Ramakrishnan Sharanya, Das Joe M.
Grant Government Medical College and Sir JJ Group of Hospitals
Imperial College Healthcare NHS Trust, London
Holoprosencephaly (HPE) results from an incomplete midline cleavage of the forebrain (prosencephalon). It includes a wide spectrum of intracranial and craniofacial midline defects and a myriad of clinical manifestations, consisting of neurologic impairment and dysmorphism of the brain and face. It is the most common malformation of forebrain development. Evidence suggests that HPE can be present either sporadically or can have a syndromic association. The defect associated with HPE occurs at approximately 3 to 4 weeks post-conception (between day 18 and day 28 of embryonic life) and is a disorder of gastrulation. The HPE phenotype continuum has been divided into 3 categories by DeMyer and Zeman and modified by DeMyer. These categories include: This is the most severe and most common form (two-thirds of all HPE cases), characterized by a complete failure to partition the forebrain into the left and right hemispheres; this results in a single, centrally located ventricle. Partial forebrain cleavage Almost complete forebrain cleavage (syntelencephaly): A rare variant with an abnormal midline union of the posterior frontal and parietal lobes. : This rarest variant is mild, and the midline fusion is restricted to the telencephalon's septal or preoptic region.
前脑无裂畸形（HPE）是由前脑（端脑）中线不完全分裂所致。它包括一系列颅内和颅面中线缺陷以及众多临床表现，包括神经功能障碍和脑面部畸形。它是前脑发育最常见的畸形。有证据表明，HPE既可以散发性出现，也可以与综合征相关。与HPE相关的缺陷发生在受孕后约3至4周（胚胎期第18天至第28天之间），是一种原肠形成障碍。前脑无裂畸形的表型连续体已由德迈尔和泽曼分为3类，并由德迈尔进行了修改。这些类别包括：这是最严重和最常见的形式（占所有HPE病例的三分之二），其特征是前脑完全未能分成左右半球；这导致一个位于中央的单一脑室。部分前脑分裂几乎完全前脑分裂（融合性全前脑畸形）：一种罕见的变异型，额后叶和顶叶中线异常联合。：这种最罕见的变异型较轻，中线融合仅限于端脑的隔区或视前区。
