Carotid aneurysm

Local dilatation (limited dilation) of the intravascular lumen of any artery with bulging of its wall is called an aneurysm. Aneurysms of the carotid artery, which together with the vertebral arteries supplies blood to the brain, are rare.

Although any segment of this blood vessel can be affected, the internal carotid artery is most commonly affected. [1]

Epidemiology

Statistically, carotid artery aneurysms account for 0.4-4% of all peripheral artery aneurysms and are associated with trauma in almost half of the cases.

Among all arterial aneurysms, cases of extracranial (extracranial) aneurysms of the internal carotid artery do not exceed 2%, and aneurysms of the external carotid arteries -1%.

As noted by clinicians, aneurysms of the internal carotid artery account for 81% of cases, of the common carotid artery 8%, and of the carotid bifurcation 10%.

Bilateral aneurysms of the intracranial sections of the carotid arteries (i.e., intracranial) are identified in 13% of patients. [2]

Causes of the carotid aneurysms

An aneurysm formed in the walls of an arterial vessel is usually a complication of existing pathology, trauma, or congenital anomalies. Causes that can cause this lesion include:

• trauma;
• spontaneous dissection (dissection) of the artery in question;
• Carotid atherosclerosis (which occurs in 40% of patients);
• Arteritis (inflammation of the vascular wall with destructive changes in smooth muscle and elastin fibers);
• fibromuscular dysplasia, affecting the middle sheath (tunica media) of the vessel wall;
• connective tissue pathologies including systemic vasculitis, and Behçet's disease;
• collagen vascular diseases with disorder of connective tissue homeostasis, manifested as Marfan, Ehlers-Danlos, and Loeys-Dietz syndromes.

The infectious etiology of an aneurysm of the external carotid artery (arteria carotis externa), which runs along both sides of the neck, has been reported in rare cases of blood poisoning (septicemia) with infective endocarditis or as a complication of systemic infection (Streptococcus pyogenes, Staphylococcus aureus, Mycobacterium tuberculosis, HIV). [3]

Risk factors

Risk factors for carotid aneurysm formation include:

• advanced age;
• symptomatic arterial hypertension history, provoking atherosclerosis and gradual decrease in elasticity of the vascular wall;
• Connective tissue dysplasia (leading to abnormal tortuosity of the carotid arteries);
• The presence of aneurysms in the family history, as predisposition to the development of these arterial anomalies is often inherited.

Pathogenesis

Carotid arteries belong to the mixed type of vessels - muscular-elastic with a practical equal ratio of muscle and elastin fibers in its wall.

The pathogenesis of aneurysm development is caused by weakening of a part of the arterial wall. As a result, the thickness of the wall decreases and its most important properties - elasticity and elasticity - are reduced, while the vessel expands in this area.

That is, first there is a localized dilatation of the intravascular lumen due to the constant pressure of circulating blood on the weakened part of the arterial wall.

And then the middle sheath of the vessel wall (tunica media), which consists of extracellular matrix, smooth muscle and elastin fibers and type III collagen fibrils, begins to stretch and bulge. [4]

Symptoms of the carotid aneurysms

Both the first signs and the overall clinical picture depend on the localization of aneurysms and their size.

A small aneurysm of the common carotid artery (arteria carotis communis) and the extracranial (external) carotid artery may not show any symptoms. But if the bulge of the vascular stack increases, symptoms such as swelling of the soft tissues of the face, a pulsating mass palpable on the neck, dysphagia (difficulty in swallowing), stridor (wheezing), hoarseness appear.

The lesion may be at the site where the common carotid artery divides into the external and internal carotid artery, and it is a carotid bifurcation aneurysm. In terms of shape, they are usually spindle-shaped - fusiform carotid aneurysms; in many cases they are bilateral.

Infectious aneurysms of the external carotid artery manifest as an enlarging pulsating mass in the neck with pain and fever. Most often, it is the arteria carotis externa that is most often affected by a carotid aneurysm in a child.

