What is Carotid Artery Fibromuscular Dysplasia?
Fibromuscular dysplasia (FMD) is a rare disease that affects the carotid artery, a major blood vessel in the neck. It’s not caused by atherosclerosis (hardening of the arteries) or inflammation. Instead, FMD causes narrowing, known medically as stenosis, and/or balloon-like bulges known as aneurysms in medium-sized arteries. FMD primarily occurs in the distal extracranial internal carotid and kidneys’ arteries. While it’s most common in middle-aged women, it’s important to know that FMD can affect anyone regardless of age or gender.
What Causes Carotid Artery Fibromuscular Dysplasia?
We’re not exactly sure what causes fibromuscular dysplasia (FMD), but there are several theories out there. One suggests that FMD is an inherited disorder, given that about 11% of cases seem to run in the family. Another theory points towards hormonal effects because FMD is more common in women and hormones can particularly affect the middle tissue of the artery walls. Other theories propose that FMD could be caused by an immune system defect, abnormal development before birth, or an unusual distribution of tiny blood vessels, referred to as vaso vasorum.
Risk Factors and Frequency for Carotid Artery Fibromuscular Dysplasia
Fibromuscular dysplasia is a condition that affects roughly 0.42% to 3.4% of the general population. It is influenced by factors such as gender, age, and a history of smoking. The disease is most prevalent in middle-aged women in their fifties. In fact, up to 90% of patients with this condition are women. The carotid artery, which is often impacted on both sides, is involved in about 75% of the cases. Around two-thirds of these patients also have another arterial area affected.
- Fibromuscular dysplasia often connects with brain aneurysms (31%), fibromuscular dysplasia of the kidney arteries (up to 40%), and arterial tears or dissections (63.7%).
- There are gender differences in how the disease affects individuals as well.
- It affects women twice as often as men.
- Women are more likely to have issues with the extracranial internal carotid artery and are more prone to cervical (carotid and vertebral) dissections and aneurysms.
- Men, on the other hand, are more likely to have renal artery involvement and are more prone to renal dissections.
Signs and Symptoms of Carotid Artery Fibromuscular Dysplasia
Patients experiencing fibromuscular dysplasia may show a range of signs and symptoms. These can vary depending on which area of the arteries are affected. Symptoms can be similar to atherosclerotic diseases and include short temporary episodes of not enough blood reaching the brain, stroke, and high blood pressure. Other less specific symptoms could be dizziness, headaches, ringing in the ears, chest pain, and difficulty in breathing. During a physical check-up, one might see signs of Horner’s syndrome, which usually involves drooping of the eyelid and a smaller pupil, most likely caused by pressure on the nerves running along the carotid artery. There have also been cases where unusual sounds in the carotid arteries, upper abdomen, and sides of the body have been reported. Abnormalities in the cranial nerves and other nervous system deficits, along with unusual sounds in the carotid arteries, have been noted as well.
- Short temporary episodes of not enough blood reaching the brain
- Stroke
- High blood pressure
- Dizziness
- Headaches
- Ringing in the ears
- Chest pain
- Difficulty in breathing
- Signs of Horner’s syndrome (drooping eyelid and smaller pupil)
- Unusual sounds in the carotid arteries, upper abdomen, and sides of the body
- Abnormalities in the cranial nerves
- Other nervous system deficits
Testing for Carotid Artery Fibromuscular Dysplasia
Fibromuscular dysplasia (FMD), a condition that causes abnormal cell growth in your artery walls, can be diagnosed using various methods. These include ultrasound, traditional arteriography (an X-ray of the arteries), CT angiography (a type of X-ray that uses a dye and camera to take images of blood vessels), or Magnetic Resonance Angiography (MRA, a type of MRI that looks at blood vessels).
In an ultrasound, your doctor can spot abnormally high-speed blood flow in your arteries, which can point to FMD. It’s important to note, though, that ultrasounds might not reveal FMD if it’s more distant than the plaque (the sticky deposits that build up in your arteries), making it harder to see.
