Etiology.—This has been given in part under the heading VARIETIES.
The forms of verrucous and ulcerative endocarditis, yielding vegetations or other solid fragments that may become freed from their base, are the best-recog nized causes of embolism. It has been found that embolism of the brain occurs in 5 per cent. of cases of valvular disease, and that this occurs twice as frequently in females as in males.
Rheumatism, gonorrhoea, chorea, scar let fever, and septic processes of all kinds in whatever part of the body, by their tendency to endocarditis, are indirect causes of embolism. Destructive pulmo nary processes, pleural irrigation, and entero-peritoneal troubles may start and free thrombi that find lodgment in the brain.
Pathology.—The main feature is the softening, and this involves all tissues so far as it goes. It may be red, white, gray, yellow, or brownish, dependent on cir cumstances, duration, etc. "In the early stages of embolism or thrombosis of ves sels supplying the cortex, red or red-and white softening mixed is found in the area affected; after longer periods yellow softening is met with, or what French writers term plaques jaunes; and, after much more prolonged periods, pseudo cysts are found. owing to complete atro phy and absorption of the cerebral tissue having taken place." It is still an open question whether all focal softening of this type is due to vas cular blocking. If so, then in numerous cases either the obstructing material has disappeared or the trouble has been an arterial spasm of sufficient severity and duration to produce the same effect. The left side, and especially the left Sylvian and its branches, is the more frequent site.
Prognosis.—Experience shows that the prospect of late improvement after em bolism is as good as after cerebral hem orrhage. In favorable locations a certain amount of collateral compensation oc curs, so that a marginal zone of endan gered tissue recovers a sufficient degree of supply to resume function. Moreover, many of these are young subjects in whom some substitution of function is still possible. Immediate danger to life occurs only when the area involved is great, or where essential centres in the pons are included.
Treatment. — The treatment of this condition is in most respects the direct opposite of that for cerebral hemorrhage.
Our chief usefulness is at the time of the attack; by immediate and active meas ures, then, great good can be accom plished.
An ideal method would be the devel opment of a collateral circulation. But the brain-arteries are so largely terminal vessels as to preclude full compensation where an artery of much size is stopped.
Where the blocking is due to ather omatous or other soft material, it may break up sufficiently to pass on. We can only aid this by increasing the blood pressure and tumbling the plug along.
The most available and useful way for us is to force the embolus as far along into some peripheral vessel as possible. This is accomplished by placing the head low, giving free libations of hot and stim ulating drinks, applying bandages to the extremities or abdomen, and the admin istration of nitroglycerin or amyl-nitrite. Strophanthus may be admissible if the heart is not acting so tumultuously as to possibly tear off another plug.
The patient should be in the fully re clining position, with the head low. All depressants, depletory, and such vascular constrictors as ergot and digitalis should be most scrupulously avoided.
The management of the case after the embolic softening has fully developed is that of hemiplegics in general. We may not remove the focus, but we can look after the general health and do much, by training the patient, to regain the full power that is left.
Thrombosis.
Definition.—Under this general head ing it is convenient to include the block ing due to specific autochthonic coagu lation arterial disease, obliterating en darteritis, etc. To some extent these are distinguishable conditions clinically and therapeutically, yet they have much in common. In this sense it includes all cases where local processes or disease conditions lead to vascular occlusion and thus to the production of symptoms, if any are present. While there may be a wide difference in the origin of these cases, the final stroke usually depends on a local coagulation or deposit of material from the blood. If the vessel be pre viously narrowed, then, of course, much less will suffice to block it.