HYDROCEPHALUS.
Definition.—Hydrocephalus means an accumulation of serous fluid within the cranial cavity. The condition is fre quently spoken of as dropsy of the brain, or as "water on the brain," and may occur as an acute or chronic affection. The location of the fluid varies,' but is more frequently found within the cere bral ventricles than outside the brain or between its membranes.
Varieties.—The term "internal hydro cephalus" is applied expressly to chronic hydrocephalus usually congenital in origin, and when the word hydrocephalus is used without qualification it is this variety of the disease which is univer sally meant. Hydrocephalus may be primary, or secondary to some other dis ease.
Acute hydrocephalus is nearly always secondary to basilar meningitis, while chronic hydrocephalus is more fre quently primary, and very often con genital; it also often develops after birth without any apparent antecedent cause. Hydrocephalus has also frequently been classified as congenital and acquired; but since many of the cases, apparently be ginning after birth, really owe their origin to the same obscure causes which determine the congenital cases, it would seem better to regard the condition as acute or chronic. and as primary or sec ondary.
I. Acute Hydrocephalus. Definition. — Acute hydrocephalus means an effusion into the ventricles or within the membranes of the brain, as the result of an inflammation of the pia mater usually, either simple or tuber cular, or it may result from other inter cranial or systemic organic disease.' Symptoms.—The symptoms of acute hydrocephalus necessarily depend for their mode of development on the cause producing the effusion, and, as menin gitis of sonic grade is the most frequent cause, the signs of this disease very often precede and accompany those dependent upon the intracranial effusion. In other cases arising from gradual mechanical obstructions to the return venous circu lation, the onset of symptoms indicative of ventricular dropsy may be most diffi cult to determine; so that, especially if other serious illness—such as summer diarrhoea of infancy or one of the spe cific fevers—complicate the case, the diagnosis may be conjectural or even im possible. In such cases the meningeal affection sometimes runs a subacute course and gradually subsides, leaving an effusion which may, in rare cases, be absorbed again, but which more usually tends either to remain stationary or to slowly increase in amount until the char acteristic physiognomy of the hydro cephalic head is developed, and more or less permanent injury to the brain re sults, although such patients may sur vive for years in fair health.
Commonly, however, the signs of acute hydrocephalus appear during the course of one or other of the conditions to be referred to under etiology. When the primary disease is acute non-tubercular basal meningitis, the child stricken with this disease is apt to be fretful, irritable, restless, and sleepless, for from a few days to a week or two. Headache is another early symptom, and is usually combined with intolerance of a bright light. while the face is flushed and the anterior fontanelle pulsates strongly. At this early period there may also be stra bismus of irregular degree. Vomiting is frequently an early symptom, and may be an extremely marked one. The tem perature is that of moderate fever, but in severe cases there may be hyperpy rexia during the first two or three days or even longer. The pulse is in some cases distinctly slow and rather full, but in others much accelerated in rate and small in volume, or these conditions of the pulse may vary or alternate. The respiration is often shallow and irreg ular, and, after actual ventricular effu sion has occurred in sufficient amount to cause compression of the brain, Cheyne Stokes respiration is frequently noted, especially in the later stages of the dis ease. According to the severity of the cause producing the effusion coma de velops slowly or suddenly, with twitch ings and rigidity of a limb, or of all the limbs. This tremor and stiffness of the muscles may include the neck and spinal muscles, and twitching movements of the facial muscles or of the head are very com mon. In the rapidly-fatal cases the coma deepens, the pulse and respiration pro gressively fail. The face is void of ex pression, the eyes present marked con traction of the pupils, with occasional irregular movements of the ocular mus cles, convulsions may occur and be re peated many times, and the little patient dies from failure of the respiration and of the heart's action.