Clinical Musculoskeletal Imaging

Utility of MRI Findings in Inflammatory

Christopher J. Hanrahan; Barry G. Hansford

Department of Radiology and Imaging Sciences, University of Utah School of Medicine, Salt Lake City, UT, USA

Introduction Case 1 mass-like appearance and lack of zonal peripheral mineralization. In MR imaging can provide important A 37-year-old male rancher devel- this particular case, there is no initial information for establishing a diag- oped , , and slight muscle abnormality visible on the nosis in inflammatory myopathies, stiffness in his left one month T1 sequence (Fig. 1A), but rim of low and routine MRI sequences can previously and noticed a mass. He signal intensity on the fluid sensitive help exclude alternative diagnoses. denied any or constitutional sequence indicates an underlying mass With MRI, muscle pathologic findings symptoms. On his initial examina- (Fig. 1C), which in some cases is only typically fall into three categories: tion, he was afebrile with mild appreciated after subsequent imaging mass lesions, fatty atrophy, and swelling of his left thigh with [2]. A mass usually develops within edema [1]. Masses can include tenderness and a palpable mass. 6-8 weeks and extensive edema has muscle injury with hematoma or There was no redness or warmth to been described in lesions that are ossificans, sarcoma or touch. He showed 4/5 strength with imaged within 8 weeks of the inciting pseudosarcoma, abscess, parasitic extension, but there was no atrophy event [2]. Clinical and imaging infection, or sarcoidosis. Fatty infil- of the left thigh. His initial radio- follow-up can confirm the diagnosis tration and atrophy is the end-stage graphs were negative. His initial (Figure 1D-F). The ossific rim usually result of many muscle pathologies, MRI showed extensive edema within appears after 4-6 weeks, but early in including disuse, , tendon the vastus medialis and intermedius its formation may only be visible by injury, or denervation. Muscle edema muscles with a central mass with CT [2]. Post-contrast imaging will is the third muscle pathology com- low intensity rim (Fig. 1A-C). Follow- demonstrate enhancement due to monly encountered with clinical up MRI three months later, showed its extensive vascularity [2]. Biopsy MR imaging. Muscular edema can decreased muscular edema and should be avoided, especially early be caused by muscle injury, denerva- development of a discreet mass with (within 1-2 weeks) when the mass tion, drug-induced myopathy, or low signal intensity rim (Fig. 1D-F). could potentially be confused upon inflammatory myopathies including Diagnosis: Myositis Ossificans histology with extraskeletal osteosar- paraneoplastic syndromes. The focus Myositis ossificans is a benign, coma resulting in aggressive therapies of this article is to present several self-limited condition that presents for an inherently benign condition [3]. cases of muscle edema to demon- following an injury to muscle [2]. strate the utility of MR imaging in The presenting clinical scenario may simplifying the differential diagnosis Case 2 mimic muscle denervation or myopa- based on the distribution of findings thy and since patients frequently A 56-year-old female with renal cell and clinical history. do not recall an inciting event. carcinoma developed right lower The initial imaging may also be extremity weakness, primarily with confusing, especially on MRI, given extension following radical right the intramuscular inflammatory nephrectomy, retroperitoneal lymph

Key Points

Inflammatory myopathies encompass several rare diseases that affect the lower extremities greater than the upper extremities and include , polymyositis, and dermatomyositis. The presence of inflammatory myopathy must be distinguished from other potential causes of muscle pathology, including muscle injury, nerve injury, , tumor and diabetic ischemic myopathy. MR imaging can help to exclude other pathologies and can provide important information about the location and extent of . For cases in which a specific diagnosis by MRI alone may not always be possible, MRI may provide value in localizing the greatest areas of inflammation to focus muscle biopsy, since treatments may differ depending on the underlying etiology.

