Cephaloceles

Javad Towfighi MD (Dr. Towfighi of Penn State University has no relevant financial relationships to disclose.)
Harvey B Sarnat MD FRCPC MS, editor. (Dr. Sarnat of the University of Calgary has no relevant financial relationships to disclose.)
Originally released October 5, 1995; last updated August 17, 2017; expires August 17, 2020

This article includes discussion of cephaloceles, encephalocele, exencephalocele, exencephalus, hernia cerebri, hydranencephalocele, atretic cephalocele, cranial meningocele, cranium bifidum, encephalocystocele, encephalomeningocele, frontoethmoidal cephalocele, interparietal cephalocele, lateral temporal cephalocele, nasal cephalocele, occipital cephalocele, orbital cephalocele, parietal cephalocele, sincipital cephalocele, transethmoidal cephalocele, and transsphenoidal cephalocele. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

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.

Key points

 

• 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.”

 

• They are categorized according to the site of the skull defect.

 

• They are often sporadic, but the occipital form may be part of a genetic malformation syndrome.

 

• Most cephaloceles and associated malformations are treated by surgery.

 

• 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 (Ballantyne 1904). 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 (Ballantyne 1904). 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 (Friede 1989). "Cranium bifidum" describes the bony defect only. "Exencephalus" is confused with "exencephaly," which represents an earlier stage of anencephaly (Warkany 1971). The term "exencephalocele" is also confusing and should be avoided. Among these, the term "cephalocele" appears to be the most appropriate (Ballantyne 1904; David 1993). This term denotes 2 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.

Diminutive forms of cephalocele appear as small noncystic subcutaneous nodules and are often of no clinical significance. These forms have been referred to under a variety of terms including "occult," "rudimentary," "abortive," "sequestrated," and "atretic" encephalocele or meningocele of scalp (Yokota et al 1988; Bale et al 1990; Martinez-Lage et al 1996; Patterson et al 1998). The other terms used for these subcutaneous lesions include "brain tissue heterotopia," "glial heterotopia," and "glioma" in scalp and nasal regions (Commens et al 1989; Yeoh et al 1989).

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