Does aneurysm cause fever? Understanding the connection

September 23, 2025 •

3 min read

While an unruptured aneurysm rarely causes a fever, a rupture can trigger a systemic inflammatory response, leading to a spike in body temperature. This can happen with both cerebral and aortic aneurysms, making fever a potential red flag in specific circumstances. Understanding the complex link between a weakened vessel and fever is crucial for diagnosis and treatment.

Quick Summary

Fever is not a typical sign of a stable aneurysm, but it can occur following complications like a rupture, infection, or inflammation. Conditions such as a subarachnoid hemorrhage or an infected aortic graft can trigger a fever, indicating a severe, urgent medical event.

Key Points

Rupture Complication: Fever is not a typical symptom of an unruptured aneurysm but is common after a rupture, especially a brain aneurysm (subarachnoid hemorrhage).
Central Fever Cause: Following a brain hemorrhage, fever can be 'central' (non-infectious), caused by irritation to the brain's temperature-regulating center, the hypothalamus.
Inflammatory Response: Aneurysm ruptures and certain types of inflammatory aortic aneurysms trigger a systemic inflammatory response, leading to a fever.
Post-Surgical Risk: Patients who undergo aneurysm repair surgery, particularly craniotomy or aortic graft procedures, face a risk of post-operative infection, which can cause a fever.
Urgent Medical Attention: The presence of fever alongside other aneurysm symptoms, such as severe headache, sudden pain, or neurological deficits, should prompt immediate medical evaluation as it may indicate a serious complication.

Unruptured Aneurysms and the Absence of Fever

An unruptured aneurysm, particularly a small one, is often asymptomatic and does not cause a fever. This is because the bulge in the blood vessel wall does not actively cause an infection or a widespread inflammatory response. Symptoms, if any, are typically related to the aneurysm's size and location, such as a large brain aneurysm pressing on nerves and causing vision problems or pain. Therefore, if you have an unruptured aneurysm and develop a fever, it is more likely due to a separate, common infection like a cold or flu.

Fever After a Ruptured Brain Aneurysm

When a brain aneurysm ruptures, it causes a type of hemorrhagic stroke called a subarachnoid hemorrhage (SAH). A fever is a very common complication following SAH and is associated with poorer outcomes. The fever can be a result of several mechanisms, and it is a critical sign for medical professionals to monitor.

Non-Infectious (Central) Fever

Hypothalamic disruption: The hypothalamus, located in the brain, is the body's primary temperature regulator. Blood from a ruptured aneurysm can irritate or damage the hypothalamus, causing a "central fever" that is not caused by an infection.
Systemic inflammation: The presence of blood in the subarachnoid space triggers a widespread inflammatory response throughout the body. This systemic inflammation can lead to a fever as part of the body's reaction to the trauma.

Infectious Fever

Post-surgical infection: Patients undergoing surgery for a brain aneurysm, such as clipping or coiling, are at risk for postoperative infections, like meningitis, which can cause a fever.

Fever Associated with Aortic Aneurysms

Fever is a more common symptom in aortic aneurysms when complications arise, especially in rare cases of infection or inflammation.

Inflammatory Aortic Aneurysm

A small percentage of aortic aneurysms are categorized as inflammatory. These can trigger a systemic inflammatory response that causes fever, weight loss, and general malaise. The inflammatory process can affect nearby organs, further complicating the clinical picture.

Infected Aortic Graft

Following surgical repair of an aortic aneurysm with a graft, a rare but life-threatening complication is a graft infection. These infections can lead to a persistent fever, chills, fatigue, and other systemic signs. Given the severity, this complication requires immediate medical attention and treatment with antibiotics, and potentially further surgery.

Rupture

An impending or contained rupture of an abdominal aortic aneurysm can present with fever, often alongside severe abdominal or back pain, clammy skin, and a rapid heart rate. This is due to the inflammatory response triggered by the blood leaking into the surrounding tissues.

Differential Diagnosis: Fever After Aneurysm Events

Distinguishing between infectious and non-infectious fever in patients with aneurysm complications is challenging but critical for proper treatment. Medical teams use a range of diagnostic tools to determine the cause.


Feature	Central Fever (Non-infectious)	Infectious Fever	Inflammatory Aneurysm	Post-Graft Infection
Cause	Blood products or damage to the hypothalamus after rupture	Bacteria or other pathogens	Chronic inflammation of the aneurysm wall	Contamination during surgery or bloodstream spread
Timing	Often occurs soon after a brain aneurysm rupture	Post-operative period, can occur later	Can be a symptom before rupture in rare cases	Months or years after surgery in rare cases
Associated Symptoms	Severe headache, neurological deficits	Meningeal irritation, worsening neurological status	Weight loss, malaise, systemic issues	Chills, fatigue, pain at graft site
Diagnostic Markers	Exclusion of infection, elevated white blood cells (often non-specific)	Positive cultures (blood, CSF), specific inflammatory markers	Specific markers of inflammation, imaging	Positive cultures from infected area, specific markers

Conclusion: Interpreting the Symptom of Fever

While a fever is not an inherent symptom of an aneurysm itself, its presence can signal a serious, potentially life-threatening complication. For individuals with a known aneurysm or at risk for one, a fever should be taken seriously and investigated by a medical professional. Fever following a brain aneurysm rupture is a well-documented phenomenon linked to worse outcomes, while in aortic aneurysms, fever suggests rare but serious issues like inflammation or graft infection. Patients experiencing a fever in conjunction with other aneurysm-related symptoms, such as a severe headache, sudden pain, or neurological changes, should seek immediate emergency medical care. The specific diagnostic approach will depend on the type and location of the aneurysm and the patient's overall clinical presentation. For more information on aneurysms, symptoms, and treatment options, please consult an authoritative health resource like the National Institute of Neurological Disorders and Stroke.

Frequently Asked Questions

No, an unruptured aneurysm, especially a small one, is not typically associated with fever. The symptom is far more likely to be caused by a separate issue like an infection. A fever would only develop in the rare case of a large aneurysm pressing on the brain's thermoregulation center or if an infectious or inflammatory process is involved.

A ruptured brain aneurysm, or subarachnoid hemorrhage (SAH), can cause fever due to a systemic inflammatory response or direct irritation to the hypothalamus, the brain's temperature-regulating center, from the blood in the subarachnoid space.

Fever is not a primary symptom of a leaking cerebral aneurysm, which is often preceded by a 'sentinel headache'. However, a full rupture can quickly follow and, in that case, a fever may develop as part of the subsequent inflammatory response.

An inflammatory aortic aneurysm is a rare condition where the aneurysm sac becomes chronically inflamed. This systemic inflammatory process can cause general symptoms like fever, fatigue, and weight loss, and can affect nearby organs.

Yes, it is possible to develop a fever after aneurysm surgery. This can be caused by post-operative infections, such as meningitis after brain surgery or a graft infection after aortic repair. It may also result from a non-infectious inflammatory reaction.

It is not possible to determine this without medical evaluation. If you have risk factors for an aneurysm and experience a fever along with other concerning symptoms like a sudden, severe headache, severe abdominal or chest pain, or neurological changes, you should seek emergency medical care immediately.

Fever after an aneurysm rupture should be managed under strict medical supervision. It can be a complication that worsens outcomes, potentially affecting blood flow and oxygenation to the brain. Your medical team will decide on the appropriate treatment based on the cause and your overall condition.