Definition: Spectrum of congenital structural forebrain anomalies defined by degree of frontal lobe fusion.
Depending upon the grade of separation, classified as lobar, semilobar and alobar type.
Epidemiology:
Age: Presents in infancy
Sex: male : female = 1.4 : 1
Clinical severity relates to degree of hemispheric and deep gray nuclei non-separation.
Anomalies associated with holoprosencephaly: Developmental field defects (extensive midline / schisis abnormalities); midline facial clefting, single central incisor, premaxillary agenesis.
\'Face predicts the brain\': severe midline anomaly = severe holoprosencephaly.
Sylvian angle of Barkovich is the key to understanding neuroanatomic abnormalities.