The same is true of certain diseases which cause, at times, enlargement of the bronchial glands, and thus, by press ure on the venom innominatm, obstruct the venous circulation of the brain, re sulting in passive congestion and effu sion of serum from the engorged blood vessels. Acute hydrocephalus has also been frequently noted in connection with exhausting diseases, like severe cases of scarlet fever, typhoid fever, and prolonged diarrhoea of children, espe cially that occurring in summer.
Two cases, in children, of very marked hydrocephalus, with convulsions, spas modic rigidity of limbs, exaggerated knee-jerks, and total blindness. Gastro intestinal disturbance was in each case the starting-point of the affection. Mar fan (Sem. 1\16d., Aug. 21, '96).
Four cases of acute idiopathic internal hydrocephalus. Idiopathic acquired in ternal hydrocephalus is a disease sari genenis; the fulminating form may re cover, but the slower, insidious form is fatal. The disease is produced by ex posure to cold, and is to be looked upon as a vasomotor reflex neurosis. Heiden haiu (Berliner klin. Woch., Dec. 4, '99).
In the latter class of cases the effusion is partly the result of the actual wasting of the brain, which favors passive con gestion of the organ, and is also due, in part, to the great weakness of the circu lation, which is a special feature of pro tracted cases of infantile summer diar rho2a. Syphilitic meningitis may also be accompanied by an acute effusion into the ventricles, and in all of these cases a careful study of the family history, and a very critical examination of the pa tient, should be made so as to discover, if possible, other evidences of the exist ence of syphilis.
Syphilitic hereditary hydrocephalus is divisible into cases in which the hydro cephalus is the only sign of congenital disease; eases in which it follows on specific cerebral symptoms produced by a thickened ependyma. The eruption and other symptoms of congenital syph ilis may appear some weeks before, simul taneously with, or some time after, the hydrocephalus. In the last ease the hydrocephalus is the first symptom of hereditary syphilis. Of 170 eases col lected by E. Fournier, 5 were improved and 6 cured by specific treatment; the rest died. Personal case reported in which a successful result was obtained by means of specific measures continued one year. Audeoud (Rev. Med. de la Suisse Rom., Jan. 20, '99).
Finally, certain writers have reported cases of so-called essential dropsy of the brain, in which there could be found no anatomical lesion to explain the effusion. No case of acute effusion within the cranium should, however, be put into the last category, unless a careful and complete post-mortem fails utterly to re veal a pathological lesion, and the diag nosis of acute essential dropsy during life is certainly a wholly impossible one. Practically acute intercranial effusion of serum is more frequently seen as the re sult of tubercular or simple leptomenin gitis than from the other conditions above enumerated. (Acute hydroceph
alus and tubercular meningitis are often used as synonymous terms, but, in view of the many other conditions which oc casionally give rise to the former, it would be well to discontinue such use of these terms as misleading to stu dents.) Occasionally intracerebral haemor rhage may result in the formation of a cystic accumulation of serum within the membranes of the brain or between them and the skull itself. Pachymeningitis may also cause a localized collection of serum. In such cases of localized cystic collections there is very apt to be marked pressure thereby of the subjacent convo lutions. The amount of fluid present in any case of acute hydrocephalus is very small in comparison with the very large amount usually present in chronic hydro cephalus, and very rarely exceeds four or five ounces. When acute hydrocephalus arises from inflammatory disease of the membranes of the brain, the meningitis is commonly basilar. This is particularly true of the simple and tubercular menin gitis of children, while cases occurring in adult life frequently involve the mem branes over the convexity of the brain as well. Leptomeningitis as a cause of acute ventricular effusion is most fre quent before the end of the sixth year, and more often arises in subjects debili tated by previous disease, or by poor hygienic and social conditions.
Pathology. — Post-mortem examina tion of the brain in acute hydrocephalus of inflammatory origin reveals usually a basilar leptomeningitis, which may be simple, tubercular, infective, or syphi litic in origin, with an excess of fluid in the ventricles, causing a marked dilata tion of them, while the substance of the hemispheres presents appearances due largely to the increased intracranial pressure. This intracranial tension often partly expels the blood from the vessels, especially during the last hours of life; so that at the post-mortem the brain substance may look armnic, especially over the vertex and throughout the sub stance of the hemispheres. In cases of simple leptomeningitis the naked-eye appearances of the pia at the base of the brain will rarely present marked evi dences of the intense hyperemia existing during life. The ventricles are dis tended with a slightly-opaque or turbid serum, while the choroid plexus is over distended with blood, which may also be extravasated in punctiform patches in their immediate vicinity. The micro scope shows extravasation of leucoeytes along the lines of the blood-vessels and distending the perivascular sheaths, and also reveals minute capillary haemor rhages, pus-cells, and in some cases com pound granule-cells, depending largely upon the duration of the disease. The cerebral substance in some cases may contain areas of softening, but the rule is to find no such lesions, and, with the exception of changes in shape from pressure, the convolutions may be nor mal.