Among the more significant and immediate symptoms are to be reckoned paræsthesiæ of the side about to be paralyzed, such as numbness or tickling. Headache of great severity is often, but not invariably, present. It has nothing characteristic about it, except that it may be different from those the patient has been in the habit of having, or may be of unusual severity, so that the patient says it is going to kill him. Such a headache in a person in whom there is good reason, from age, interstitial nephritis, or other symptoms, to suspect the existence of vascular lesions is likely to be an immediate precursor of a hemorrhage. Persistent early waking with a slight headache, which passes off soon after rising, is said by Thompson29 to be a somewhat frequent premonition. Vomiting is hardly a premonitory, but may be an initial, symptom, especially in hemorrhage of the cerebellum.
29 N. Y. Med. Record, 1878, ii. p. 381.
Reference is had in these statements chiefly to the ordinary form of cerebral hemorrhage. Of course if, during a leucocythæmia or purpura, large hemorrhages occur elsewhere, it may be taken as a hint that possibly the same thing may take place in the brain.
These signs of arterial disease must be considered as of the highest importance among the (possibly remoter) premonitory signs, not only of cerebral hemorrhage, but of the other lesions treated in this article. Atheroma and calcification of the tangible arteries place the existence of peri-endarteritis among the not remote possibilities. High arterial tension has already been spoken of in connection with etiology, and its presence should be sought for. An irregular and enfeebled cutaneous circulation has been spoken of as an indication of value.
OCCLUSION OF THE CEREBRAL ARTERIES may take place from several causes other than those which concern us here, as from the pressure of tumors or endarteritis, usually syphilitic. Thrombosis and embolism are grouped together from their great anatomical resemblance and their frequent coexistence, but the symptoms produced, although ultimately the same, are often different enough to make it necessary to bear in mind the fact that there is a distinction—that is, that embolism is rapid and thrombosis is slow.
A cerebral artery may be occluded from the presence of a plug of fibrin more or less intermixed with the other elements of the blood. This plug may have been formed in situ, and is then somewhat firmly attached to the walls of the vessel, and partly decolorized at its oldest portion, while on each side of it, but especially on the side away from the heart, it is prolonged by a looser and darker clot of more recent origin. This is a thrombus.
When the plug has been transported from elsewhere it is embolus.30 It may consist of various substances, as described in the article on General Pathology, but is usually of fibrin which has formed a thrombus or vegetation elsewhere, and, having been broken off, is carried by the blood until it comes to a place too narrow for it to pass, or where it lodges at the bifurcation of a vessel. The piece of fibrin thus lodged has a strong tendency to cause a still further deposition—that is, a secondary thrombus—which may progress until it comes to a place where the blood-current is too strong for the process to go on any farther. It may in such cases not be obvious at the first glance whether the whole process is thrombosis or whether it started from an embolus.
30 The Greek word εμβολος (εν, in, and βαλλω, to throw) signifies the beak or rostrum of a ship of war. Εμβολον signifies wedge or stopper, and would certainly seem the appropriate form to be adopted for anatomical purposes. As uniformity of nomenclature, however, seems more to be desired than etymological accuracy, the writer has conformed in this article to the general usage.
It is probable that a thrombus forming at one point in a cerebral vessel may break to pieces and its fragments be carried farther along, forming a number of small emboli. (See Capillary Embolism.) Embolism or thrombosis may take place anywhere in the brain or body generally, but has certain points of preference. Of these, the most usual in the brain is in the neighborhood where the internal carotid divides into the anterior and middle cerebral, or in either of these arteries, especially the middle, beyond this point. The plug may be situated in the carotid just before this point, or even as low down as its origin from the common trunk. Emboli lodge in this region, somewhat more often upon the left side. The brain is said to be third in the order of frequency with which the different organs are affected by embolism, the kidneys and spleen preceding it. It has been found that small emboli experimentally introduced into the carotids are found in much larger numbers in the middle cerebral than elsewhere. It is the largest branch, and most nearly in the direct line of the carotid. Position undoubtedly influences the point at which an embolus lodges, as it probably moves slowly along the vessels and along their lower side. It has been remarked that, on account of this course of the embolus, it is doubtful whether it can get into the carotid when the patient is standing, but it certainly can do so when he is sitting up; which, so far as the direction of the carotids is concerned, is the same thing. The frequency with which a hemiplegia is observed when a patient awakes in the morning may perhaps be accounted for by the position favoring the passage of an embolus into the carotid, which otherwise would reach organs more remote.
The vertebrals and basilar are not infrequently affected.