The author reviews the various forms of cephaloceles (encephaloceles and cranial meningoceles) and their diverse clinical manifestations. He provides historical context, classification, and modern methods of diagnosis and treatment of these diseases. This article has been updated to include new approaches to the surgical management of such patients.
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• Cephaloceles are typically herniations of brain tissue with meninges (encephalocele) or meninges only (cranial meningocele) through a congenital skull defect, and they are classified among “neural tube defects.”
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• They are categorized according to the site of the skull defect.
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• They are often sporadic, but the occipital form may be part of a genetic malformation syndrome.
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• Most cephaloceles and associated malformations are treated by surgery.
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• Prognosis depends on the site, content of the sac, operability, hydrocephalus, and other associated malformations.
Historical note and terminology
The term cephalocele, in a restrictive sense, is defined as a protrusion of part of the cranial contents through a congenital opening in the cranium, typically covered with skin or mucous membrane. However, in a broad sense of the term, it has been used to include also the acquired traumatic and nontraumatic forms. This review is mainly concerned with the congenital form of cephalocele. The condition was first described by Forestus in 1590 (04). The first monograph on the subject was written by Corvenius in 1749 and was followed by a long series of papers on the various aspects of the disorder including the clinical features, pathology, incidence, pathogenesis, and treatment (04). Ballantyne's comprehensive morphologic study contributed significantly to the understanding of the pathology of the lesion and its classification. A variety of terms have been used to describe this congenital lesion. They include "hernia cerebri," "hydranencephalocele," "encephalocele," "cephalocele," "cranium bifidum," "exencephalus," and "exencephalocele." The term "hernia cerebri" should be reserved for acquired lesions. "Hydranencephalocele" is confused with "hydranencephaly," which represents a different congenital lesion (49). "Cranium bifidum" describes the bony defect only. "Exencephalus" is confused with "exencephaly," which represents an earlier stage of anencephaly (157). The term "exencephalocele" is also confusing and should be avoided. Among these, the term "cephalocele" appears to be the most appropriate (04; 33). This term denotes two specific types of lesions: herniation of brain tissue with the overlying meninges through a cranial defect (meningoencephalocele or encephalocele); and herniation of meninges without brain tissue (cranial meningocele). Today, the terms cephalocele and encephalocele are used almost interchangeably in the neurosurgical literature.
Mention should be made of the small, often noncystic subcutaneous nodules that, similar to cephaloceles, contain meninges with or without brain tissue but lack open communication with the cranial cavity. These lesions have been referred to under a variety of terms including "occult," "rudimentary," "abortive," "sequestrated," and "atretic" encephalocele or meningocele of scalp (165; 96; 118). The other terms used for these subcutaneous lesions include "brain tissue heterotopia," "glial heterotopia," and "glioma" in scalp and nasal regions (27; 164).