Chronic internal hydrocephalus, on the other hand, is a comparatively common condition. It may be of congenital origin, or may develop in young rickety children, usually as a result of some chronic inflammatory process in the membranes at the base, the choroid plexuses, or the ependyma of the ventricles, causing obstruction to the outflow of blood through the internal cerebral veins of Galen. In the acquired form the communication between the ventricles and the sub-arachnoid space, by way of the foramen of Magendie, is obstructed, so that the cerebro-spinal fluid is pent up in the ventricles and gradually distends them. The pressure causes the head to enlarge, the fontanelles to bulge, and the bones to be separated from one another, the interval between the bones being occupied by a thin translucent membrane.
The cerebral tissue is greatly thinned out, but the cerebellum and cranial nerves usually remain unaffected.
The appearance of the patient is characteristic ([Fig. 200]). The enormous dome of the skull surmounts a puny and preternaturally old face; the eyes are pushed downwards and forwards by the pressure on the orbital plates, and the eyebrows are displaced upwards. The head rolls helplessly from side to side; the child moans and cries a great deal; and vomiting is often a prominent symptom. In most cases the intelligence is defective, and epileptic seizures and other functional disturbances of the brain may be present.
Fig. 200.—Hydrocephalus in a child æt. 31/2.
In mild cases, especially when associated with rickets or syphilis, recovery sometimes takes place, but in the majority the condition progresses, and death results either from convulsions or from some intercurrent disease. Few hydrocephalic subjects reach adult life.
Treatment.—Hydrocephalus being a symptom rather than a disease, no method of treatment which does not remove the primary cause can be permanently curative. Anti-syphilitic treatment should be tried in the hydrocephalus of infants and young children. The rachitic element, when present, must also be treated.
In congenital hydrocephalus, as there is no blocking of the passages at the fourth ventricle, the foramina being as a rule much larger than normal, no form of drainage is beneficial. Ligation of the common carotids, one some weeks after the other, has been successful in restoring the balance which normally exists between the secretion and absorption of the cerebro-spinal fluid (H. J. Stiles). In acquired hydrocephalus, puncture of the ventricles is sometimes followed by a remarkable improvement in the symptoms, and may even result in apparent cure. An exploring needle is introduced at the lateral angle of the anterior fontanelle, to avoid the superior sagittal (longitudinal) sinus, and from a half to one ounce of cerebro-spinal fluid withdrawn. This is repeated once a week for several weeks. Continuous drainage of the fourth ventricle through an opening made in the occipital region (Parkin), and the establishment of a communication between the ventricle and sub-arachnoid space (Watson-Cheyne), or between the sub-arachnoid space of the spinal cord and the peritoneal cavity, or the retro-peritoneal space (Cushing), have been tried, with little more than temporary benefit in the majority of cases. Operative treatment, if it is to do good, must be undertaken early, before permanent changes in the brain have taken place.
Micrencephaly.—This condition is due to defective development of the brain, and not to premature closure of the cranial sutures and fontanelles, and as the subjects of it are mentally deficient, and often blind, deaf and dumb, the removal of segments of the skull with a view to enable the brain to develop have proved futile.