Progressive Facial Asymmetry in a Four-Year-Old with Normal Noncontrast MRI
A normal noncontrast MRI does not exclude cancer in a four-year-old with progressive facial asymmetry, and contrast-enhanced MRI of the orbits, face, and neck is urgently needed to evaluate for malignancies that are invisible without contrast administration. 1, 2
Why Noncontrast MRI is Inadequate
The American College of Radiology explicitly states that noncontrast imaging alone cannot adequately delineate soft tissue tumors from surrounding structures, and combined pre- and postcontrast imaging provides the best opportunity to correctly identify and delineate tumors. 2 The absence of IV contrast limits the ability to accurately delineate tumor margins, soft tissue extent, perineural spread, and subtle marrow involvement. 2
Critical imaging protocol error: Standard brain MRI protocols do not adequately cover the face or orbits for detailed evaluation of facial asymmetry, and the coverage and sequences used in typical brain MRI may be insufficient to completely evaluate pathology causing facial asymmetry. 2
Malignancies That Can Cause Progressive Facial Asymmetry with Normal Noncontrast MRI
Primary Malignant Considerations
Plexiform neurofibroma is the most important diagnosis to consider, as it most commonly presents before age 5 with periorbital asymmetry or facial distortion. 2 These tumors show characteristic intense enhancement on contrast MRI that is invisible on noncontrast sequences. 1
Rhabdomyosarcoma is the most common soft tissue sarcoma in children and can present with progressive facial asymmetry. 2 Contrast enhancement is essential for delineating tumor extent and distinguishing tumor from inflammatory changes. 2
Salivary gland tumors warrant particular attention:
- Mucoepidermoid carcinoma, adenoid cystic carcinoma, and acinic cell carcinoma are the most common malignant salivary gland tumors in children. 3
- Adenoid cystic carcinoma is notorious for perineural spread, which in early stages may be asymptomatic but causes progressive facial asymmetry. 3
- These tumors require contrast-enhanced MRI for proper characterization, as noncontrast imaging cannot adequately demonstrate tumor extent or perineural involvement. 3
Lymphoma can present with progressive facial asymmetry and requires contrast for proper tissue characterization. 2
Vascular Malformations Mimicking Malignancy
Low-flow venous malformations are the most common cause of progressive facial asymmetry in children and show characteristic intense enhancement on contrast MRI that is completely invisible on noncontrast sequences. 1 Vascular malformations require contrast for proper characterization, as noncontrast MRI cannot adequately differentiate between low-flow and high-flow types. 1
Large segmental facial hemangiomas (>5 cm) can cause progressive asymmetry and warrant evaluation for PHACE syndrome. 1 Contrast administration is essential for detecting active hemangioma tissue and differentiating from involuting lesions. 1
Correct Imaging Protocol
Order MRI orbits, face, and neck without and with IV contrast urgently (within days, not weeks). 2 The American College of Radiology consistently recommends "MRI orbits, face, and neck" as a unified protocol for evaluating facial asymmetry, not "MRI orbits" or "MRI brain" alone. 2
Use thin-section sequences focused on the affected facial region with contrast enhancement showing sensitivity of 83% and specificity of 95% for differentiating pathology types. 1
Physical Examination Priorities
Examine for neurofibromatosis type 1 stigmata: café-au-lait spots (≥6 spots >5mm prepubertal), axillary or inguinal freckling, and Lisch nodules on slit-lamp examination. 2
Palpate the facial asymmetry for texture characteristics: soft versus firm, mobile versus fixed, or "bag of worms" texture suggestive of plexiform neurofibroma. 2
Do not biopsy any suspected plexiform neurofibroma before obtaining contrast-enhanced imaging and potential genetics consultation. 2
Additional Workup if High-Flow Vascular Malformation Identified
The American Academy of Pediatrics recommends obtaining echocardiography to assess for cardiac anomalies associated with PHACE syndrome if high-flow vascular malformation is identified. 1
Sedation Considerations
Most 4-year-olds require sedation or general anesthesia for contrast-enhanced MRI to ensure adequate image quality. 1 Coordinate with the anesthesia team to optimize the imaging protocol and minimize sedation time while obtaining necessary sequences. 1