Should a contrast or non-contrast MRI (Magnetic Resonance Imaging) be used for the workup of myositis?

MRI for Myositis Workup: Contrast vs Non-Contrast

Non-contrast MRI using T2-weighted/STIR sequences is the preferred initial imaging approach for suspected myositis, as these sequences are highly sensitive for detecting muscle inflammation and edema without requiring gadolinium administration. 1

Primary Recommendation

The European League Against Rheumatism specifically recommends T2-weighted/STIR sequences as the preferred protocol for detecting muscle inflammation in dermatomyositis and other inflammatory myopathies. 1 These non-contrast sequences enhance visualization of edema and inflammatory changes that are the hallmark of active myositis. 1

When Non-Contrast MRI is Sufficient

• Initial diagnostic workup: Non-contrast MRI should be included as part of the comprehensive assessment when myositis is suspected, even when clinical signs are absent. 1

• Disease activity monitoring: Non-contrast MRI is highly effective for monitoring disease progression over time and assessing treatment response. 1

• Pattern recognition: Non-contrast sequences (T1-weighted and T2-weighted fat suppressed/STIR) provide excellent characterization of muscle edema and fat replacement, which are sufficient for diagnosis in most cases. 2

• Highest sensitivity: T2-weighted MRI with fat suppression or STIR sequences represent the most sensitive and specific routine method for polymyositis and dermatomyositis imaging. 3

Role of Contrast-Enhanced MRI

While non-contrast imaging is generally sufficient, contrast may provide additional information in specific circumstances:

• Abscess identification: Contrast-enhanced MRI aids in identifying abscesses and areas of necrosis when infection is a consideration. 4

• Vascular assessment: Contrast can help delineate vascular involvement and assess muscle perfusion patterns. 4

• Atypical presentations: When the clinical presentation is unclear or overlaps with other conditions, contrast may provide supplementary diagnostic information. 1

However, the ACR Appropriateness Criteria for soft tissue infections note that both contrast-enhanced and non-contrast MRI are considered equivalent alternatives for musculoskeletal inflammatory conditions. 4

Practical Implementation Algorithm

1. Start with non-contrast MRI using T2-weighted/STIR sequences for all suspected myositis cases. 1

2. Ensure expert interpretation by a radiologist experienced in muscle imaging. 1

3. Reserve contrast administration for cases where:

   • Abscess or necrosis is suspected
   • Vascular complications need evaluation
   • Initial non-contrast findings are equivocal

4. Use MRI to guide muscle biopsy site selection when tissue diagnosis is needed, particularly in atypical presentations. 1, 3

Common Pitfalls to Avoid

• Don't routinely order contrast when the clinical question is straightforward inflammatory myopathy—non-contrast sequences provide the necessary diagnostic information. 1, 2

• Don't skip MRI interpretation by an expert—accurate assessment of inflammatory changes requires specialized radiologic expertise. 1

• Don't use MRI as the sole diagnostic tool—integrate imaging findings with clinical examination, laboratory values (CK, aldolase, inflammatory markers), EMG, and potentially muscle biopsy for definitive diagnosis. 4

• Don't forget cardiac evaluation—when myositis is confirmed, baseline ECG and echocardiography are necessary to assess for myocardial involvement. 5

Alternative When MRI Unavailable

When MRI is not accessible, increased muscle echo intensity on ultrasonography performed by an experienced sonographer may serve as an alternative method to detect myositis, though it is less sensitive than MRI. 1 Ultrasound is particularly useful for detecting fat replacement and fibrosis in chronic disease. 2