Head & Neck
Sinonasal Anatomy & the OMC: Clear the Floor First
Fellowship-level neuroradiology teaching by E. Brooke Schrickel, MD. Open this topic in the interactive reading room →
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Core clinical idea
On any superior nasal cavity mass in a child, clear the floor of the anterior fossa (cribriform/fovea ethmoidalis) before calling it a polyp — it may be an encephalocele or communicate intracranially via a dermal sinus, turning a routine biopsy/polypectomy into a CSF leak. The embryology just puts these lesions in predictable places; the safety move is the skull-base check.
Bottom line
Pediatric sinonasal masses sit in embryologically predictable places — and the superior nasal mass gets its anterior skull base cleared before anyone calls it a polyp.
Core workstation questions
- Is the cribriform/fovea ethmoidalis intact, or is this mass continuous with an anterior fossa defect (encephalocele/dermal sinus)?
- Is the obstruction anterior (nasolacrimal mucocele, pyriform aperture stenosis) or posterior (choanal atresia)? Bilateral = neonatal airway emergency?
- For choanal atresia: bony or membranous?
- Is there a CNS flag — mega-incisor, holoprosencephaly, extensive facial clefting — that mandates a brain look?
- For a midline dorsal lesion: is there a tract to the foramen cecum that must be resected in full?
What changes reporting / management
- For a superior nasal mass, prove the anterior fossa floor is intact; a defect raises encephalocele/intracranial communication and should halt blind transnasal biopsy/resection.
- Trace a nasal dermal sinus/dermoid to the foramen cecum and report how far the tract extends, since the surgeon must resect it in full to prevent recurrence/infection.
- Frame bilateral anterior nasal obstruction (mucocele, bilateral choanal atresia) in a newborn as an obligate-nasal-breather emergency; state bony vs membranous for choanal atresia.
- Use CNS flags (central mega-incisor, holoprosencephaly, midline facial clefting) to mandate a dedicated brain evaluation.
Practical traps
- Biopsying or resecting a superior nasal mass that is encephalocele/glial heterotopia or has an intracranial tract.
- Calling glial heterotopia a 'nasal glioma'/neoplasm (it is heterotopic glial tissue, often gliotic, may not image like brain).
- Missing the mega-incisor cue with pyriform aperture stenosis and not evaluating for holoprosencephaly.
- Failing to specify bony vs membranous choanal atresia, the surgeon's actual question.
Teaching pearls
- Superior nasal mass = check the cribriform/anterior fossa floor before you call it benign — it might be brain.
- 'Nasal glioma' is heterotopic glial tissue, not a tumor.
- A nasal dermal sinus must be traced to the foramen cecum and resected in full.
- A central mega-incisor with pyriform aperture stenosis sends you to look for holoprosencephaly.
- Bilateral anterior nasal obstruction in a newborn is an obligate-nasal-breather emergency.
- Bony vs membranous choanal atresia is the answer the surgeon actually needs.
Teaching visuals
Source lectures
- Sinonasal Imaging: Anatomy and Developmental Lesions
Educational material for radiology residents and neuroradiology fellows. Nothing here drives individual patient care, and it contains no patient data.