Semilobar Holoprosencephaly: Capacious Anomaly in the Cephalad

The holoprosencephalies (HPEs) are a group of disorders that are characterized by a failure of differentiation and midline cleavage of the prosencephalon, which usually occurs between days 18 and 28 of gestation. HPE has been divided into three subcategories based on the structural malformation: alobar, semilobar, and lobar HPE. Middle interhemispheric variant (MIH) or syntelencephaly is also considered as a milder variant of HPE. It is estimated to occur in 1/16,000 live births and 1/250 conceptuses. HPE is caused by genetic factors or environmental factors and teratogens. Clinical presentation depends on the severity of the malformation. Severe cases are usually associated with facial abnormalities like hypertelorism or midline facial clefts. HPE is diagnosed prenatally by ultrasound and MRI. Treatment of HPE is supportive and symptomatic. The clinical outcome depends on the severity of HPE and associated medical and neurological complications.