CEPHALOCELE (Congenital cerebral hernia.) At certain favorite places greater or smaller defects of the cranium are formed through which its contents protrude. The contents of the hernial sac may vary, and accordingly cephalocele can be divided into the following groups: 1. a small portion of the cerebral sac has prolapsed through the opening in the skull. The wall consists of cerebral masses and their covering meninges.
Meningocele.—Thc wall consists only of the internal cerebral meninges; parts of the brain substance itself are not demonstrable in the wall of the sac, although there may be some contained within the sac. The etiology is readily understood from the preceding explanation, so far as these still obscure biological processes are within our knowl 9 edge. Questions as to why there should be a prolapse or why the cranium should remain open at some places are still unanswered. To say that intra-uterine inflammatory processes, amniotic cords, excessive fluid pres sure in the interior of the sac, are responsible is only a makeshift. They may be a contributory factor, but how much of it is due to degenerative processes, family heredity, inferiority and disease of the parents, and whether the entire chain of deformity is not a normal reaction, are questions for future investigators to elucidate. The investigations of llertwig and others throw some light upon these points. These investigators were able to produce entirely analogous deformities on lower animals by impairing the health of the parental pair before procrea tion by chronic poisoning and by injuring the ovum.
The origin of these deformities is best explained by the opinion ad vanced by von Bergmann, who as sumes —as do Recklinghausen and Morian—that in every case there is a misturning of the cerebral sac. All other formations, including meningo cele, are of secondary origin. In meningocele the sae has undergone excessive thinning. The cerebral sub stance has been obliterated or not developed, or it has receded into the interior of the skull cavity during growth. The fine ependyma which lines the inside of the sac points to this origin. All these cysts communi
cate with the interior of the ventricle.
The duets may be traced through the pellicle with very fine probes, but they sometimes become entirely obliterated (Fig. 4).
This explanation is simple and logical, although there are various possible combinations of deformities which seem to throw doubt on the clearness and justification of the assumption.
Pathological Anatomy.—The protrusion has a predilection for cer tain regions of the cranium. Accordingly, we distinguish cephalocele which emanates from the facial skull, usually at the root of the nose, as anterior eephaloeele (Fig. 2), and cephaloeele which emanates at the occiput above the foramen magnum as occipital eephaloeele (Figs. 3 and 4).
Basal cephalocele, situated at the base of the skull, is much rarer, though possibly it is observed less frequently on account of its small size, as it might be taken for a pharyngeal cyst.
Anterior cephalocele is subdivided into naso/ronlal, protruding above the nasal bone; protruding in the inner canthus; and nasfi ellonoidal, appearing below the nasal bone. Occipital cephalocele is called superior or inferior according to whether it appears above or below the occipital protuberance.
There are other places in the skull where occasionally gaps may occur with prolapse of the meninges or cerebral substance, as for instance at the orbital margin or at the sutures.
The gap is generally round with sharp borders and the Jura merges into the periosteum of the external skull. Only the inner meninges, the arachnoid, and the pia accompany the cerebral protrusion. Frequently they are closely adherent to the external covering membrane at the top of the excrescence. The thinning and blending of the meninges and periosteum are dependent upon the pressure exerted on the covering tissues by the interior fluid. The tension of the fluid frequently changes, so that many of these cystic tumors look as if thev were ready to burst, especially when there is a considerable accumulation of fluid in the brain -sue Fig. 2).