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Updated: Mar 26, 2026
Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
Published on: December 18, 2016
Muscle Involvement in Polyarteritis Nodosa: Report of Eight Cases With Characteristic Contrast Enhancement Pattern on
Yusuhn Kang1, Sung Hwan Hong1, Hye Jin Yoo1
11 Department of Radiology, Seoul National University College of Medicine, 101 Daehak-ro Jongno-gu, Seoul 110-744, Korea.
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.
Materials And 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.
Conclusion:
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.
Insights
Polyarteritis nodosa (PAN) can manifest as patchy or diffuse muscle signal changes on MRI. Characteristic findings include fluffy, vessel-centered enhancement, suggesting PAN in differential diagnoses.
Area of Science:
- Radiology
- Musculoskeletal Imaging
- Rheumatology
Background:
- Polyarteritis nodosa (PAN) is a systemic vasculitis.
- Muscle involvement is a recognized but less commonly described manifestation of PAN.
Purpose of the Study:
- To characterize magnetic resonance imaging (MRI) findings in patients with muscle involvement due to PAN.
- To emphasize the contrast enhancement patterns indicative of PAN.
Main Methods:
- Retrospective review of MRI studies from eight patients diagnosed with PAN.
- Evaluation of affected structures, signal intensities on T1- and T2-weighted images, and contrast enhancement patterns.
Main Results:
- Muscle lesions were predominant in seven patients; fascial involvement was noted in one.
- MRI revealed diffuse or patchy muscle hyperintensity on T2-weighted images.
- Contrast-enhanced MRI showed characteristic "cotton-wool" enhancing lesions centered on vessels in six patients, with associated fascial or periosteal enhancement in some.
Conclusions:
- MRI findings of patchy or diffuse muscle signal changes should raise suspicion for PAN.
- The presence of fluffy, vessel-centered enhancement on contrast-enhanced MRI is a key indicator of muscle involvement in PAN.
- Associated fascial and periosteal enhancement may also be observed in PAN.
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