Carotid artery stenosis without symptoms: when to treat and when to monitor

University Hospitals Plymouth explains that the carotid artery in the neck provides the principal blood supply to the brain. It divides into two branches just below the angle of the jaw, one supplying the face and the other passing to the brain. Arteries tend to narrow where they divide, and the narrowing at this point may restrict blood supply, though more importantly debris stuck to the narrowed area may break off and travel to the brain or to the artery to the eye.

A local NHS referral guide describes carotid artery stenosis as a cause of TIA, stroke and temporary loss of vision in one eye (amaurosis fugax), and less often painful ocular ischaemia. Our TIA guide explains why such episodes need emergency assessment.

Plymouth describes the symptoms of debris reaching the brain: a mini-stroke affecting one side of the body, sometimes transient blindness in one eye lasting a few seconds, and sometimes jumbled or lost speech. Weakness appears on the opposite side of the body from the narrowing, whereas blindness affects the same side as the affected artery. A key feature of a TIA is full recovery within 24 hours. When TIA symptoms occur with a very tight narrowing there is a high risk of major stroke, greatest during the first 3 to 4 months, whereas when the narrowing is less severe, or there are no symptoms, the risk is much lower.

Asymptomatic means no such episode has occurred. Plymouth says narrowing can sometimes be detected with a stethoscope, through turbulence causing a squeaking or rushing noise, and the local NHS guide says asymptomatic disease may be found incidentally. The local NHS guide notes it is normally diagnosed after a stroke or TIA, and that such patients should be referred immediately.

Plymouth says ultrasound is the main method: it can show narrowing on screen and measure the speed of blood flow at the narrowing, which increases with the degree of narrowing. A carotid angiogram, an X-ray after dye injected through a catheter threaded from the groin under local anaesthetic, is another test, and some people have a CT or MRI brain scan to detect damage and rule out other causes. A scan is not a reason to panic: the question is how severe the narrowing is and whether you are well enough for a procedure.

The local NHS referral guide says for asymptomatic disease found incidentally, referral to vascular surgery is required only if stenosis is 70% or more, the person is aged 75 or younger and otherwise in good health, via a routine appointment. It stresses addressing cardiovascular risk factors, including antiplatelet and statin treatment. This is one area's guidance, and thresholds can differ elsewhere, so the vascular team will explain how they assess you.

Plymouth notes that some surgeons recommend treating a tight narrowing even without symptoms, particularly cardiac surgeons before heart bypass surgery, and says the aim of surgery is to reduce the risk of major stroke posed by a tight narrowing. For people with symptoms, the leaflet says the risk of major stroke is reduced from approximately 1 in 5 to 1 in 25, and that surgery should be done as soon as possible after TIA symptoms. Those figures relate to people who have had symptoms; for someone without symptoms the vascular team will explain how the balance of benefit and risk applies to them.

Plymouth says everyone will be recommended an aspirin-like drug such as aspirin, dipyridamole or clopidogrel, with some of these being unsuitable for people with peptic ulcer disease. The referral guide says cardiovascular risk factors should be addressed under local antiplatelet and statin guidelines. Stopping smoking, controlling blood pressure and cholesterol, and managing diabetes are the other main elements, as covered in our stroke and TIA guides.

Carotid endarterectomy is an operation to unblock the narrowed artery. The NHS says you usually go into hospital on the day and stay overnight; you may have a general anaesthetic or a local anaesthetic with the neck numb; a cut is made in the neck, the artery is opened and the fatty deposits removed, and it is closed with stitches, sometimes with a patch; it usually takes 1 to 2 hours. The referral guide notes that surgery is normally endarterectomy, with a carotid stent used rarely.

The NHS lists risks including a small risk of stroke, pain, numbness, bruising or swelling, rare severe bleeding or infection, nerve damage causing numbness or weakness in the face, and the artery narrowing again. Plymouth gives a stroke risk of between 1 and 3 in 100 during the operation, chest infections (particularly in smokers), wound infection, bleeding, nerve injuries (uncommon) and a risk of a fatal complication of about 1%; it stresses that a surgeon will only recommend treatment if the threat of stroke without an operation is thought to be much higher. If your own risk is higher because of other illnesses, the surgeon will discuss this.

Most people stay one night, may return to work in 2 to 3 weeks, and can drive when able to perform an emergency stop safely, normally 2 to 3 weeks after surgery, according to Plymouth. The NHS says to ask for an urgent GP appointment or NHS 111 for severe pain, wound pus or blood, swelling or a very high temperature after surgery.

The NHS says call 999 for weakness or numbness down one side of the body, blurred vision or loss of sight in one or both eyes, difficulty speaking or thinking of words, confusion and memory loss, dizziness or falling over, a severe headache or nausea and vomiting, and also if you have had signs of a stroke within the last 24 hours even if they have stopped. Plymouth also stresses that illnesses such as migraine, seizures, low blood sugar, faints and heart rhythm changes can resemble TIA, so specialist assessment is needed to find the cause. In someone known to have carotid narrowing, these symptoms are never to be waited out.