Arteriography is considered the most reliable method for identifying the characteristics of FMD. In many cases, FMD is an accidental discovery during an arteriography procedure for something else.
Distinct findings often noticed in people with FMD are focal stenosis, which appears smooth and band-like, and multifocal, which gives a “string of pearls” look on the image taken. In this context, ‘focal stenosis’ refers to a narrowed area in the artery, while ‘multifocal’ simply means that the narrowing appears in more than one place. The “pearls” or beads are abnormal areas in the artery that are larger in diameter than the normal vessel. These are changes caused by the disease that help doctors make a diagnosis of FMD.
Treatment Options for Carotid Artery Fibromuscular Dysplasia
If a patient doesn’t show any symptoms, treatment usually includes quitting smoking, taking medication to prevent blood clotting and high blood pressure, and regular checks. Steroid medication and blood-thinning therapy don’t typically help in treating the condition. It’s also useful to avoid activities that might cause sudden jerking movements, similar to getting jolted in a car crash, also known as ‘whiplash’.
Surgery is usually considered only if patients have symptoms or if the medications meant to control their high blood pressure don’t work.
There are a few surgical options available. Each one involves widening a narrowed artery, which is the root cause of the problem.
‘Open surgical dilation’ is one such method where sizes of rigid tubes (dilators) that expand progressively are used to widen the artery. However, this technique doesn’t use any medical imaging to guide the procedure, and doctors have to estimate the construction and kinks in the artery by touch.
If this artery is too far down the body or difficult to control manually, ‘open access balloon dilation’ may be chosen. This method uses a balloon to expand the artery. It allows doctors to check progress using medical imaging and helps to prevent blood clots.
The last and most favored method is ‘percutaneous transluminal angioplasty’ (PTA). This technique is an inside-the-artery procedure, which is best for cases involving less curved arteries and where the artery hasn’t widened to form a balloon-like place called an aneurysm. It’s a safer process compared to open surgery. In this method, a tube is passed over a wire guide, and a small balloon in this tube gets inflated, helping to widen the artery.
What else can Carotid Artery Fibromuscular Dysplasia be?
Fibromuscular dysplasia (FMD) can get mixed up with other heart and blood vessel diseases, including atherosclerosis and vasculitis. It’s crucial to distinguish between these conditions to ensure appropriate treatment.
- Atherosclerosis can impact the same arteries as FMD, especially the carotid and renal arteries. However, it usually affects older people and those with more health risks like diabetes and high levels of fat in the blood (hyperlipidemia). Also, atherosclerosis typically shows up near the start of arteries and doesn’t look like a “string of pearls” on imaging tests.
- Vasculitis is also a condition that FMD needs to be differentiated from as FMD can affect multiple systems, such as the kidneys and brain. But unlike vasculitis, FMD isn’t generally associated with a low red blood cell count (anemia), a low platelet count (thrombocytopenia) or other inflammation-related issues. Blood tests checking inflammation markers, like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are usually negative in FMD cases.
Possible Complications When Diagnosed with Carotid Artery Fibromuscular Dysplasia
Fibromuscular Dysplasia (FMD) can sometimes cause complications, but these only occur in about 10% of cases. One possible issue might be what’s called a carotid artery dissection, which could cause the artery to rupture. Other complications can include problems with the inside of an artery. This could cause reduced blood flow or result in a blood clot, which might break off and cause more problems elsewhere in the body.
Unfortunately, managing these complications can also become more complex if other conditions develop at the same time – like a blockage at the place where the carotid artery splits, which can make it hard to figure out what’s causing brain symptoms. Additionally, aneurysms outside of the brain in the carotid artery, as well as FMD affecting the arteries in the neck and kidneys, could also occur.
- Carotid artery dissection
- Artery rupture
- Problems inside the artery
- Reduced blood flow
- Blood clot formation and potential movement
- Blockage at the carotid split area
- Difficulty figuring out cause of brain symptoms
- External carotid artery aneurysms
- FMD in neck and kidney arteries
