis. A and B, Coronal fat-saturated T2-weighted (A) and axial fat-saturated gadolinium-enhanced T1-weighted (B) images show swelling and hyperemia of flexor tendon sheaths (all arrows), septation of vagina tendinum of flexor tendons (long arrow, A) consistent with fibrin threads as chronic inflammatory correlate, and marked thickening of synovial membrane of tendon sheath on volar side (short arrow, B). Additional synovial enhancement and thickening are evident around joints of fourth and fifth digits and in flexor tendon sheath of thumb.

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Fig. 5—51-year-old man with psoriasis referred for pain and impaired mobility of left thumb. Coronal fat-saturated T2-weighted image shows high signal intensity and moderate thickening of flexor pollicis longus tendon sheath (arrow). Synovial enhancement is evident in metacarpophalangeal joints of first and fifth digits, in carpometacarpal joint of thumb, and in triquetropisiform joint.

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Fig. 6—46-year-old man with rheumatoid arthritis. Axial fat-saturated gadoliniumMRI of Psoriatic enhanced T1-weighted image shows both synovial thickening with marked enhancement and extracapsular hyperemia (arrow). Mild synovial enhancement is evident in flexor tendon sheath of second digit, as are cystic changes in heads of first and fifth metacarpals.

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Fig. 7—69-year-old woman with psoriatic arthritis. A, Coronal oblique fat-saturated gadoliniumenhanced T1-weighted MR image shows periosteal thickening and hyperemia (arrow) in metacarpal bone of right first digit. B, Coronal oblique fat-saturated gadoliniumenhanced T1-weighted image shows progression at short-term follow-up with marked bone marrow hyperemia and soft-tissue enhancement (arrow). Periostitis in metaphyses and diaphyses is probably related to tenosynovitis and can lead to cloaking of entire phalanx over time.

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Fig. 8—52-year-old man with psoriatic arthritis. A, Coronal fat-saturated gadolinium-enhanced T1-weighted MR image shows bone marrow edema and hyperemia beginning at corner of proximal phalanx of thumb at insertion of thenar musculature and then spreading to involve adjacent bone (arrow). B, Axial fat-saturated gadolinium-enhanced T1-weighted MR image shows marked enhancement related to hyperemia at synovioenthetic complex (arrow). Extracapsular hyperemia (arrow) also is evident. C, Axial fat-saturated gadolinium-enhanced T1-weighted MR image at short-term follow-up shows progression of periarticular inflammation (arrows) and bone marrow hyperemia.

Fig. 9—44-year-old woman with psoriatic arthritis. Axial fat-saturated gadoliniumenhanced T1-weighted MR image shows enhancement (arrow) of muscular fascia of dorsal aspect of hand related to extracapsular inflammation. Sign is not typical of psoriatic arthritis.

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Fig. 10—63-year-old man with recently diagnosed psoriatic arthritis. A, Coronal T1-weighted MR image of left hand shows erosions at both ulnar and radial aspects of fifth metacarpal head in so-called bare areas (arrows). B, Coronal T1-weighted image of right hand shows erosion is in central area of joint surface of fourth metacarpal bone (long arrow). Bony proliferation (short arrows) is evident at third metacarpal head on both radial and ulnar sides. C, Axial gadolinium-enhanced T1-weighted fat-saturated MR image at carpal level shows enhancement of both extensor and flexor tendon sheaths consistent with tenosynovitis and focal erosion (arrow) in hamate bone. Tenosynovitis around carpal bones is evident.

Fig. 11—45-year-old woman with late psoriatic arthritis. A and B, Coronal (A) and sagittal (B) T1-weighted images show telescoping (arrow, A) and volar subluxation (arrow, B) of metacarpophalangeal joint of third digit corresponding to late psoriatic arthritis.

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Fig. 12—50-year-old woman with late psoriatic arthritis. A, Coronal fat-saturated T2-weighted MR image of right hand shows advanced bone destruction adjacent to joints and marked osseous proliferations with subluxation. Bony proliferations are present where tendons and ligaments (joint capsule) insert into bones (long arrows) and eburnation of phalanges (small arrows). Lack of apposition of adjacent bony margins (in proximal interphalangeal joints of third, fourth, and fifth digits) differentiates psoriatic arthritis from osteoarthritis, which is characterized by closely applied, undulating osseous surfaces. B, Coronal T1-weighted MR image shows areas of low signal intensity (short arrows) in proximal interphalangeal joints of fourth and fifth digits of left hand mainly caused by eburnation and to lesser extent by edema. Marked swelling of joint capsule and adjacent bone proliferation (long arrows) are evident. In fifth digit subcutaneous fat signal suppression (asterisk) is consistent with extrasynovial inflammation. Widening of joint spaces and expansion of middle phalangeal bases are due to destruction of proximal interphalangeal joints. Former is uncommon in rheumatoid arthritis.

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Fig. 13—53-year-old man with late psoriatic arthritis. A, Axial arterial spin-labeled (true fast imaging with steady-state precession sequence) color-coded synovial perfusion quantification image at level of metacarpophalangeal joints yields perfusion value of 198 ± 63 (SD) mL/100g/min and shows isolated monoarthritis (arrow) of first digit. B, Dynamic contrast-enhanced MR image at same level as A shows concordant contrast enhancement (arrow) due to hyperemia and inflammation.

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Fig. 14—45-year-old woman with late psoriatic arthritis. Dynamic contrastenhanced MRI readout acquired after contrast administration shows decrease (washout) in contrast-induced synovial signal intensity 15 minutes after contrast injection. Compared with rheumatoid arthritis, psoriatic arthritis exhibits earlier peak enhancement on dynamic contrast-enhanced MR images and characteristic washout phenomenon due to increased vascularization and reduced permeability of vascular endothelium that correlates with histologic data. Unlike that of psoriatic arthritis, signal intensity of rheumatoid arthritis synovial usually has persistent plateau due to increased diffusion in pannus 15 minutes after IV contrast administration. AU = arbitrary units.

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Fig. 15—4-year-old girl with newly diagnosed juvenile psoriatic arthritis. A and B, Axial (A) and coronal (B) fat-saturated gadolinium-enhanced T1-weighted MR images show marked extraarticular swelling and contrast enhancement of wrist that includes both flexor (long arrow, A) and extensor (short arrow, A) tendon sheaths. Diffuse extraarticular enhancement (arrow, B) is evident on radial side of wrist with pandactylitis.

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