DIAGNOSIS.—The distinction between meningeal hemorrhage and cerebral apoplexy is always difficult, and in the majority of cases impossible. Sudden pain in the head, vomiting, and lowering of the bodily temperature (the thermometer should be placed in the rectum), followed by loss of consciousness, are strongly suggestive of hemorrhage within the cranium, either cerebral or meningeal. If these symptoms are followed by coma and resolution without obvious paralysis, the diagnosis would be almost impossible between intra- and extra-cerebral extravasation. If the loss of consciousness be not complete, so that the presence or absence of paralysis can be ascertained, we can sometimes distinguish the situation of the hemorrhage. Right-sided hemiplegia, with paralysis of the face or tongue, or with aphasia, is most probably owing to hemorrhage or embolism somewhere in the left motor tract, and hence within the brain. If the absence of paralysis can be certainly ascertained, the probabilities are in favor of meningeal apoplexy. Convulsions affecting the face or limbs of one side would point to irritation of the cortical centres of those parts, and so far to extravasation on the surface of the brain (on the opposite side), as in Webber's case. Where the amount of hemorrhage is small it furnishes no diagnostic indications. In the case of new-born children the presumption is in favor of meningeal effusion.
PROGNOSIS.—If the effusion be considerable in amount, as indicated by prolonged coma with resolution, the issue is almost inevitably fatal, though life is occasionally prolonged for a surprising length of time. Slight hemorrhages are doubtless recovered from, but there are no means for their certain diagnosis.
TREATMENT.—The treatment, which is essentially the same as that for cerebral congestion, has for its object the arrest of the hemorrhage, and, if that can be effected, the absorption of the effused blood. In view of the former, the patient's head should be elevated and kept cool by the application of ice. Unless the bowels have previously been freely moved, saline laxatives, followed by enemata if necessary, must be given. The state of the bladder must be carefully attended to. Liquid nourishment alone, in moderate quantities at regular intervals, is permissible, with stimulants if there be signs of exhaustion. For the absorption of the effusion mild counter-irritation to the scalp and the administration of the iodide of potassium may be employed.
Congestion of the Cerebral Pia Mater.
The pia mater consists of two layers, separated by a loose connective tissue. The outer layer, being that which was formerly called the visceral layer of the arachnoid, is stretched smoothly over the convolutions of the brain without dipping into the sulci; the inner layer is closely connected with the surface of the brain, whose inequalities it follows. The two layers are more firmly united together over the convolutions than between them; in the latter situation the connection is loose, and the space which separates the surfaces is called the meshes of the pia. The membrane extends into the ventricles, investing the ependyma and the choroid plexuses, and over the medulla oblongata and spinal cord. In the normal condition it is loosely attached to the brain, from which it can be stripped off without loss of substance. The meshes of the pia, together with the ventricles, constitute a series of cavities connected with each other, containing a variable amount of cerebro-spinal fluid, and they communicate with the lymph-spaces surrounding the blood-vessels. Pressure within the cranial cavity, from congestion of the vessels or from the products of inflammation, is thus relieved in a measure by displacement of the cerebro-spinal fluid, which is driven out through the perivascular lymph-spaces.
Congestion or hyperæmia of the pia mater probably never occurs independently of that of the external surface of the brain, on account of the intimate vascular connection of the two. In the adult it can only exist to a limited extent, on account of the unyielding nature of the cranial walls and of the limited compensatory action of the cerebro-spinal fluid. In young children the incomplete ossification of the skull and the delicate structure of the vessels are more favorable to congestion.
ETIOLOGY.—The causes of hyperæmia of the pia mater are in the main the same as those of congestion of the dura.
SYMPTOMS.—Since congestion of the pia always coexists with that of the corresponding part of the external portion of the brain, it is impossible to separate the symptoms belonging to each. They are therefore usually included under the head of Cerebral Congestion, to which article the reader is referred.
PATHOLOGICAL ANATOMY.—Arterial hyperæmia of the pia is seldom discovered after death, the elasticity of the vessels causing transudation of the fluid part of the blood through their walls. Venous congestion of the pia is more frequently noticed, usually in connection with that of the dura, the sinuses with their accompanying veins being distended with blood, and in cases of long standing often containing thrombi. Simple hyperæmia of the pia being rarely or never fatal of itself, these appearances are usually accompanied by those of inflammation of the membrane or of the cortical layer of the brain (effusion of lymph or pus), or by hemorrhage.
TREATMENT.—In a case of suspected congestion of the pia the treatment would be the same as that of cerebral congestion.