IDIOPATHIC ANEURISMS. —'These are subdivided into three varieties:— 1. rah/alai, or fusiform, in which the three coats of the artery are dilated simultaneously. The dilatation affecting the circumference as well as the length of the vessel, it presents the appearance of a circular enlargement rather than that of a tumor. It is usually observed in the cranial, thoracic, and abdominal cavities, and is generally smaller than the other varieties of aneurism.
2. Sacculated, in which the aneurism projects from the side of the artery or from that of a tubular aneurism. These are usually divided into true aneurisms, in which all the coats of the artery are dilated, and false aneurisms, in which but two coats of the artery remain: the internal and the outer. The former do not attain great size, while the latter may assume enormous proportions.
[The distinction made between true aneurisms, where all the coats of the artery are dilated, and false aneurisms (traumatic aneurisms), where the walls do not consist of all three arterial coats, is artificial and incorrect, according to Cohnheim. J. MCFADDEN GASTON.] A false, sacculated aneurism may be circumscribed, the sac in that case re maining whole, or diffuse, the sac having ruptured, allowing the blood to become diffused into the surrounding tissues, where it may become imprisoned by an artificial cavity formed by the neighbor ing cellular tissue.
3. Dissecting, in which an early rupt ure of an atheromatous abscess in the arterial wall has enabled the blood to dissect its way between the internal and external coats until, sooner or later, it makes an issue for itself into the inte rior of the vessel or exteriorly. In the former case it assumes the shape of a sessile growth. This form occurs espe cially in the aorta, where it may suggest the presence of a double aorta, and in the smaller cerebral arteries.
Symptoms. — The patients are some times made conscious of the formation of an aneurism by feeling something give way, or a sudden, sharp pain, or, in orbital aneurism, hearing a sound like a percussion-cap.
The subsequent symptoms vary ac cording to the stage of development at the time the ease is examined.
During the first stage—i.e., the period intervening between the onset and the time when the sac has become firm— pulsation of the tumor is clearly felt at each beat of the heart. If both hands are placed over it, the expansion of the growth will tend to separate them. When it is possible to apply pressure on the artery above the tumor, its size is diminished, while, if applied below, the contrary is the case. The reason for this is obvious: when the pressure is applied above the aneurism the flow of blood into the cavity is interfered with, while the blood-pressure is increased within the cavity when pressure is exerted be low. This method of examination, how ever, is not altogether safe.
The pulsations of the heart above the seat of the aneurism are weaker and slightly retarded. Sphygmographic trac ings are also modified from the normal type.
Auscultation will reveal a blowing or rasping bruit not only in the aneurism, but also in its artery, extending some distance beyond the sac. This bruit is not present in every ease. It is also heard in malignant vascular tumors, but it is strictly localized to the growth, being never transmitted along the artery.
The second stage begins when the aneurismal sac has become firm and resisting, on account of the deposit of laminated fibrin within it. In some eases no fibrinous deposit is formed, so that no second stage can properly be taken as a guide.
The pulsation becomes more indis tinct, or even altogether lost, on account of the thickening of the aneurismal wall and the deposit of fibrin. If the layer of fibrin is not of the same thickness everywhere, the pulsation may be more distinct at some points over the sac.
Pressure over the sac causes cessation of the pulsation, but the aneurismal tu mor will not vanish, on account of the fibrin deposited within it.