In almost a third of cases, aneurysms of the internal carotid artery (arteria carotis interna) arise in its intracranial (intracranial) segment. Thus, sac-like bulging of the vascular wall is usually unilateral: a sac-like aneurysm of the left internal carotid artery is often localized in the middle segment of the internal carotid artery. Symptoms are manifested by headaches (in the region of the eye sockets and forehead), dizziness, tinnitus and head noise on the side of the lesion, persistent or transient disturbance of eye movements with double vision.

Aneurysm of the internal carotid artery arising in the area of the carotid-cavernous junction - in the area of the cavernous (cavernous) sinus of the dura mater, leads to loss of facial sensation, and pressure on the oculomotor nerve causes double vision and paralysis of the eye muscles.

Aneurysm of the supraclinoid section of the internal carotid artery (its ophthalmic segment) is localized above the outgrowth of the cuneiform bone of the skull, in the sulcus of which the vessel passes. Due to compression of the III cranial nerve (nervus oculomotorius), supraclinoid aneurysms - both left internal carotid artery aneurysms and right internal carotid artery aneurysms - cause visual impairment in the form of ophthalmoplegia. If the chiasma opticum, where the optic nerve fibers cross, is compressed, bilateral loss of visual fields may occur - hemianopsia. [5]

Complications and consequences

In cases of large aneurysms of the intracranial portions of the internal carotid artery - including supraclinoid aneurysms - complications and consequences can be in the form of secondary hypopituitarism (with deficiency of a number of essential hormones produced by the anterior lobe of the pituitary gland).

A carotid aneurysm may rupture with subarachnoid hemorrhage. Nasal bleeding and carotid-cavernous fistula formation are also possible in ruptured carotid-cavernous aneurysms.

When aneurysms are localized in the extracranial carotid arteries, their rupture is rarely observed, but thrombi may form in them, embolization of which is fraught with transient ischemic attacks or ischemic stroke. [6]

Diagnostics of the carotid aneurysms

According to experts, diagnosis of carotid aneurysms in many cases occurs after complications: stroke or transient ischemic attack. And many asymptomatic aneurysms are discovered accidentally.

To find out the causes of this pathology, patients take blood tests: general, for the level of cholesterol and lipoproteins (LDL and HDL), for the content of total protein, creatinine, urea nitrogen and others.

Using color duplex sonography of the vessels of the head and neck, cerebral magnetic resonance and CT-angiography instrumental diagnostics is performed.

Differential diagnosis with carotid stenosis, atherosclerosis of cerebral vessels, temporal arteritis, defect of the vascular wall in the form of a pseudoaneurysm is also necessary.

Treatment of the carotid aneurysms

Treatment of carotid aneurysm requires an individual approach, taking into account its localization, etiology and clinical picture. Its goal is to reduce symptoms and reduce the risk of complications.

Basically, the treatment of carotid aneurysms without surgery is that if a small, asymptomatic aneurysm is detected, a wait-and-see tactic with patient monitoring and ultrasound or CT monitoring of the affected artery every six months can be used - to prevent stroke and aneurysm rupture.

Medications are used to lower blood pressure (antihypertensive drugs), to lower blood cholesterol (antihyperlipidemic drugs), to prevent blood clots (antiplatelet drugs and anticoagulants). But they have no effect on the aneurysm itself.

The main treatment for symptomatic aneurysms of the extracranial carotid arteries is surgical treatment.

Surgery may be performed to remove (resect) the affected part of the artery with subsequent bypassing (creating a bypass for blood flow) with an artificial or autograft.

Now many angiosurgeons consider surgical resection of the aneurysm of the external carotid artery with its reconstruction - endovascular stenting, i.e. endovascular dilatation (angioplasty) as the gold standard for the treatment of extracranial carotid artery aneurysms. [7]

In cases of saccular aneurysms of the internal carotid artery (having a neck connecting to the vessel), surgical clamping is performed - clipping of the carotid aneurysm, after which blood flow in the vessel is restored.

Read also - Surgery for arterial aneurysms

Prevention

In order to reduce the risk of aneurysm development, doctors advise to follow the principles of healthy eating, monitor blood cholesterol levels, control blood pressure and treat arterial hypertension.

Forecast

Carotid aneurysm is associated with a high risk of neurologic and thromboembolic complications, as well as cranial nerve compression and rupture. Therefore, the overall prognosis of its outcome depends on many factors and cannot be 100% favorable.