Sonographic Diagnosis of the Middle Interhemispheric Variant of Holoprosencephaly in the Prenatal Period

Abstract

Holoprosencephaly (HPE) is a disorder of development and separation of prosencephalic vesicles. The prosencephalon cannot be divided sagittally into the cerebral hemispheres, transversely into the diencephalon and telencephalon, and horizontally into the olfactory and optic spheres on during develepment. There are 3 main types of HPE: alobar, semilobar, and lobar. 1 The incidence is higher in abortions compared to live births (1/200-250 abortions and 1/10,000 live births). 1,2 Recently, middle interhemispheric variant (MIHV) or syntelencephaly, which is a milder form of the disease compared to these 3 main types, has been defined, and 6 articles in the literature reported that there are 11 MIHV cases diagnosed during the prenatal period. 3,4 MIHV is usually a milder variant with the characteristic sonographic findings of a single fused ventricle and absence of the cavum septum pellucidum (CSP). The separation of the posterior part of the frontal lobe and the parietal lobe is impaired in MIHV. The basal forebrain, anterior frontal and occipital lobes are normally separa-ted. 3,4 Etiology is multifactorial and most cases are sporadic. However, the disease has also been associated with teratogenic exposure, intrauterine infections, maternal metabolic diseases, genetic disorders such as chromosomal aneuploidies and single gene disorders. 5