Introduction: Given the multiple permutations in midline craniofacial malformations, classification has been difficult and disjointed. We believe that the median craniofacial malformations should be studied from an embryologic point of view. With tissue agenesis and holoprosencephaly at one end (the hypoplasias), and frontonasal hyperplasia and excessive tissue (the hyperplasias) at the other end, median anomalies with normal tissue volume (dysraphias) occupies the middle portion of the spectrum.

Method: A review of 35 years of midline craniofacial anomaly cases was performed. Data from this review and prior descriptive classifications and terminology for median craniofacial dysplasia was used to formulate our new classification system based embryopathogenesis and degree of severity.

Results: Median craniofacial dysplasia patients (n=84) were divided into three main categories: I- Median Craniofacial Hypoplasia (tissue deficiency or agenesis) (n=31); II- Median Craniofacial Dysraphia (normal tissue volume but clefted) (n=34); III- Median Craniofacial Hyperplasia (tissue excess or duplication) (n=19). Under each division further subclassification were used to clarify the specific anomalies (Table 1).

Conclusion: In the past the classification of median craniofacial dysplasia has been convoluted and confusing. Our revised classification system offers a more precise system that we hope will simplify diagnosis and the discussion of treatment plans.

SUBCLASSIFICATION	DESCRIPTION
I. Median Craniofacial Hypoplasia	Tissue Deficiency
A.     Holoproencephalic spectrum (alobar brain) 1.     Cyclopia 2.     Ethmocephaly 3.     Cebocephaly 4.     Primary Palate Agenesis	Single holistic brain with midline facial hypoplasia or agenesis. Four subclassifications: cyclopia, ethmocephaly, cebocephaly, Primary palate agenesis.
	1. Single eye in a single orbit, arhinia with proboscis often located above the single orbit and microcephaly
	2. Severe hypotelorism but separate orbits. Arhinia with proboscis located in between the orbits
	3. Severe hypotelorism. Proboscis-like rudimentary nose.
	4. Premaxillary segment missing of hypoplastic
B.     Median cerebrofacial hypoplasia (lobar brain)	Separate lobes to brain but with midline cerebral malformation; Midline facial hypoplasia.
C.     Median facial hypoplasia	Midline facial hypoplasia without gross cerebral involvement
D.    Microforms of median facial hypoplasia	1. Binder anomaly (maxillonasal dysplasia)
	2. Central maxillary incisor anomaly
	3. Absent Upper Lip Frenulum
II. Median Craniofacial Dysraphia	Normal tissue volume but clefted
True Median Cleft	Isolated cleft of the upper lip or abnormal split between the median globular process. It can be an incomplete or complete form
Anterior encephalocele	Cystic malformation in which central nervous structures are abnormally displaced or herniated through a defect in the cranium.
III. Median Craniofacial Hyperplasia	Tissue excess or duplication. All forms of excess tissue starting from just thickened or duplicated nasal septum to the more severe forms of frontonasal dysplasia.