Can a normal MRI (Magnetic Resonance Imaging) of the brain and orbits with and without contrast rule out cancer in a child with progressive facial asymmetry?

MRI Brain and Orbits with and without Contrast for Progressive Facial Asymmetry in Children

A normal MRI of the brain and orbits with and without contrast cannot definitively rule out all cancers in a child with progressive facial asymmetry, but it is the most sensitive imaging modality available and will detect the vast majority of clinically significant malignancies in this anatomic region. 1

Why MRI with Contrast is the Optimal Study

MRI of the head and orbits with and without IV contrast is the most useful imaging modality for evaluating suspected orbital or intracranial masses in children, providing superior soft tissue characterization compared to CT and avoiding radiation exposure. 1

• The addition of contrast is critical because postcontrast enhancement helps differentiate malignant masses (like retinoblastoma) from benign conditions and provides better delineation of tumor extent, including retrolaminar optic nerve infiltration, orbital invasion, and intracranial spread. 1

• MRI can detect optic pathway gliomas (which comprise 3-5% of pediatric brain tumors), meningiomas, and other intracranial tumors that may present with facial asymmetry. 1, 2, 3

What a Normal MRI Can and Cannot Rule Out

What It Effectively Rules Out:

• Intraorbital and intraocular malignancies including retinoblastoma, which MRI with contrast can identify with high sensitivity through characteristic enhancement patterns. 1

• Intracranial tumors affecting the brain, skull base, or cavernous sinus that could cause facial asymmetry through mass effect or nerve involvement. 1

• Optic pathway gliomas and other anterior visual pathway tumors that might present with subtle facial changes. 1, 2

Important Limitations:

• Small cortical bone lesions may be better visualized on CT, as MRI has decreased spatial resolution for osseous detail compared to CT. 1

• Very small or early-stage tumors below the resolution threshold of MRI (typically <3-5mm) could theoretically be missed, though this is uncommon for lesions causing progressive clinical symptoms. 1

• Soft tissue sarcomas in the facial soft tissues outside the orbit may require dedicated facial MRI sequences for optimal detection. 1

Clinical Context Matters

Progressive facial asymmetry in children has multiple etiologies, and the clinical presentation guides the interpretation of imaging:

• Hemifacial microsomia is a common craniofacial anomaly that demonstrates progressive asymmetry with growth but is not malignant and typically diagnosed clinically. 4

• Benign developmental asymmetry is common in healthy children and may fluctuate during growth, with studies showing statistically significant mandibular asymmetry in normal subjects. 5, 6

• Facial nerve palsy from intracranial masses (like meningiomas) can present initially as facial asymmetry, making MRI essential to distinguish from benign causes. 3

Critical Pitfalls to Avoid

• Do not assume facial asymmetry is benign without imaging if it is progressive, unilateral, or associated with other neurological signs, as case reports document children with sphenoid wing meningiomas presenting initially with only facial asymmetry. 3

• Do not use CT as the initial imaging modality for suspected orbital or intracranial pathology in children, as it provides inferior soft tissue detail and exposes the child to unnecessary radiation. 1, 2

• Do not omit contrast when malignancy is a consideration, as the enhancement pattern is critical for differentiating benign from malignant lesions and assessing tumor extent. 1

Algorithmic Approach

For a child with progressive facial asymmetry:

1. Perform thorough clinical examination looking specifically for: upper versus lower motor neuron facial nerve involvement, proptosis or enophthalmos, visual changes, cranial nerve deficits, and signs of raised intracranial pressure. 1, 3

2. Order MRI brain and orbits with and without IV contrast as the initial imaging study if any concerning features are present (progressive asymmetry, neurological signs, visual symptoms, or inability to explain asymmetry by developmental causes). 1, 2

3. If MRI is completely normal and clinical examination shows no neurological deficits, the likelihood of a clinically significant malignancy is very low, though not zero. 1, 2

4. Consider additional imaging (such as dedicated facial MRI or CT for bone detail) only if clinical suspicion remains high despite normal brain and orbital MRI, or if symptoms progress. 1

Quality of Life Considerations

The decision to pursue imaging must balance the risk of missing a treatable malignancy against the burden of unnecessary testing. MRI with contrast in children often requires sedation, which carries its own risks. 1 However, missing an intracranial tumor like meningioma or optic pathway glioma can result in permanent neurological deficits, blindness, or death, making the threshold for imaging appropriately low when asymmetry is progressive or unexplained. 2, 3