Cranial and Spinal Dysraphisms

Abstract

The term cranium bifidum is used to designate a defective closure of the skull by analogy with that of its spinal counterpart (spina bifida). Both malformations are regarded as neural tube defects (NTD); however, only anencephaly is a true NTD. The term encephalocele or meningoencephalocele designates a protrusion of any of the intracranial contents through a congenital defect in the skull, whether at the cranial vault or at the base [1, 3, 4, 7]. An encephalocele includes brain parenchyma (Figs. 7.1.1–7.1.3), while a cranial meningocele (Fig. 7.1.4) contains only cerebrospinal fluid (CSF) and is lined by arachnoid [1, 3, 4, 7]. In certain cases, encephaloceles may comprise parts of a ventricle or choroid plexus [1, 3, 4, 7]. Atretic cephalocele (Fig. 7.1.5) refers to a small-sized midline subscalp lesion that contains no cerebral tissue but neural remnants [5, 7, 10]. There is no clear-cut limit to separate the diverse clinical forms that constitute the spectrum of cranium bifidum. At present, the terms cephalocele and encephalocele are used interchangeably to encompass all these lesions [7]. Table 7.1.1 summarizes the definitions of the spectrum of cranial congenital defects, and Table 7.1.2 classifies cephaloceles into four main types according to their composition.