Holoprosencephaly
Holoprosencephaly is a brain malformation resulting from failure of prosencephalon (the forebrain of the embryo) to divide into two distinct cerebral hemispheres. It is the most common brain malformation with an incidence of 1:250 during embryogenesis and 1:16,000 among live births. It has four subtypes: alobar holoprosencephaly, semilobar holoprosencephaly, lobar holoprosencephaly, and a middle interhemispheric fusion variant (syntelencephaly). Alobar holoprosencephaly is the most severe form, and as the name implies, there is no separation of the cerebral hemispheres.
Moderate to severe cases generally have a poor prognosis. the mortality rate increases as follows, with 33% in the first 24 hours after birth, to 58% in the 1 month, to 50% between the 4 and the 5 months, to between 70% to 80% in the 1 year of life. The survival rate after 1 year of life is only around 29%. A very small number survive until adulthood. Mild to moderate cases typically survive till adulthood, but live with the accompanying complications.