Congenital Midline Nasofrontal Masses

Midline nasofrontal masses are due to faulty regression of the midface dural diverticulum during embryologic development. The differential diagnosis includes:

• Epidermoid and dermoid cysts
• dermoid  
• ectoderm + skin appendages
• usually midline and tend to occur at the glabella
• epidermoid
• ectoderm without skin appendages
• usually paramidine
• Nasal gliomas
• not a neoplasm
• cerebral heterotopia
• can be intranasal (lateral nasal wall, middle turbinate, nasal septum) or extranasal (usually at glabella, +/- overlying skin telangectasia)
• T1WI - isointense/hypointense to gray matter
• T2WI - hyperintense to gray matter
• Encephaloceles
• herniation of intracranial content through a skull defect with a persistent connection to the subarachnoid space
• high prevalence of associated intracranial abnormalities
• intracranial cysts, callosal agenesis, interhemispheric lipomas, facial clefts, schizencephaly
• usually isointense to gray matter on all MR sequences 
• may be hyperintense on T2WI due to gliosis

REFERENCES
Lowe LH, Booth TN, Joglar JM, et al. Midface anomalies in children. Radiographics 2000;20:907-22.