Meningoecie is a rarer condition and is difficult to distinguish from the above-mentioned variety. The defect in the bone is usually smaller. Nervous symptoms. particularly atrophy of the optic nerve, are entirely wanting. Horsley suggests the original expedient of determining the presence of reacting cerebral substance by means of irritation with the electric current.
The prognosis of hernia of the brain is unfavorable inasmuch as chil dren with large tumors not infrequently die from secondary infection of the tumor. The surgical treat ment of these conditions has been greatly perfected during recent times (v. Bergmann) and, in the case of hernias situated in the nasal region, consists ill the complete removal of the protruding sac. When the hernia is situated in the occipital region, the sac is opened and the pro truding portion of the brain replaced. The opening in the skull may be closed by an osteo plastic °per a tion or with a Frankel celluloid plate. If the pressure on the brain is severe, lumbar puncture is indicated (Preisich).
(b) Hernia of the s p in al cord. (Spina Bifida.) Hernia of the spinal cord or spina bifida has far greater clinical importance than hernia of the brain. It represents the most frequent malformation of the central nervous system in children (according to Demme, the incidence is one in 630 births) and has been exhaustively treated in the literature. Our know-ledge in regard to these conditions has been greatly extended during the past few years by the important investigations of v. Recklinghausen, which were followed by the valuable contributions of Aluseatello, Hildebrandt, Bayer, Bockenheimer, de Ruyter, Wieting, Katzenstein, and Many others.
Spina bifida results fron) failure of the medullary groove to unite at a certain point. This union normally takes place during the early stages of embryonal life. The bony, muscular, fascial and cutaneous coverings, either as a whole or in individual layers, take part in this failure to unite. In order that the contents of the vertebral canal may protrude through this opening there must be a collection of fluid at the corresponding point, hence, tile contents of the hernia are always fluid in a typical case of spina bifida. As in the case of hernia of the brain, several varieties of spina bifida are distinguished according to the contents of the tumor: ruyelocele (or myelonteningocele), royelo cystocele and meningocele.
In myelocele the medullary tube fails to unite posteriorly, and that portion of tbe spinal cord which remains uncovered is forced out back ward by a ventral effusion. This represents the most severe form of hernia of the cord and, as not only the spinal marrow itself but the spinal meninges, the bone and the external skin remain uncovered, the invaginated mass of spinal marrow is pushed directly through the opening to the surface of the body, and, after undergoing marked changes, forms the dome of the hernial sac. It appears as an oval, dark red, spongy, vas cular layer or zona medulloras enlosa, containing the remains of nerve elements and giving origin to the altered spinal nerves which enter the vertebral canal. Since the spinal marrow somewhere in its course, say in the dorsal por tion, undergoes this change, it is evident that both the cerebral and the spinal portions of the spinal marrow must open into the pathologically altered mass and, as a matter of fact, both the afferent and the efferent openings of the central canal can be found in the pole of the hernial sac. Below the zona medullova8culo8a, toward the base of the tumor, we find a broader, pearly gray, deli cate vascular portion resembling the serous coat of the intestine— the zona epithelioserosa, which genetically corresponds to the protruded pia. The portion near the base of the tumor consists of skin with dilated vessels and covered with numerous hairs, and is called the zona der_ inatica. This external form of myelocele, which is very important from a developmental standpoint, is rarely encountered in the typical form here described, because the coverings of the spina bifida as tbc result of intra-uterine maceration and infection occurring soon after birth, are converted into an ulcerated surface, or the hairy portion may proliferate and the entire sac becotne covered with epidermis. 111yelo cele is found most frequently in the lumbosacral, more rarely in the cervical region of the spinal marrow. Paralytic symptoms are most marked in this form of spina bifida.