It is a notable fact that a septic cere bral embolism is far more liable than any other to form the starting-point of a hemorrhage. It appears to start from the eroded end of the vessel.
Aneurisms of the brain-arteries in children are said to owe their origin to embolic processes.
Partial Embolism.— Where the plug, owing to its angular or irregular shape, does not at first completely block the vessel. In such case either it is soon driven along to some point where it does fully occlude the lumen, or a thrombotic deposit soon forms around it and thus completes the closure.
Symmetrical Embolisms. — The corre sponding vessels on the two sides have, in rare instances, been the scat of em bolism (both medicerebrals, in Carring ton's ease, '84; both the medicerebrals and preeerebrals on each side in Eisen draht's, Med. News, '92).
Pigment and Granular Emboli.—The collections of pigment in chronic ma laria are well known. Globular hyaline masses have been described by Klebs and by Manassc, and are supposed to be de rived from the white corpuscles. So far as concerns chorea, however, clinical and experimental studies have disproved the theory that it is due to multiple small emboli.
Fat-embolism.—This affects primarily the lungs, but in general fat-embolism the brain-arteries may also be invaded. Only in severe cases are serious brain symptoms produced, and fever (Scriba, '79) does not result.
Air-embolism.--The same applies as to fat-embolism. This refers only to cases where the air enters at other points in the body.
There is also the possibility of air en tering through the brain-vessels; but this applies not to the arteries, but to the veins and sinuses. In Genzmer's case ('77) air to a fatal extent was aspirated through the opened longitudinal sinus. Frangois-Franck's experiments ('Si) ap pear to show that by way of the vertebral veins air may be taken in through the occipital dipla veins. In the Porter case (reported by the writer, "Veins of Brain," p. 71) there was some evidence that air was introduced into brain-vessels in tetanie convulsions, the wound being across the forehead. Koerner, from a case published by him in '97, concludes that in operations on the lateral sinus, where the sinus-wall shows respiratory movements, the vessel should first be closed below before venturing to open it, lest air be sucked in.
Symptoms.—These are largely drop ping out of functions (ausfall symptome) rather than strictly postive. They are, as a rule, though not invariably, those of a sudden interruption of function of the portion of the brain involved, sudden in onset and promptly complete in effect. Barely they deepen for hours after the onset. They necessarily vary in intensity and kind according to the extent and lo cation of the area supplied by the vessel. Certain immediate effects may pass off, and some of the more lasting manifesta tions may gradually ameliorate.
There are no focal premonitions (as headache, dizziness, unilateral tinglings or numbness about the body, paresis, I etc.). And previous headaches, appar ently in relation to the trouble, count against embolism. Aphasia speaks in general more for embolism than for haemorrhage, though common enough in the latter also. Development of the con dition during sleep makes the probabili ties against embolism.
A history of past rheumatism, espe cially the presence of a heart-murmur, and still more a knowledge of previous vascular plugging (in any part of the body) are strongly suggestive of embol ism. To fully warrant the diagnosis, we must establish the existence of valvular disease or endocarditis at the time of the seizure, though various pulmonary and other conditions may suffice.
The occurrence of apoplexy or hemi plegia in persons under forty years of age has been supposed to indicate embolism, though there are too many exceptions to allow much value to any such age-rule.
The occurrence of coma argues against embolism; at least, embolism limited to the pallium is not attended by this symp tom,—and this is its most common loca tion.
The focal symptoms are those of the part involved, and may include almost any loss of function seen in brain disease, though they are more often those of the left side of the brain. For the regional diagnosis (localization) these have been given in brief outline in the schedule of arteries.