Sebaceous cysts arise from obstructed sebaceous glands; the contents consists of epithelial cells, fat, and cholesterin. They sometimes calcify. They spread in the subcutaneous tissue, stretching and raising the skin above and causing atrophy of the hair bulbs, but do not involve the epicranial aponeurosis below. In removing them, if they have never been inflamed, they can readily be turned out through a slit in the skin. The subaponeurotic space will not be opened, therefore their removal is not often followed by bad results.

Fig. 9.   Sebaceous cyst of scalp.

Fig. 9. - Sebaceous cyst of scalp.

Fig. 10.   Meningocele.

Fig. 10. - Meningocele.

Encephalocele is a tumor formed by a protrusion, through the skull, of the membranes of the brain, containing brain matter and cerebrospinal fluid.

Meningocele, or a tumor containing the meninges of the brain and cerebrospinal fluid, is more rare in the skull than is the case when the spine is affected. It protrudes through an unossified part of the skull, and, according to Sutton, two-thirds of the cases occur in the occipital region, between the foramen magnum and torcular Herophili. He characterizes it as a hydrocele of the fourth ventricle, and says that nine out of ten cases die if operated on. The next most frequent seat for meningocele is at the root of the nose (Fig. 10).

Cephalhydrocele is the name given to a pulsating tumor communicating with the interior of the skull through a traumatic opening. It contains cerebrospinal fluid.

Dermoid tumors occur in the median line and, according to Sutton, are most common over the anterior fontanelle and external occipital protuberance. They often have a thin pedicle attaching them to the dura mater and may grow either inside or outside the skull. They are formed by an inclusion of some of the tissue of the ectoderm by the bones as they approach from each side to ossify and unite in the median line.

A congenital tumor located at the root of the nose is probably an encephalocele; one located at the anterior fontanelle is probably a dermoid; a tumor in the occipital region may be either, but a dermoid is apt to be higher up than an encephalocele.