ANEURYSMS OF INDIVIDUAL ARTERIES
#Thoracic Aneurysm.#--All varieties of aneurysm occur in the aorta, the
fusiform being the most common, although a sacculated aneurysm
frequently springs from a fusiform dilatation.
The _clinical features_ depend chiefly on the direction in which the
aneurysm enlarges, and are not always well marked even when the sac is
of considerable size. They consist in a pulsatile swelling--sometimes in
the supra-sternal notch, but usually towards the right side of the
sternum--with an increased area of dulness on percussion. With the
X-rays a dark shadow is seen corresponding to the sac. Pain is usually a
prominent symptom, and is largely referable to the pressure of the
aneurysm on the vertebrae or the sternum, causing erosion of these bones.
Pressure on the thoracic veins and on the air-passage causes cyanosis
and dyspnoea. When the oesophagus is pressed upon, the patient may have
difficulty in swallowing. The left recurrent nerve may be stretched or
pressed upon as it hooks round the arch of the aorta, and hoarseness of
the voice and a characteristic "brassy" cough may result from paralysis
of the muscles of the larynx which it supplies. The vagus, the phrenic,
and the spinal nerves may also be pressed upon. When the aneurysm is on
the transverse part of the arch, the trachea is pulled down with each
beat of the heart--a clinical phenomena known as the "tracheal tug."
Aneurysm of the descending aorta may, after eroding the bodies of the
vertebrae (Fig. 71) and posterior portions of the ribs, form a swelling
in the back to the left of the spine.
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