In-Hospital Mortality in Small (<5 mm) Intracranial Aneurysms: Impact of Rupture Status, Treatment, and Complications in a Multicenter Latin American Cohort
This multicenter Latin American study of 1,519 patients reveals that in-hospital mortality for small (<5 mm) intracranial aneurysms is significantly higher in ruptured cases (18%) compared to unruptured ones (3%), with overall death rates driven primarily by rupture status, age, and treatment-related complications.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Inside the delicate network of blood vessels that nourish the brain, tiny weak spots can form on the vessel walls. These are known as intracranial aneurysms, and while they are relatively small, they carry a significant risk. When one of these weak spots bursts, it causes a subarachnoid hemorrhage, a type of stroke where blood leaks into the space surrounding the brain. This event is often devastating and can be fatal very quickly. However, many aneurysms never burst; they are found incidentally during scans for other reasons. The medical challenge lies in deciding how to manage these tiny lesions, especially those smaller than five millimeters. Doctors must weigh the risk of the aneurysm rupturing naturally against the risks of treating it, a decision that becomes even more complex when the patient is in a hospital setting where other complications can arise.
To understand how these small aneurysms affect patients in the real world, a team of researchers across Latin America conducted a large study looking at the outcomes of nearly 1,520 patients treated between 2017 and 2023. The study focused specifically on aneurysms smaller than five millimeters, a size category where treatment decisions are often debated. The researchers gathered data from eight specialized centers in five different countries, including Argentina, Colombia, Chile, Ecuador, and Uruguay. They examined every aspect of the patients' hospital stay, from their age and medical history to the specific treatment they received and any complications that occurred before they were discharged. The primary goal was to determine how many patients died during their hospitalization and to identify what factors made death more likely.
The results revealed a stark difference in outcomes depending on whether the aneurysm had already burst. Among the patients whose aneurysms had ruptured, causing a hemorrhage, the in-hospital mortality rate was 18 percent. In contrast, for those whose aneurysms had not ruptured, the mortality rate was only 3 percent. When looking at the entire group of patients, the overall death rate during hospitalization was 7 percent. The study found that the reasons for death were different for these two groups. For patients who arrived with a ruptured aneurysm, the severity of the initial bleeding and acute complications related to the disease itself were the main drivers of mortality. Those who presented with severe symptoms at the start of their illness faced a much higher risk of death compared to those with milder symptoms.
For patients with unruptured aneurysms, the situation was different. Because these patients were generally healthier when they arrived, the few deaths that occurred were primarily linked to the treatment process or medical issues that developed while they were in the hospital. The researchers identified several independent factors that increased the risk of death for all patients, regardless of whether the aneurysm had burst. These included being older than 65 years, having a history of a previous brain hemorrhage, and experiencing complications from the treatment or general medical issues during the hospital stay. Specifically, patients who suffered a complication directly related to the procedure, such as a clot or a new bleed caused by the intervention, faced a significantly higher risk of dying.
The study also looked closely at how the aneurysms were treated. The majority of patients, about 69 percent, received endovascular treatment, a minimally invasive procedure where doctors access the aneurysm through blood vessels using catheters. About 11 percent underwent microsurgery to clip the aneurysm, while 20 percent were managed without immediate intervention. In the group of patients with unruptured aneurysms who received endovascular treatment, the researchers noticed an association between the type of medication used to prevent blood clots and the outcome. Patients who received only a single blood thinner appeared to have a higher mortality rate than those who received two. However, the authors caution that this finding likely reflects the complexity of the cases rather than the medication itself, as doctors may have chosen the single drug for patients with more difficult anatomy or higher risks.
Ultimately, this research highlights that the path to survival for patients with small brain aneurysms depends heavily on whether the vessel has already broken. When the aneurysm is unruptured, the focus must be on preventing complications during treatment, as the disease itself is not the immediate threat. When the aneurysm has ruptured, the initial severity of the bleed dictates the outcome, and preventing further acute complications is critical. The study underscores the importance of careful risk assessment and the prevention of procedural errors, suggesting that in a hospital setting, the safety of the intervention is just as vital as the decision to intervene.
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