Holoprosencephaly Syntelencephaly 2022-01-17T17:19:34Z This condition differs from holoprosencephaly (HPE) in that the midline fusion in syntelencephaly is complete but segmental, while the structural brain anomalies seen in the HPE spectrum progress smoothly in severity in a posterior to anterior fusion. Syntelencephaly is a rare malformation that consists of an abnormal midline connection of the cerebral hemispheres in the posterior frontal and parietal regions, with interhemispheric separation of the basal forebrain, anterior frontal lobes, and occipital regions.