Varieties.—There is, in the first place, a wide distinction between arterial and venous thrombosis.
Arterial. — This presents several sub forms: 1. One is due to conditions of the blood favoring the formation of clot (leucocytosis, increase of coagulation ferment), as in chlorosis and the puer perium; or to a thickening of the blood and slowing of its current, as in certain diseases attended by debility and exhaus tion.
2. Due to trauma, ligature (as in Marchand's case, '94, where fatal throm bosis of the Sylvian artery extended up from a ligation of the carotid), adjacent inflammations, and encroachments or compression, as by neoplasm. The trau matic cause may be either operative or accidental. According to Gerhardt, thrombosis in the branches of the Syl via') artery may occur in tubercular men ingitis and thus account for the hemi plegic symptoms in some of those cases.
Otherwise this form is so rare as to merit merely enumeration. The causes of both Form 1 and Form 2 act even more frequently to produce sinus-throm bosis.
3. That due to syphilitic arteritis. Here the progressive narrowing of the arterial lumen at length reaches such a degree as either to cut on directly the blood-current or to slow it so that coag ulation occurs.
4. The atheromatous and allied changes of the arterial wall found in the aged, acting in much the sanie way as the specific form. The arteriosclerosis of nephritis might be supposed to favor thrombosis, but the accompanying in crease in blood-pressure serves largely to prevent this; hEemorrhage is the far more frequent result. Gout and rheu matism are favoring antecedents.
Symptoms. — In general. these are gradual in onset and for a time pro gressive in character. In contrast to this is the fact that there are no prodromata in embolism and at least much less tend ency to them in hemorrhage. The age, general condition, and personal history of the patient give us all-important aids to diagnosis.
Loss of consciousness is not the rule in thrombosis, or not until the condition is so far advanced as to approach a fatal ending. There is a tendency to a slowing of the pulse. It may still vary consid erably from time to time, and may in crease, of course, if there is any compli cating sepsis. This slowing occurs, no
matter what part of the brain is espe cially involved, though, doubtless, it is more pronounced when the basilar is the seat,—and there is a possibility that in all cases where present it is due to par ticipation of that vessel.
Fever is not an accompaniment of the thrombotic process in itself, and occurs only secondary to some outside inflam mation or to septic disintegration of the thrombus itself. Barring sepsis, there is, on the contrary, an inclination to sub normal temperature, though this feature will take an irregular course. "Yawning, and especially sighing, at times in res piration are frequent and noticeable symptoms in thrombosis and its prece dent conditions, though also common in advanced cerebral The fact that compression of the ca rotids may aggravate existing symptoms and even bring on slight convulsions in persons suffering from impairment of the brain-circulation, especially thrombotic plugging of the basilar (Griesinger's syndrome), has suggested it as an ex pedient in the diagnosis of thrombosis. But as it affects disadvantageously the patient's cerebral condition, and possibly involves to an old person's carot ids, it is generally discountenanced.
Occasionally, in persons of some intel lectuality, it is quite possible to locate the trouble in the field of one or more arteries, preferably the Sylvian or its branches (for which purpose compare the schedule of arteries above given).
In the autochthonic form (due to over coagulability of the blood, retardation of the current, etc.) there may be no dis tinct forerunners. but only a progressive increase in symptoms and severity. This developmental stage may be very short if the process is limited to a single vessel, or may steadily increase to a fatal ter mination if it extends to other vessels, for the conditions which started the proc ess may continue to extend it. "Aphasic and amnesic defects of speech have been met with occasionally during or after acute specific diseases, or during the puerperal state; and in all such cases a thrombosis partial or complete of the left cerebral artery is the most common cause" (Gerhardt), though the same causes may favor embolism.