Cavernous Sinus Aneurysm

Etiology

The exact cause of most cavernous sinus aneurysms is not known, but experts believe that it may be a combination of degenerative changes in the tissues.[4][5] Rarely, these aneurysms can be a result of trauma or infection. These aneurysms are not as strongly associated with atherosclerosis, smoking, or hypertension as other intracranial aneurysms are.[5]

Epidemiology

Cavernous sinus aneurysms are most common in the elderly population. Cerebral aneurysms are more common in women than men, and this holds true for aneurysms in the cavernous sinus, a common site for aneurysm formation. Aneurysms, as demonstrated by van Rooij et al. 2006, represent a small percentage of treated cerebral aneurysms (2.7% in their study) given the differences in indication for treatment and subarachnoid hemorrhage risk from aneurysms in other locations.[6]

Pathophysiology

If ruptured, cavernous aneurysms most commonly cause direct carotid-cavernous fistulas, though they may also cause massive epistaxis if there is erosion into the sphenoid sinus or subarachnoid hemorrhage if there is an extension through the dural ring into the subarachnoid space. However, the most common symptoms from these aneurysms are a result of a mass effect on the adjacent cranial nerves. Many cavernous carotid aneurysms present without symptoms as incidental findings or with only mild symptoms and require no treatment.

History and Physical

Stiebel-Kalish et al. 2005 reported the most common symptoms at presentation as diplopia (65%), pain (59%), asymptomatic incidental finding (12%), and optic neuropathy with decreased vision (8%).[7] A thorough history should be taken and the physical examination should focus on the ophthalmologic and neurologic findings, specifically the cranial nerve exam.

Evaluation

Evaluation of cavernous aneurysms, as well as other intracranial aneurysms, usually can be evaluated with noninvasive computed tomogram (CT) or magnetic resonance imaging (MRI) angiography.[8][9][10] Conventional digital subtraction angiography, however, remains the gold standard for aneurysm detection and anatomic characterization.

Treatment / Management

Small asymptomatic cavernous sinus aneurysms less than 12 mm do not need emergent treatment. Most small aneurysms have a benign history and a very low risk of rupture. Lesions that are observed should be followed with serial CT scans or MRI imaging. A few small series do indicate that thromboembolic events and acute thrombosis may occur in about 2% of asymptomatic patients with cavernous sinus aneurysms.[11][12][13] However, if the lesion is unstable, appears to be growing, or the patient is symptomatic, these patients need to be treated.(B3)

Proposed indications for treatment of cavernous aneurysms include disabling pain, diplopia/decline in vision, a cavernous carotid fistula as a result of aneurysm rupture, erosion of an aneurysm through the bone into the sphenoid sinus that can result in life-threatening epistaxis, and extension into the subarachnoid space. Strategies for treatment have evolved in recent decades and employ deconstructive or reconstructive strategies. Deconstructive techniques include open surgical or endovascular parent vessel occlusion. This is most safely accomplished following an angiogram with balloon test occlusion study of the affected internal carotid artery demonstrating adequate collateral circulation to compensate for the occluded vessel. If a cavernous carotid fistula is present this study should be performed with the occlusion balloon distal to the aneurysm/fistula to prevent dumping of the collateral circulation through the fistula during the test occlusion which can result in a falsely positive test. Even if the test occlusion demonstrates inadequate collaterals to support permanent occlusion of the vessel parent vessel, sacrifice is still possible if combined with a surgical bypass.

When a cavernous sinus aneurysm ruptures, this constitutes a surgical emergency and requires an experienced neurosurgeon. The type of surgery depends on the location of rupture, the patient's comorbidity and age, and the availability of endovascular therapy. The majority of ruptured lesions are managed with endovascular techniques.

In the past, reconstructive methods for the treatment of cavernous aneurysms were limited to surgical clip ligation. This often resulted in significant morbidity secondary to the often large size and atherosclerotic nature of these aneurysms as well as the necessary cavernous sinus dissection which put the adjacent cranial nerves and parent vessel at risk. With advances in endovascular technology, aneurysm embolization with vessel preservation is often possible using a combination of detachable aneurysm coils and stents. Flow-diverting stents represent the newest technological advance in the endovascular management of these lesions. The decreased porosity of these devices results in the disruption of blood flow within an aneurysm and, in most cases, gradual aneurysm thrombosis. The long-term follow-up of the PUFS trial (Pipeline Embolization Device for Uncoilable or Failed Aneurysms) showed a 95% 5-year aneurysm occlusion rate with a 5.6% risk of major stroke neurologic death morbidity, all of which occurred within the first six months of treatment for large internal carotid artery aneurysms treated with flow-diverting devices.[14]

Differential Diagnosis

• Actinomycosis
• Cavernous sinus thrombophlebitis
• Dural arteriovenous fistula
• Hemangioma
• Hemangiopericytoma
• Meningioma
• Rhinocerebral mucormycosis

Prognosis

Generally, the prognosis is good.

• Most small cavernous sinus aneurysms are small and asymptomatic. The risk of rupture is very low.
• Symptomatic or large lesions can be managed with endovascular balloon occlusion with excellent outcomes.
• The morbidity of these aneurysms is low.
• When surgery is done to repair a cavernous sinus aneurysm, the risk of neurological and ophthalmological deficits is always a concern, and hence, good judgment is required before undertaking an open procedure.

Complications

Abnormal neurologic and ophthalmologic examination findings included cranial neuropathies of cranial nerves (CN) III, IV, VI, Horner syndrome, compressive optic neuropathy, CN V dysesthesia, and abnormal corneal reflex. Also, van Rooij et al. 2006 found that, out of 41 symptomatic cavernous aneurysms, 68% presented with visual symptoms or ophthalmoplegia, 24% with a cavernous carotid fistula, 5% with subarachnoid hemorrhage, and 2% with epistaxis.[6]