As the various forms of hydrocephalus nill bc discussed in this work in their appropriate places, we shall confine ourselves here to a description of congenital hydrocephalus.
Congenital hydrocephalus in the great majority of cases is internal; although, in view of the statements of Leon d'Astros, Heubner and Bokay, tbe occurrence of congenital external hydrocephalus which had been presiously denied, can no longer be called in question. In the latter form the brain is intact, usually somewhat diminished in size, and also contains an accumulation of fluid within the ventricles; the condition probably represents the remains of an intra-uterine meningitis. External hydrocephalus also occurs after intra-uterine shrinking cesses and in combination with defects and malformations of the brain.
Congenital internal hydrocephalus also suggests the previous exist ence of intra-uterine disease affecting the vascular apparatus, witb excessive exudation of fluid—either a hypersecretion of fluid from the chorioid plexus due to unknown eauses or actual inflammatory processes. If this eollection of fluid takes place at an early stage, the development of tbe brain is interfered with (see below; hydromicrocephalus); in that ease hydrocephalus has the same significance as arrested develop ment of the brain. In other cases the accumulation of fluid brings about atrophy of the already completely developed brain.
The causes of congenital hydrocephalus are by no means certain. Alcoholism, tuberculosis and nervous diseases on the part of the parents have been assigned. The influence of syphilis, which undeniably plays a part in aequired hydrocephalus, Is doubted in the ease of the congenital variety. Possibly the condition represents a parasyphilitic affection (see below). Hereditary hydrocephalus has been described and the disease may occur in several members of the same family.
The quantity of fluid in hydrocephalus may lie enormous (5 litres and uver; usually the quantity is about one litre). The fluid is watery and contains no cellular elements, and chemically corresponds to an indifferent saline solution; the low. pereentage of albumin and the large quantity of salt in the fluid are characteristic features. The greatly distended ventricles exert pressure on the mantle of the brain, eausing flattening of the convolutions, narrowing of the soft cerebral mass and, in severe cases, complete obliteration, leaving nothing but a thin layer which can be recognized only with the microscope. The basal ganglia
are often flattened; the cerebellum is altered and displaced (Chiari).
As ossification does not take place, the soft sleull is unable to resist the pressure of the fluid within the brain, it becomes enormously enlarged, the bones of the skull are attenuated, the sutures greatly widened, and the fontanelles bulge. The circumference of the head has been known to reach 50 and even 100 centimetres. in these cases the bones of the skull are widely separated and appear like islands in the connective tissue, which spans the fontanelles and sutures. The cranial veins are usually dilated, the skull is smooth and scantily covered witb hair. In contrast to the enormously enlarged skull, which projects on both sides of the head, the countenance appears diminutive, like a mere appendage. The eyes are usually dislocated downwards, bringing the upper border of the cornea into view. The expression iS staring and devoid of intelli gence and the movements of the eyes are usually restricted. The abnormal position of the eyes is probably due to the pressure of the fluid on the attenuated, unresisting orbital plates. Nystagmus, stra bismus, sluggishness of the pupils and atrophy of the optic nerve are sometimes present.
The mentality of these children ranges between extreme idiocy and normal intelligence. Most of the children are feeble-minded, apa thetic, and have more or less difficulty in speaking. Motor disturbances are usually well marked and manifest themselves in spasms, paresis, universal rigidity, tremors, awkward movements of the hands, etc. As the lower extremities are ahnost always more severely affected than the upper, walking is very much delayed; there is a tendency to cross ing of the legs and the gait is spastic. Sometimes, the spasms and paresis are more marked on onc side than on the other. The reflexes are increased. Aside from these motor disturbances, hydrocephalic children exhibit a peculiar indolence, a disinclination to exercise, which is enhanced by the difficulty of steadying the abnormally large and heavy head. Twitching of individual groups of muscles and general convulsions are by no means rare. Hydrocephalic children usually present a distinctly delicate appearance; they are pale, emaciated, with senile expression, cry a good deal and do not increase properly in weight. The appetite is not bad, but digestion is usually retarded.