Fusiform Aneurysm · What Is It, Causes, Treatment, and More

A fusiform aneurysm is a type of aneurysm characterized by a circumferential, balloon-like dilation of a blood vessel. Aneurysms develop when a portion of the blood vessel wall weakens and begins to dilate. To be classified as an aneurysm, the dilation must exceed more than 50% of the vessel’s normal diameter.  

There are many different types of aneurysms based on their shape, including fusiform, saccular or berry aneurysms, and mycotic aneurysms. Fusiform shaped aneurysms balloon outward on all sides and tend to occur in large, high-pressure vessels such as the aorta, whereas a saccular aneurysm only bulges on one side, and typically occur at arterial bifurcations like the Circle of Willis in the brain. On the other hand, a mycotic aneurysm is mushroom-shaped and commonly occurs as a result of an infection, typically bacterial or fungal. 

Aneurysms can also be classified based on which layers of the blood vessel wall are involved. Blood vessels are made up of three separate layers: the tunica intima, tunica media, and tunica or adventitia. A true aneurysm is a dilation of all three layers of the vessel wall. In contrast, a pseudoaneurysm, also known as a false aneurysm, occurs when the inner two layers of the vessel wall are disrupted while the tunica adventitia stays intact, allowing blood to pool between the media and adventitia. Finally, a dissecting aneurysm develops when a tear in the tunica intima allows blood to enter the vessel wall, causing the layers to separate. 

The signs and symptoms of a fusiform aneurysm depend on the location of the aneurysm, size, and whether it is stable, expanding or rupturing. Many fusiform aneurysms, especially those in the aorta, remain asymptomatic for years and are discovered incidentally on imaging performed for other reasons. When symptoms do appear, they usually result from the aneurysm pressing on nearby structures or from compromised blood flow.  For example, an abdominal aortic aneurysm may cause a pulsatile abdominal mass, pain or throbbing in the abdomen or chest, and lower back pain. Similarly, a common iliac aneurysm may result in abdominal or groin pain. A healthcare provider may be able to feel a pulsating mass upon palpation or hear a blowing sound indicating abnormal blood flow (i.e., a bruit) upon auscultation of abdominal, common iliac, or femoral arteries, depending on the location of the aneurysm. 

On the other hand, a thoracic aortic aneurysm might present with vague chest or back pain, a persistent cough, hoarseness due to compression of the recurrent laryngeal nerve, or difficulty swallowing if the esophagus is compressed. If the aneurysm affects the aortic valve, it may also result in aortic insufficiency, a condition where the aortic valve doesn’t close completely allowing blood back into the heart with each heartbeat. 

More rarely, fusiform aneurysms may develop in cerebral blood vessels. Unlike saccular aneurysms, which tend to rupture and cause subarachnoid hemorrhage, fusiform cerebral aneurysms more often cause symptoms by compressing nearby structures or by reducing blood flow, potentially leading to ischemic stroke. 

The most dangerous complication of any aneurysm is rupture, which constitutes a life-threatening medical emergency due to the potential for massive internal blood loss. When an aneurysm ruptures, it causes sudden, severe pain, often described as tearing or ripping. This is quickly followed by signs of hypovolemic shock, including hypotension, tachycardia, cold and clammy skin, mental confusion or restlessness, and decreased urinary output due to reduced renal perfusion. 

A fusiform aneurysm should be attended to immediately as it can become life threatening. For aneurysms located at the abdomen, groin, or extremity, an ultrasound is often used initially to visualize and determine the size of the artery in question. If the aneurysm is large, the individual will often be referred directly for treatment. In other cases, a follow-up computer tomography angiography (i.e., CT angiography) may be used to confirm the diagnosis. Conversely, for a brain aneurysm, conventional angiography may be used to determine the size and location of the aneurysm within the brain. 

Once diagnosed, treatment of an abdominal, groin, or extremity aneurysm will depend on the severity, location, and individual symptoms. With small or asymptomatic aneurysms, conservative treatment may be utilized, which may include ultrasounds to assess for changes, blood pressure control, and management of any acquired risk factors (e.g., smoking cessation, antihypertensive treatment, or medication to lower cholesterol). Conversely, larger or symptomatic aneurysms—or those growing rapidly—typically require surgical or endovascular repair to prevent rupture. Endovascular repair is a less invasive approach in which a stent graft is placed inside the affected blood vessel via catheter to reinforce the weakened wall and exclude the aneurysm from circulation. In cases where surveillance is indicated, regular follow-up visits with a vascular surgeon and scheduled imaging are typically recommended to monitor the size of the aneurysm and progression.  

Preventative measures may also be used to detect aneurysms before they enlarge. According to the U.S. Preventive Services Task Force, a one-time screening ultrasound for abdominal aortic aneurysms may be recommended for males aged 65 to 75 years of age who have a history of smoking. Screening for thoracic aortic aneurysms may also be indicated in individuals with connective tissue disorders, a bicuspid aortic valve, or a family history of thoracic aortic aneurysm or dissection.