What it is

A cerebral aneurysm is an abnormal bulging in the wall of an artery in the brain. It forms when blood flow puts pressure on a weakened area of the artery wall, creating a rounded or irregular bulge that gradually enlarges.

Aneurysms can rupture, causing bleeding into the meninges (the membranes that cover the brain), a condition known as subarachnoid hemorrhage. This is a subtype of stroke and accounts for approximately 5% of all stroke cases.

Types

Saccular, fusiform, and ruptured aneurysms.

Causes

Aneurysms can occur when individuals have weak spots in the walls of their arteries that gradually dilate over the years, or as a result of physical trauma to the head.

Risk factors for subarachnoid hemorrhage include smoking, high blood pressure, excessive alcohol consumption, and conditions such as Marfan syndrome, in which the arteries have structural irregularities and may be weakened.

Main Symptoms

Most patients with brain aneurysms have no symptoms. Some people may have an aneurysm for many years without knowing it.

However, when the aneurysm significantly enlarges, it can compress structures within the skull. This compression may cause headaches, eye pain, and blurred vision. Seeking immediate medical attention when these symptoms appear can be vital to prevent aneurysm rupture and preserve brain function.

When a rupture occurs, it leads to a subarachnoid hemorrhage. Blood spreads through the meninges (the membranes covering the brain) and causes symptoms such as sudden and intense headache, nausea and vomiting, mental confusion, neurological deficits, changes in heart rate and breathing, and may lead to loss of consciousness or even death.

Diagnosis

In most cases, the patient discovers the aneurysm during an exam for investigating a neurological complaint or during routine check-ups.

Imaging tests such as magnetic resonance angiography, brain CT angiography, or cerebral angiography can identify the aneurysm’s location and size. If subarachnoid hemorrhage is suspected and imaging tests do not show significant changes, a spinal tap (lumbar puncture) may be performed to analyze the cerebrospinal fluid — the fluid surrounding the brain and spinal cord — to check for bleeding.

Treatment

Not all aneurysms require treatment. When a brain aneurysm is detected, a careful review of the patient’s medical history must be conducted to determine the need for intervention.

If the choice for intervention is made, it can be done through microsurgery, where the skull is opened and a metal clip is placed at the base of the aneurysm, or through an endovascular method, where a tiny catheter is guided through the arteries from the groin to the brain and positioned inside the aneurysm. Through this catheter, platinum microcoils are implanted to fill the aneurysm. In both cases, the goal is to block blood flow into the aneurysm.

In patients who have suffered a subarachnoid hemorrhage, aneurysms must always be treated, and the outcomes and recovery vary depending on the severity.

Prevention

In addition to avoiding smoking, people with a family history of aneurysms should have regular medical check-ups, control their blood pressure, and avoid excessive alcohol consumption.

Incidence

Non-traumatic subarachnoid hemorrhage (SAH) related to ruptured brain aneurysms has a highly variable incidence worldwide, ranging from 2 cases per 100,000 people in China to 22.5 cases per 100,000 in Finland.

Non-traumatic subarachnoid hemorrhage (SAH) related to ruptured brain aneurysms has a highly variable incidence worldwide, ranging from 2 cases per 100,000 people in China to 22.5 cases per 100,000 in Finland.

Since a portion of SAH-related deaths — approximately 12 to 15% — occur before hospital admission, the true incidence is likely higher.

Aneurysm rupture is reported at a rate of 5 to 8 cases per 100,000 people annually in the U.S., with a peak incidence around the fifth decade of life. In Brazil, incidence rates are comparable to those in the U.S., although fewer population-based studies support these statistics. Subarachnoid hemorrhage is clearly more common in women than in men, and Black and Hispanic individuals are more affected than Caucasians. Unruptured aneurysms appear to affect 2–5% of the general population.

Despite a decline in mortality in industrialized countries in recent decades, the disease still has a high fatality rate. Average mortality rates are estimated at 32% in the U.S., compared to 43% in Europe and 27% in Japan.

Despite a decline in mortality in industrialized countries in recent decades, the disease still has a high fatality rate. Average mortality rates are estimated at 32% in the U.S., compared to 43% in Europe and 27% in Japan.

By Einstein Editorial Board