An aneurysm is a localized bulge or ballooning in a blood vessel caused by a weakness in its wall. When this occurs in the brain, it’s called a cerebral or intracranial aneurysm. An internal carotid artery (ICA) aneurysm specifically forms on one of the major arteries supplying blood to the brain.
Understanding Internal Carotid Artery Aneurysms
An internal carotid artery aneurysm is a weakened, bulging section of the internal carotid artery, a major blood vessel extending from the neck into the brain. This artery delivers oxygenated blood to essential brain regions, the head, face, and neck. The aneurysm forms when a portion of the arterial wall thins and expands. As it grows, its wall can become increasingly thin.
These aneurysms are classified by their shape. Saccular aneurysms, also known as berry aneurysms, are the most common type and appear as a rounded sac protruding from one side of the artery wall. Fusiform aneurysms involve a circumferential widening of the artery, causing the vessel to balloon out on all sides. While many internal carotid artery aneurysms remain small, larger ones carry a higher potential for severe complications, particularly if they rupture and lead to bleeding in the brain.
Factors Contributing to Aneurysm Formation
Internal carotid artery aneurysms can develop due to genetic predispositions and acquired risk factors that weaken arterial walls. Some individuals are born with inherent weaknesses in their blood vessel walls or with connective tissue disorders like Ehlers-Danlos or Marfan syndrome, which increase susceptibility. Abnormal connections between arteries and veins, known as arteriovenous malformations, are also linked to aneurysm formation.
Several acquired conditions and lifestyle choices also contribute to the risk. High blood pressure consistently stresses artery walls, promoting weakening. Atherosclerosis, a condition characterized by fatty plaque buildup within arteries, can compromise vessel integrity. Other factors include smoking and substance abuse, which can further damage blood vessels and increase the risk of aneurysm development.
Recognizing Potential Indications
Internal carotid artery aneurysms often remain unnoticed until they become large or rupture, but they can present with specific indications. Unruptured aneurysms, especially if growing, may exert pressure on nearby brain tissues and nerves. This pressure can cause pain above or behind one eye, or lead to numbness, weakness, or paralysis on one side of the face. Vision changes, such as double vision or a dilated pupil in one eye, can also occur. For aneurysms in the neck, a throbbing lump or symptoms like hoarseness or difficulty swallowing may be present due to compression of surrounding structures.
When an internal carotid artery aneurysm ruptures, it leads to a medical emergency. The most characteristic indication is a sudden, extremely severe headache, often described as the “worst headache of one’s life” or a “thunderclap headache.” This intense pain is frequently accompanied by nausea, vomiting, and a stiff neck. Other symptoms can include drowsiness, confusion, loss of consciousness, and visual abnormalities. Sometimes, a smaller leak, known as a sentinel bleed, can cause a sudden, severe headache days or weeks before a major rupture, serving as a warning sign.
Methods for Detection and Diagnosis
Detecting and diagnosing an internal carotid artery aneurysm involves advanced imaging techniques that provide detailed views of the brain’s blood vessels. Computed tomography (CT) scans are often among the first tests performed, especially in emergencies, to identify bleeding in the brain. Computed tomography angiography (CTA) offers a more specific view by injecting a contrast dye, allowing for clear visualization of the arteries and any aneurysms.
Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) are additional non-invasive tools. MRI provides high-resolution images of brain tissues, while MRA specifically visualizes blood vessels without radiation. For the most detailed assessment, cerebral angiography, also known as digital subtraction angiography (DSA), is a highly accurate method. This invasive procedure involves inserting a catheter into an artery, typically in the groin, and guiding it to the brain’s blood vessels to inject contrast dye, producing precise images of the aneurysm’s size, shape, and location.
Approaches to Management and Treatment
Managing an internal carotid artery aneurysm involves careful consideration of its size, location, whether it has ruptured, and the patient’s overall health. For small, unruptured aneurysms not causing symptoms, a “watchful waiting” approach may be recommended. This involves regular monitoring with imaging studies to track any changes. Lifestyle modifications, such as managing blood pressure and quitting smoking, are also advised to reduce risks.
When intervention is necessary, two primary treatment modalities are common: surgical clipping and endovascular coiling. Surgical clipping is an open brain surgery where a neurosurgeon accesses the aneurysm and places a small metal clip at its base to block blood flow into the bulging area. This prevents blood from entering the aneurysm and reduces the risk of rupture.
Endovascular coiling is a less invasive procedure performed through a catheter inserted into an artery, usually in the groin. The catheter is guided to the aneurysm, and tiny platinum coils are deployed inside the aneurysm sac. These coils fill the aneurysm, promoting blood clot formation within it and sealing it from the main artery. The choice between these treatments depends on various factors, including the aneurysm’s features and the patient’s condition, with endovascular coiling often being considered less risky in selected cases.