What is Cavernous Sinus Aneurysm?
Aneurysms, which are swollen areas in an artery, that occur in the internal carotid arteries near the area of the blood vessel within the cavernous sinus, have different risks and often need different treatment compared to other brain aneurysms. The cavernous sinus is a blood-filled space located near our eye sockets. The unique thing about these aneurysms is that they are normally enclosed by the cavernous sinus’s tough outer layer, outside the subarachnoid space, which is the area between two membranes that surround the brain. This means that the risk of these aneurysms causing bleeding into this space is extremely low.
Cavernous sinus aneurysms usually occur in older people and often show up with a slow-moving loss of eye muscle function. Most of the time, these aneurysms don’t cause much harm, and many patients don’t need to be treated. However, in some patients, a procedure to block off the blood flow of the aneurysm from inside the blood vessel can be considered. It’s also crucial to remember that cavernous sinus aneurysms are not cancerous, and most of the time they don’t cause any symptoms. Therefore, good clinical judgment is necessary in deciding how to manage these anomalies.
What Causes Cavernous Sinus Aneurysm?
Doctors don’t know the exact cause of most cavernous sinus aneurysms, but they think they might be due to tissue wearing down over time. In rare cases, they could be caused by injury or infection. Unlike other types of brain aneurysms, cavernous sinus aneurysms are not strongly linked to hardening of the arteries (atherosclerosis), smoking, or high blood pressure.
Risk Factors and Frequency for Cavernous Sinus Aneurysm
Cavernous sinus aneurysms are more frequently seen in the elderly. They are more common in women than in men. This is also the case for aneurysms that develop in the cavernous sinus, a common place for aneurysm growth. However, as confirmed in a 2006 study by van Rooij and colleagues, these aneurysms compose a small portion (2.7% in their study) of all treated cerebral aneurysms. This is due to a difference in treatment guidelines and risk for subarachnoid hemorrhage (a type of stroke caused by bleeding in and around the brain), compared to aneurysms situated in other locations.
Signs and Symptoms of Cavernous Sinus Aneurysm
According to a study by Stiebel-Kalish and team in 2005, the most common initial symptoms of the condition they were studying include double vision, pain, asymptomatic coincidental findings, and optic neuropathy with weakened vision. It’s very important when someone is showing these symptoms to take a detailed medical history and carry out a physical examination that focuses on eye and neurological health, with special attention given to the cranial nerves.
- Double vision (65%)
- Pain (59%)
- Asymptomatic incidental finding (12%)
- Optic neuropathy with decreased vision (8%)
Testing for Cavernous Sinus Aneurysm
If doctors suspect you may have a cavernous aneurysm or a similar condition inside your brain (called intracranial aneurysms), they may use imaging tests like a CT scan or an MRI. These tests are not invasive, which means they don’t involve surgery or entering the body. They use advanced technology to create images of your brain and its blood vessels.
One type of test that is often used is an angiogram. During an angiogram, a dye is injected into the blood vessels to make them visible on an X-ray. A CT angiogram uses a CT scanner to obtain the images, while an MRI angiogram uses an MRI scanner. Both of these tests can be really helpful in looking at the details of an aneurysm.
However, the “gold standard” (or most accurate and trusted method) for detecting aneurysms and getting a detailed look at their shape and size is still the conventional digital subtraction angiography. This is a type of X-ray technology with the ability to subtract or remove structures not being studied. This makes it easier to see the blood vessels against the background of the skull and brain.
Treatment Options for Cavernous Sinus Aneurysm
Small cavernous sinus aneurysms, which are less than 12 mm and do not cause any symptoms, don’t require immediate treatment. This type of aneurysm is generally harmless and has a very low risk of bursting or rupturing. They are usually monitored over time using CT scans or MRI imaging. However, in about 2% of cases, these asymptomatic patients may experience clotting events and sudden clot formation. When an aneurysm appears unstable or growing, or if a patient starts experiencing symptoms, then treatment becomes necessary.
Indications for treatment might include severe pain, double vision or deteriorating vision, a connection developing between the cavernous sinus and the carotid artery due to a ruptured aneurysm, the aneurysm eroding through the bone into the sphenoid sinus that can cause severe nosebleeds, and extension into the subarachnoid space.
