8.17 Congenital Midline Nasal Masses
Key Features
The most common congenital midline nasal masses are gliomas, encephaloceles, and dermoids.
The most common of these is the dermoid, derived from ectodermal embryonic tissue.
A glioma consists of central nervous system (CNS) tissue at the nasal dorsum; it is congenital and not a true neoplasm.
Meningoceles and encephaloceles do communicate with the ventricles and contain cerebrospinal fluid (CSF).
Teratomas are true neoplasms arising from totipotent cells; half of all head and neck teratomas occur in the nose.
Gliomas, meningoceles, encephaloceles, dermoids, and teratomas exist in the differential diagnosis of the congenital midline nasal mass. A dermoid cyst is a congenital benign neoplasm containing keratinizing squamous epithelium and adnexal skin structures, may be located anywhere from the columella to the nasion, and often presents as a dimple on the nasal bridge. The dermoid may involve only skin and nasal bone, or it may have a true dural connection. Nasal gliomas lack a direct connection to the CNS and contain heterotopic glial elements in a fibrillar stroma, of varying growth rate. Encephaloceles are continuous with the CNS. Sincipital encephaloceles present in the nasal dorsum or forehead region, basal encephaloceles in the nasopharynx. Encephaloceles may include meningoceles (containing only meninges), encephalomeningoceles (containing brain also), and encephalomeningocystoceles (including part of the ventricular system). Midline nasal masses should never be biopsied in the outpatient setting or without prior imaging studies.
Epidemiology
Congenital midline nasal masses occur in 1 in 20 to 40,000 live births. Ten percent of dermoids occur in the head or neck, and 10% of these occur in the nose. Encephaloceles occur in 1 in 1,250 to 2,000 live births; 40% have other abnormalities. Occipital encephaloceles are most common in North America (75%), although sincipital ones are most common in Southeast Asia.
Clinical
Signs
Dermoids are typically anywhere along the midline of the nose and are firm, noncompressible, and nonpulsatile. A nasal dermoid sinus or cyst presents with a dimple containing a hair follicle. Rarely, the nasal base is widened. Encephaloceles are soft, bluish, compressible, pulsatile, and may transilluminate. Gliomas are smooth, firm, noncompressible, and nontransilluminating. All may be associated with a cranial defect, although this is most common with an encephalocele.
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