Harris C P, Townsend J J, Carey J C
Department of Pathology, University of Utah, Salt Lake City.
Am J Med Genet. 1993 Jul 1;46(6):694-9. doi: 10.1002/ajmg.1320460620.
Acalvaria is a rare malformation usually regarded as a postneurulation defect. It consists of absence of the calvarial bones, dura mater and associated muscles in the presence of a normal skull base and normal facial bones. The condition is frequently confused by prenatal ultrasonography with anencephaly or an encephalocele. Whereas the cerebral hemispheres are absent in anencephaly, the cranial contents in acalvaria are generally complete, though some neuropathological abnormality is often present. The presumed pathogenesis of acalvaria is faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in absence of the calvaria but an intact layer of skin over the brain parenchyma. We describe 2 cases of acalvaria, one misdiagnosed ultrasonographically as an occipital encephalocele prenatally. The brain in one fetus demonstrated semilobar holoprosencephaly and micropolygyria, but in the other, was structurally and histologically normal with the exception of hydrocephalus.
无颅骨畸形是一种罕见的畸形，通常被视为神经胚形成后的缺陷。它表现为在颅底和面部骨骼正常的情况下，颅骨、硬脑膜及相关肌肉缺失。这种情况在产前超声检查中常被误诊为无脑儿或脑膨出。无脑儿中大脑半球缺失，而无颅骨畸形的颅内容物通常是完整的，尽管常存在一些神经病理学异常。无颅骨畸形的推测发病机制是膜性神经颅迁移异常，而胚胎外胚层位置正常，导致颅骨缺失，但脑实质上方有完整的皮肤层。我们报告2例无颅骨畸形病例，其中1例在产前超声检查中被误诊为枕部脑膨出。1例胎儿的脑部显示半侧叶全前脑畸形和微小多脑回，但另1例除脑积水外，结构和组织学正常。