Treatment methods have evolved over time and can be divided into destructive or reconstructive strategies. Destructive strategies include blocking off the parent vessel (the main blood supply to the aneurysm) through open surgery or an endovascular procedure. This is typically done after an angiogram with a temporary balloon blocking the vessel to see if there’s adequate blood flow from other vessels to compensate. If there’s a connection between the cavernous sinus and the carotid artery, this test should be performed with the balloon placed after the aneurysm to prevent false-positive results.
If an aneurysm in the cavernous sinus ruptures, it constitutes a surgical emergency needing the expertise of a neurosurgeon. The actual surgery done will depend on where the rupture occurred, the patient’s overall health and age, and the availability of endovascular therapy.
Reconstructive methods for treating cavernous aneurysms have come a long way from being limited to clip ligation surgery. However, this approach often led to significant side effects due to the large size of these aneurysms, their hardening due to atherosclerosis (plaques in the blood vessels), and the careful dissection of the cavernous sinus, which puts the nearby cranial nerves and parent vessel at risk. With advances in endovascular technology, it’s now possible to reduce the blood flow within an aneurysm using detachable aneurysm coils and stents, promoting blood clotting and decrease in aneurysm size. Flow-diverting stents represent the latest technological advance for managing these lesions. They work by disrupting the blood flow within the aneurysm, thus leading to gradual clotting of the aneurysm. According to long-term studies, this method has a 95% success rate over five years, with a 5.6% risk of major neurological side effects.
What else can Cavernous Sinus Aneurysm be?
These are some conditions that may present with similar symptoms:
- Actinomycosis
- Cavernous sinus thrombophlebitis
- Dural arteriovenous fistula
- Hemangioma
- Hemangiopericytoma
- Meningioma
- Rhinocerebral mucormycosis
What to expect with Cavernous Sinus Aneurysm
In general, the outlook is favorable. Most small cavernous sinus aneurysms (a blood-filled bulge in a vein behind the eye) don’t present any symptoms. They also have a very low risk of rupturing or breaking open.
If these aneurysms do become larger or cause symptoms, they can be managed with a procedure known as endovascular balloon occlusion. This is a minimally invasive procedure where a small balloon is inserted to help control blood flow. This typically yields excellent results.
The health impacts, or morbidity, of these aneurysms are generally quite low. However, if it is decided that surgery is needed to fix a cavernous sinus aneurysm, there’s always concern about potential neurological (related to the nervous system) or ophthalmological (related to the eyes) deficits, or problems.
As a result, it’s essential that a wise decision is made when considering an open procedure—a type of surgery where a larger incision is made enabling the surgeon to directly see and treat the problem.
Possible Complications When Diagnosed with Cavernous Sinus Aneurysm
An abnormal neurologic and eye exam may reveal certain conditions such as cranial nerve issues, specifically cranial nerves III, IV, and VI, Horner syndrome, a condition that may impact part of your face, optic nerve damage due to compression, altered sensation linked to cranial nerve V, and an unusual reaction from the cornea to stimulation.
In a study conducted in 2006 by Van Rooij and his team, they reviewed 41 cases of symptomatic cavernous aneurysms, which is a type of brain aneurysm. The study discovered that:
- 68% of them had visual symptoms or ophthalmoplegia, a condition causing eye muscle weakness.
- 24% experienced a cavernous carotid fistula, an abnormal connection between the carotid artery and the cavernous sinus.
- 5% had a subarachnoid hemorrhage, which is bleeding in the space surrounding the brain.
- 2% reported nosebleeds.
Preventing Cavernous Sinus Aneurysm
It’s important to explain to the patient that ongoing monitoring is needed if the aneurysm is managed with a wait-and-see approach. The patient should also be aware of the potential problems that can arise if the aneurysm ruptures or if it is repaired surgically. An aneurysm is an abnormal bulge in a blood vessel wall, and rupture (a burst or break) can lead to internal bleeding and other serious complications. Similarly, having surgery to fix the aneurysm also has its own set of risks.
