Congenital frontonasal masses: developmental anatomy, malformations, and MR imaging.

The newborn, infant, or young child who presents with a midline frontonasal mass often poses a diagnostic challenge to the clinician. The most pressing issue is whether the mass extends intracranially. The development of the frontonasal region or anterior neuropore is complex. Aberrant embryogenesis leads to three main types of anomalies: nasal dermal sinus, anterior cephalocele, and nasal glioma. Understanding the developmental anatomy of the anterior neuropore and postnatal maturation will serve the radiologist well when it comes to imaging frontonasal masses. Pitfalls particularly common to CT imaging interpretation include the evolving ossification of the frontal, nasal and ethmoid bones in the first year of life, morphology and size of the foramen cecum, and the natural intumescence of the anterior nasal septum. Determination of the presence of a connection between the frontonasal mass and the anterior cranial fossae is crucial in the imaging assessment and clinical management. In the case of the nasal dermal sinus, failure to appreciate the intracranial components of the malformation can lead to fatal meningitis. MR imaging is the modality of choice for assessing the pediatric frontonasal region. Its advantages include multiplanar imaging, distinguishing the interface among cartilage, bone, brain and fluid, diffusion imaging to detect epidermoid tumors, and the capacity to evaluate the brain for associated cerebral anomalies.