26 MAGNETOM Flash | (66) 3/2016 | www.siemens.com/magnetom-world Musculoskeletal Imaging Clinical node dissection, and inferior vena Case 3 knee extensors (Fig. 3). Initial muscle cava thrombectomy, which was com- biopsy of her left vastus lateralis was A 58-year-old female who presented plicated by iliopsoas and paraspinal negative, while subsequent biopsy with a 12-day rash that initially hematoma. Five months following of her right semitendinosus muscle started on her chest and back and surgery she was evaluated and found revealed perivascular inflammation. spread to her neck, face and fore- to have 0 out of 5 right quadriceps head. She revealed progressive Diagnosis: Dematomyositis muscle strength compared to 5 out over the course Dermatomyositis is an autoimmune of 5 strength within the extensor of the past year primarily within inflammatory myopathy that results hallucis longus, tibialis anterior, her shoulders and hips manifest by in subacute symmetric proximal mus- gastrocnemius, and soleus muscles. increasing difficulty brushing her cle weakness. There is a predilection Pelvic MR imaging was performed and teeth and climbing stairs. She had for women and age can vary, but has demonstrates unilateral muscle edema been treated with a steroid taper a peak between 30 and 50 years of within the quadriceps musculature, without significant improvement of age [5]. The differential diagnosis specifically the rectus femoris and her rash or her muscle weakness. On of muscle weakness includes other vastus lateralis muscles (Fig. 2). examination, she was afebrile with inflammatory myopathies, such as Diagnosis: Femoral Nerve Injury an erythematous rash over her upper, polymyositis and inclusion body MR imaging can help distinguish a back, chest, and neck with macules myositis. In this particular patient the nerve injury edema pattern from and papules over her lateral presence of a rash favors dermatomy- myopathy. Most commonly, MR imag- and elbows, but no rash over her ositis over polymyositis and inclusion ing of denervation is unilateral and eyelids. She was unable to lift her body myositis, however it is impor- demonstrates edema and possibly arms off the bed and had 3 out of 5 tant to exclude inclusion body myosi- atrophy of the musculature within muscle strength with knee extension tis, as this disease does not respond a specific and typical distribution of and mild decreased grip strength. to most therapies, including steroids the affected nerve. Although electro- She had an elevated creatine kinase [6, 7], as reportedly occurred in the myography (EMG), nerve conduction at 678 (units/liter; reference range short term with this patient. The dis- studies, or ultrasound can be used to 20-180 U/l) with a normal erythro- ease is characterized by an erythema- localize nerve injury, MR imaging has cyte sedimentation rate and C-reac- tous rash and often has Gottron’s the advantage of greater sensitivity, tive protein. Tests for anti-nuclear papules over extensor surfaces as in non-invasiveness compared to EMG, antibody, lyme disease, and coccidio- this patient over the elbows. They superior anatomic resolution, and mycosis were negative. An MRI of frequently also have a heliotrope rash in some cases allows identification her thighs demonstrated relatively characterized by erythematous eye- of aberrant nerve supply [4]. symmetric muscle edema within her lids, which this patient did not have.

1A 1B 1C 1D

1E 1F 1 Myositis ossificans. Early in the course of the disease (1A-C) the muscle appears normal on T1w (1A) and shows extensive edema within the affected muscles (vastus medialis and intermedius) on fluid sensitive sequences (1B, T2w fs). On the coronal T2w fs image (1C), a low signal intensity rim is appreciated. Follow-up imaging in three months (1D-F), demonstrates significantly decreased edema, with increased conspicuity of the soft tissue ‘mass’ with increased T1 signal (1D) likely corresponding to fatty infiltration between trabeculae [2] and thickened low intensity rim (1E), which reflects the zonal phenomenon of peripheral mineralization which is now clearly demon- strated via radiography (1F).

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2A 3A

3B

2B

3C

2 Right femoral distribution denervation. Five months 3 Dermatomyositis. Axial proton density with fat suppression following right nephrectomy for renal cell carcinoma, (3A) and coronal STIR (3B) images demonstrate bilateral the patient has edema within the rectus femoris and muscle edema in the rectus femoris and tensor fascia vastus lateralis muscles (arrow in 2A; T2w fat suppressed lata muscles (arrow on right side and arrowhead left side). axial image) as well as mild atrophy (arrow in 2B; T1w Distal axial proton density-weighted image with fat coronal image). suppression demonstrates asymmetric involvement of the right greater than left semitendinosus muscle (arrow) and no involvement of the left vastus lateralis muscle (arrowhead), which is consistent with the negative biopsy result performed at this location.

4A 4B 4 Polymyositis with lympho- ma. Coronal STIR image (4A) of the pelvis demon- strates symmetric edema in multiple muscle groups (arrowheads). Maximum intensity projection (MIP) image from subsequent PET/CT scan (4B) demon- strates FDG uptake in extensive retroperitoneal lymphadenopathy (arrow) and splenic uptake (arrow- head) from lymphomatous infiltration.

