title: Muscle Involvement in Polyarteritis Nodosa: Report of Eight Cases With Characteristic Contrast Enhancement Pattern on MRI.
abstract: OBJECTIVE
  The purpose of this study is to describe MRI findings of muscle involvement in patients with polyarteritis nodosa (PAN), with an emphasis on the contrast enhancement characteristics.
  
  
  METHODS
  MRI studies of eight patients with PAN were retrospectively reviewed (four male and four female patients; mean age at presentation, 34.3 years; age range, 7-64 years). MR images were evaluated focusing on the following features: affected structures (muscle, fascia, or periosteum), lesion signal intensity and characteristics on T1-and T2-weighted images, and contrast enhancement patterns.
  
  
  RESULTS
  Seven patients had lower leg involvement, and one had thigh involvement. In the seven patients with lower leg involvement, the main lesions were within the muscles, whereas in one patient with thigh involvement, the investing fascia was mainly involved. In the seven patients with predominantly muscle involvement, T2-weighted images showed either diffuse (n = 3) or patchy (n = 4) hyperintensity of the affected muscles. On contrast-enhanced images, small fluffy enhancing lesions centered on vessels (i.e., the "cotton-wool appearance") were noted within the affected muscles in six patients. In the one patient with mainly fascial lesions, the investing fascia showed diffuse enhancement. Periosteal enhancement was found along the tibial cortex in 50% (4/8) of our patients.
  
  
  CONCLUSIONS
  PAN should be considered a differential diagnosis in cases where MR images show patchy or diffuse muscle signal changes. Muscle involvement in PAN may show fluffy enhancing lesions centered on vessels on contrast-enhanced images and may accompany fascial or periosteal enhancement.
authors.affiliation: 1 Department of Radiology, Seoul National University College of Medicine, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea.
authors.forename: Yusuhn
authors.initials: Y
authors.lastname: Kang
authors.affiliation: 1 Department of Radiology, Seoul National University College of Medicine, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea.
authors.forename: Sung Hwan
authors.initials: SH
authors.lastname: Hong
authors.affiliation: 1 Department of Radiology, Seoul National University College of Medicine, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea.
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Yoo
authors.affiliation: 1 Department of Radiology, Seoul National University College of Medicine, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea.
authors.forename: Ja-Young
authors.initials: JY
authors.lastname: Choi
authors.affiliation: 2 Division of Rheumatology, Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jin Kyun
authors.initials: JK
authors.lastname: Park
authors.affiliation: 1 Department of Radiology, Seoul National University College of Medicine, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea.
authors.forename: Jina
authors.initials: J
authors.lastname: Park
authors.affiliation: 1 Department of Radiology, Seoul National University College of Medicine, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea.
authors.forename: Heung Sik
authors.initials: HS
authors.lastname: Kang
mesh_terms: D000293:Adolescent; D000328:Adult; D003287:Contrast Media; D005260:Female; D005682:Gadolinium; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*; D010488:Polyarteritis Nodosa / Q000473:pathology*; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D005682:Gadolinium
keywords: MRI; fascia; muscles; polyarteritis nodosa; vasculitis