The clinical features vary with the site of the aneurysm and with its rapidity and direction of growth.  A smooth, rounded swelling, which exhibits expansile pulsation, forms, usually towards the left of the middle line.  It may extend upwards under cover of the ribs, downwards towards the pelvis, or backward towards the loin.  On palpation a systolic thrill may be detected, but the presence of a murmur is neither constant nor characteristic.  Pain is usually present; it may be neuralgic in character, or may simulate renal colic.  When the aneurysm presses on the vertebrae and erodes them, the symptoms simulate those of spinal caries, particularly if, as sometimes happens, symptoms of compression paraplegia ensue.  In its growth the swelling may press upon and displace the adjacent viscera, and so interfere with their functions.

The diagnosis has to be made from solid or cystic tumours overlying the artery; from a “pulsating aorta”; and from spinal caries; much help is obtained by the use of the X-rays.

The condition usually proves fatal, either by the aneurysm bursting into the peritoneal cavity, or by slow leakage into the retro-peritoneal tissue.

The Moore-Corradi method has been successfully employed, access to the sac having been obtained by opening the abdomen.  Ligation of the aorta has so far been unsuccessful, but in one case operated upon by Keen the patient survived forty-eight days.

#Innominate aneurysm# may be of the fusiform or of the sacculated variety, and is frequently associated with pouching of the aorta.  It usually grows upwards and laterally, projecting above the sternum and right clavicle, which may be eroded or displaced (Fig. 75).  Symptoms of pressure on the structures in the neck, similar to those produced by aortic aneurysm, occur.  The pulses in the right upper extremity and in the right carotid and its branches are diminished and delayed.  Pressure on the right brachial plexus causes shooting pain down the arm and muscular paresis on that side.  Vaso-motor disturbances and contraction of the pupil on the right side may result from pressure on the sympathetic.  Death may take place from rupture, or from pressure on the air-passage.

[Illustration:  FIG. 75.—­Innominate Aneurysm in a woman, aet. 47, eight months after treatment by Moore-Corradi method (cf.  Fig. 73).]

The available methods of treatment are ligation of the right common carotid and third part of the right subclavian (Wardrop’s operation), of which a number of successful cases have been recorded.  Those most suitable for ligation are cases in which the aneurysm is circumscribed and globular (Sheen).  If ligation is found to be impracticable, the Moore-Corradi method or Macewen’s needling may be tried.

#Carotid Aneurysms.#—­Aneurysm of the common carotid is more frequent on the right than on the left side, and is usually situated either at the root of the neck or near the bifurcation.  It is the aneurysm most frequently met with in women.  From its position the swelling is liable to press on the vagus, recurrent and sympathetic nerves, on the air-passage, and on the oesophagus, giving rise to symptoms referable to such pressure.  There may be cerebral symptoms from interference with the blood supply of the brain.