MENINGITIS).
Chronic hydrocephalus, or "water on the brain," consists in an effusion of fluid into the lateral ventricles of the brain and depends upon congenital malformation or upon chronic inflammatory changes affecting the membranes. When the disease is congenital its presence in the foetus is apt to be a source of difficulty in parturition. It is, however, more often developed in the first six months of life ; but it occasionally arises in older children, or even in adults. The chief symptom is the gradual increase in size of the upper part.of the head out of all proportion to the face or the rest of the body. Occurring at an age when as yet the bones of the skull have not become welded together, the enlargement may go on to an enormous extent, the spaces between the bones becoming more and more expanded. In a well-marked case the deformity is very striking; the upper part of the forehead pro jects abnormally, and the orbital plates of the frontal bone being inclined forwards give a downward tilt to the eyes, which have also peculiar rolling movements.
The expansibility of the skull minimises destructive pressure on the brain, yet this organ is materially affected by the presence of the fluid. The cerebral ventricles are distended, and the con volutions are flattened. As a consequence, the functions of the brain are interfered with and the mental condition is impaired. The child is dull, listless and irritable, and sometimes imbecile. The special senses become affected as the disease advances ; sight and hearing are often lost. Hydrocephalic children generally sink in a few years; nevertheless, there have been instances of persons with this disease living to old age.
Various methods of treatment have been employed, but the results are uniformly unsatisfactory.