Carotid stenosis

Carotid stenosis is a narrowing (stenosis) in at least one of the two internal carotid arteries, which supply blood to the brain. A stenosis is often caused by a hardening of the blood vessels (arteriosclerosis), which reduces the blood flow and thus the blood supply to the brain.

If the blood supply to the brain falls below a critical level, a stroke can be triggered. About 20% of all strokes are the result of stenoses in the carotid artery, which are located outside the skull. The occurrence of stenoses is strongly age-dependent - in the adult population about 1-3% are affected, from the age of 65 almost 10%.

In most cases, carotid stenosis is the result of arteriosclerosis. This causes deposits of thrombi (blood clots), blood fats, connective tissue and calcium on the walls of arteries, which reduces the diameter and subsequently the blood flow of the affected vessel. Various factors for an increased risk of developing arteriosclerosis include hypertension (high blood pressure), smoking, lack of exercise, increased blood fat levels and increasing age.

Carotid stenosis can lead to the formation of thrombi (blood clots), which either completely block the vessel or are transported by the bloodstream to the brain, where they can cause a stroke (apoplexy) by blocking a smaller blood vessel.

As a rule, carotid stenoses do not cause any symptoms over a long period of time (asymptomatic carotid stenosis). Later, short-term circulatory disturbances of the brain may occur (transient ischemic attacks), temporarily causing a neurological deficit. These attacks are to be seen as harbingers of an irreversible stroke, but a stroke can occur directly in the case of carotid stenosis even without these attacks.

Since carotid stenosis is usually asymptomatic, it is often diagnosed at a relatively late stage.

The simplest method for detecting carotid stenosis is auscultation of the arteries with a stethoscope. Due to the narrowing of the blood vessels by stenoses, strong eddies occur in the blood stream at the affected location, which can be detected in the stethoscope as a stenosis sound. If the stenoses are located directly at the carotid bifurcation, they can be detected in this way with a very high probability. In the case of stenoses within the internal carotid artery, a clear stenosis sound can still be detected in about 50% of cases. In the next step, the degree of stenosis is determined with the aid of Doppler/duplex sonography (ultrasound examination). The degree of stenosis is an important aid in deciding whether the narrowing needs to be surgically repaired as soon as possible.

Another method of determining stenosis is angiography (imaging of the blood vessels) using computer or magnetic resonance imaging. This can also detect narrowing of the arteries within the skull.

In the treatment of carotid stenosis, the first priority is to treat the cardiovascular risk factors. These include smoking, lack of exercise, malnutrition, high blood lipids and elevated blood pressure. By improving these factors, the prognosis of the course of the disease can be massively improved even without medication or surgical intervention - the growth of stenoses is prevented or can even be reversed with strict lifestyle changes. In addition, platelet aggregation inhibitors are usually administered (drugs that inhibit the accumulation of blood platelets and thus the formation of thrombus - for example acetylsalicylic acid).

In addition to these treatment approaches, surgical interventions in the form of endarterectomy (removal of the narrowing) or carotid angioplasty (widening of the narrowing by means of a catheter) are also available as treatment options, especially for symptomatic patients (after a stroke or a transient ischaemic attack). Surgical intervention is most beneficial when the vessel is already constricted to more than 70% of its original diameter. Male patients benefit more from surgery, but the cause is not known.

Endarterectomy

During endarterectomy, the stenosed carotid artery is exposed through an approximately ten centimetre long incision, either under general or local anaesthesia. The vessel is cut completely, the narrowed area is removed and then the loose ends are sutured back together - if necessary with a plastic patch or a piece of vein.

The procedure takes about an hour in total, but the affected artery is only clamped for 15 to 30 minutes. During the operation, the brain is therefore mainly supplied via the artery on the other side of the neck. The risk of having a stroke during the operation due to detached pieces of the stenosis is up to 5%.

Carotid Angioplasty

Instead of removing the stenosis through surgery, it can also be dilated using carotid angioplasty. In this procedure, a balloon catheter is inserted into the femoral artery and advanced to the carotid artery, where the balloon is used to dilate the narrowed area. To ensure that the dilated area remains open for a longer period of time, a stent (tubular vessel support) is also inserted.

In contrast to endarterectomy, carotid angioplasty is not yet a proven routine procedure. It is used in patients in whom the vessel has narrowed again despite endarterectomy or if the stenosis cannot be operated on for anatomical reasons.

If the operation is successful, the risk of developing a stroke or a transient ischemic attack as a result of carotid stenosis is eliminated. However, during the operation there is a risk of about 5% that the operation will cause a stroke.

A distinction is made between primary and secondary prevention:

Primary prevention

Primary prevention of carotid stenosis is an attempt to prevent a stroke from occurring in the first place. This is done on the one hand by treating the risk factors (high blood pressure, smoking, elevated blood lipid levels, lack of exercise), but also by surgically removing symptom-free carotid stenoses with a degree of stenosis of more than 60%. Early surgery is particularly useful in men, patients under 65 years of age and patients with severely elevated cholesterol levels.

Secondary prevention

The aim of secondary prevention is to reduce the risk of further attacks after a stroke. If the carotid artery is more than 70% narrowed by a stenosis, this narrowing should be removed by endarterectomy. However, if it is less narrowed, the risk of stroke must be weighed against the risk of surgery, depending on the underlying conditions.