Progressive Facial Asymmetry in a 4-Year-Old with Normal Non-Contrast Imaging
The most critical next step is obtaining brain MRI with contrast and MRI of the orbit, face, and neck with contrast, as the normal non-contrast studies performed are inadequate to exclude serious intracranial pathology, facial nerve disorders, or vascular abnormalities that can cause progressive facial asymmetry in children. 1, 2, 3
Why Current Imaging is Insufficient
Non-contrast MRI and CT miss critical pathologies: The ACR Appropriateness Criteria rates MRI head without and with IV contrast as 8/9 (usually appropriate) and MRI orbit/face/neck without and with IV contrast as 9/9 (usually appropriate) for facial nerve disorders causing weakness or paralysis of facial expression. 1
Progressive asymmetry only with smiling indicates incomplete facial nerve dysfunction: The American Academy of Otolaryngology-Head and Neck Surgery identifies that incomplete or mild facial nerve dysfunction becomes apparent only with voluntary facial movement, causing asymmetry specifically with smiling. 3
Non-contrast studies cannot adequately evaluate: Tumors affecting the facial nerve, meningeal infiltration, vascular malformations, or enhancing lesions along the facial nerve pathway—all of which require contrast administration for detection. 1
Most Likely Diagnostic Considerations
Primary Differential Diagnoses
Facial Nerve Pathology (CN VII):
- Incomplete facial nerve palsy or paresis: Manifests as asymmetry only during voluntary movement (smiling), with normal appearance at rest. 3
- Facial nerve tumor or schwannoma: Requires contrast-enhanced MRI for detection along the nerve pathway from brainstem to peripheral branches. 1
- Bell's palsy (atypical presentation): Though typically acute, can present with progressive weakness; requires contrast imaging to exclude other causes. 1
Asymmetric Crying Facies (ACF):
- Congenital hypoplasia/agenesis of depressor anguli oris muscle: Causes asymmetry specifically with smiling, crying, or speaking loudly, present since birth but may become more noticeable with growth. 4
- Critical association with congenital malformations: ACF is a marker for cardiac defects (patent foramen ovale, ventricular septal defects), renal agenesis, skeletal abnormalities, and 22q11.2 deletions. 4
- Progressive appearance: While congenital, asymmetry becomes more apparent as facial expressions develop and facial structures grow. 4
Hemifacial Microsomia:
- Progressive asymmetry with growth: Shows increasing asymmetry as the child develops, affecting skeletal and soft tissue structures. 2, 3, 5
- Category (f) asymmetry pattern: More pronounced facial asymmetry with cheek flattening and slanting of midface. 6
Intracranial Mass or Tumor:
- Urgent to exclude: The American Academy of Pediatrics emphasizes that new progressive facial asymmetry may be the first sign of an intracranial process requiring urgent attention. 2, 3
- Requires contrast imaging: Isodense tumors and subtle masses are missed on non-contrast studies. 1
Immediate Clinical Assessment Required
Complete Facial Nerve Evaluation:
- House-Brackmann scale grading: Assess forehead movement, eye closure completeness, mouth symmetry at rest and with movement, and check for synkinesis or hemifacial spasm. 2, 3
- Distinguish incomplete palsy from structural asymmetry: Incomplete facial nerve dysfunction shows normal tone at rest with asymmetry only during voluntary movement. 3
Comprehensive Ophthalmological Assessment:
- Rule out strabismus with compensatory head posture: Check visual acuity, binocular alignment, extraocular muscle function, and fundoscopic examination, as compensatory posturing can mimic structural facial asymmetry. 2, 3
Complete Cranial Nerve Examination:
- Beyond facial nerve alone: Test all cranial nerves, motor and sensory function throughout, and evaluate cerebellar function. 2
Structural Facial Analysis:
- Midline vertical alignment: Evaluate through glabella, nasal dorsum, philtrum, and menton; check for left-right differences in facial width, orbital level, and alar base position. 2, 6
- Cheek flattening or midface slanting: Suggests category (f) asymmetry requiring more extensive workup. 2, 6
Cardiac and Renal Screening:
- If ACF is suspected: Obtain echocardiogram and renal ultrasound to screen for associated congenital malformations, as ACF is a marker for cardiac defects and renal agenesis. 4
Immediate Specialty Referrals
- Pediatric neurology: For evaluation of possible intracranial or neurological causes of progressive facial asymmetry. 2, 3
- Pediatric ophthalmology: For comprehensive eye examination to rule out strabismus with compensatory head posture. 2, 3
- Pediatric plastic surgery or craniofacial surgery: If congenital malformations such as hemifacial microsomia are identified. 2
Critical Pitfalls to Avoid
Never assume benign structural asymmetry without contrast-enhanced neuroimaging: The American Academy of Pediatrics warns against this assumption, as progressive facial asymmetry in children requires prompt evaluation. 2, 3
Do not delay evaluation based on "dynamic-only" asymmetry: Asymmetry only with smiling does not exclude serious pathology—it specifically suggests incomplete facial nerve dysfunction. 3
Distinguish true anatomical asymmetry from functional asymmetry: Strabismus with compensatory head posture can mimic structural facial asymmetry and must be excluded. 2, 3
Do not miss ACF and fail to screen for associated malformations: ACF is easily mistaken for facial palsy but is a critical marker for cardiac, renal, and skeletal defects requiring screening. 4
Follow-Up Monitoring
Close monitoring of progression is essential: Conditions like hemifacial microsomia show increasing asymmetry with growth, and repeat imaging may be necessary if symptoms progress or change. 2, 3
Urgent reevaluation triggers: Clinical changes including regression of motor skills, loss of strength, or concerns with respiration or swallowing should prompt immediate reassessment. 2, 3