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MR imaging Case 4 References A 59-year-old male presented with 1 May, D.A., et al., Abnormal signal MRI can be helpful in confirming a one-month history of proximal intensity in at MR imaging: patterns, pearls, and pitfalls. the presence of myopathy, excluding muscle weakness, arthralgia, fevers, non-inflammatory causes of muscle Radiographics, 2000. 20 Spec No: weight loss, and truncal rash, along p. S295-315. disease and, in some cases, differ- with progressive shortness of breath. 2 Kransdorf, M.J., J.M. Meis, and entiation between inflammatory He underwent a laboratory workup J.S. Jelinek, Myositis ossificans: MR myopathies. Ultimately, the definitive and was found to be anemic with appearance with radiologic-pathologic diagnosis is made through muscle elevated c-reactive protein and ESR correlation. American Journal of Roent- biopsy. The distinguishing features and a positive ANA. His SPEP was genology, 1991. 157(6): p. 1243-1248. 3 Hoch, B. and A. Montag, Reactive bone of the inflammatory myopathies negative. He was initially put on by histology include perivascular lesions mimicking neoplasms. Semin steroids with a presumed lupus diag- Diagn Pathol, 2011. 28(1): p. 102-12. inflammation with dermatomyositis, nosis, which helped his weakness. 4 Kim, S.-J., et al., MR Imaging Mapping endomysial inflammation with A subsequent elevated LDH and of Skeletal Muscle Denervation in polymyositis, and both the presence lymphadenopathy by computed Entrapment and Compressive Neuropa- of inclusion bodies and endomysial tomography as well as a negative thies. RadioGraphics, 2011. 31(2): inflammation in inclusion body bone marrow biopsy prompted a p. 319-332. 5 Mammen, A.L., Dermatomyositis and myositis [5, 7-10]. Theoretically, referral to an oncologist. He then this would translate into differences polymyositis: Clinical presentation, underwent a lymph node biopsy autoantibodies, and pathogenesis. Ann in MR imaging, but in practice the and MRI of the pelvis for muscle N Y Acad Sci, 2010. 1184: p. 134-53. edema and enhancement patterns in weakness (Fig. 4). 6 Greenberg, S.A., Inclusion body myositis. individual muscles overlap, especially Curr Opin Rheumatol, 2011. 23(6): between dermatomyositis and polymy- Diagnosis: Polymyositis with p. 574-8. ositis. Dermatomyositis, with its lymphoma 7 Greenberg, S.A., Pathogenesis and perivascular inflammation, tends to MR imaging revealed a highly therapy of inclusion body myositis. have more perifascial muscle edema symmetrical myopathy without Curr Opin Neurol, 2012. 25(5): p. 630-9. 8 Needham, M. and F.L. Mastaglia, than polymyositis, which occurs more significant perifascial edema, which was confirmed polymyositis by Sporadic inclusion body myositis: A frequently in the juvenile form of review of recent clinical advances and biopsy. Whenever the diagnosis of the disease, but nevertheless is not current approaches to diagnosis and diagnostic [11-13]. However, one polymyositis or dermatomyositis is treatment. Clin Neurophysiol, 2015. distinguishing feature of inclusion made, an occult malignancy should 9 Iaccarino, L., et al., The clinical features, body myositis by MR imaging is the be considered [10, 16]. Malignancy diagnosis and classification of dermato- relative sparing of the rectus femoris associated with these inflammatory myositis. J Autoimmun, 2014. 48-49: p. 122-7. muscle early in the disease process myopathies is defined as a malig- nancy diagnosed within 3 months 10 Milisenda, J.C., A. Selva-O’Callaghan, and the predominant involvement of and J.M. Grau, The diagnosis and classi- of the diagnosis of inflammatory flexor digitorum profundus in the fication of polymyositis. J Autoimmun, forearm [14, 15]. In this case, which myopathy and occurs in 3-6% of 2014. 48-49: p. 118-21. is relatively early in the disease process polymyostis and 13-29% of dermato- 11 Ladd, P.E., et al., Juvenile dermatomyo- based on the relative paucity of muscle myositis [10, 16]. Despite the sitis: correlation of MRI at presentation atrophy, there is involvement of the relatively high association with with clinical outcome. AJR Am J Roent- genol, 2011. 197(1): p. W153-8. rectus femoris muscle suggesting underlying malignancy and likely paraneoplastic etiology, there is 12 Tomasova Studynkova, J., et al., The role that this is not inclusion body myositis, of MRI in the assessment of polymyositis no current consensus regarding despite a history of lack of response to and dermatomyositis. Rheumatology steroids. a standard malignancy workup for (Oxford), 2007. 46(7): p. 1174-9. this patient population. 13 Hernandez, R.J., et al., MR imaging in children with dermatomyositis: musculo- skeletal findings and correlation with clinical and laboratory findings. AJR Am J Roentgenol, 1993. 161(2): p. 359-66. 14 Adams, E.M., et al., The idiopathic Contact inflammatory myopathies: spectrum of MR imaging findings. Radiographics, Christopher J. Hanrahan, M.D., Ph.D. 1995. 15(3): p. 563-74. Associate Professor and Section Chief, 15 Cox, F.M., et al., Magnetic resonance Musculoskeletal Imaging imaging of skeletal muscles in sporadic Department of Radiology and inclusion body myositis. Rheumatology, Imaging Sciences 2011. 50(6): p. 1153-1161. University of Utah School of Medicine 16 Andras, C., et al., Dermatomyositis and 30 North 1900 East polymyositis associated with malig- Salt Lake City, UT, 84132, USA nancy: a 21-year retrospective study. Barry G. Christopher [email protected] J Rheumatol, 2008. 35(3): p. 438-44. Hansford J. Hanrahan

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