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  • Updated 02.21.2024
  • Released 10.23.1995
  • Expires For CME 02.21.2027

Unruptured cerebral aneurysms



Cerebral aneurysms are common in the general population, with a prevalence of 2% to 5% (36). Many unruptured cerebral aneurysms can be safely and durably treated with microsurgical or endovascular techniques. The technical feasibility of aneurysm treatment is only one aspect of the comprehensive assessment for each patient. Part of the workup for a given patient is making a clinical decision on whether or not to treat the unruptured aneurysm. Several factors are considered, including patient age, risk factors of aneurysm rupture, family history, and aneurysm size and morphology. Aneurysm rupture has a mortality as high as 10% to 12% in the first 24 hours (36). Thus, the anxiety seen in patients diagnosed with an unruptured cerebral aneurysm can be tremendous, and this often drives the decision to treat in many cases. This article reviews the epidemiology, pathophysiology, diagnostic workup, treatment strategies, and clinical outcomes that should be considered before making management decisions regarding unruptured cerebral aneurysms.

Key points

• Saccular or “berry” aneurysms are abnormal focal outpouchings of cerebral arteries that typically occur at vessel bifurcations.

• Unruptured intracranial aneurysms have an average prevalence of 2% to 3% in the general population.

• Most cerebral aneurysms occur spontaneously, although traumatic, infectious, and malignancy-associated etiologies are also recognized.

• Hypertension and cigarette smoking are significant modifiable risk factors associated with spontaneous cerebral aneurysms.

• In general, cerebral aneurysms rupture at a rate of 1% to 2% per year, depending on morphology and location, with a mortality as high as 10% to 12% within the first 24 hours of rupture.

• Management options for unruptured intracranial aneurysms include observation or treatment with either open surgery or endovascular techniques.

• Treatment decisions for unruptured cerebral aneurysms should be made in consultation with an experienced, multidisciplinary neurovascular team.

Historical note and terminology

The modern era of unruptured cerebral aneurysm detection traces its roots to the development of cerebral angiography by Egas Moniz in the late 1920s (13). Prior to this time, unruptured cerebral aneurysms were primarily detected during autopsy or incidentally after craniotomy for various indications. Initial treatment strategies for incidentally discovered unruptured cerebral aneurysms were often indirect with uncertain efficacy. Victor Horsley was the first surgeon to apply Hunterian ligation of the internal carotid artery to treat an unruptured cerebral aneurysm in 1885 (33). Direct surgical obliteration of cerebral aneurysms would not occur until sometime later when Norman Dott successfully muscle wrapped a ruptured aneurysm in 1931 (46). Subsequently, Dott pioneered the technique of aneurysm neck suture ligation. Walter Dandy ushered in the era of cerebral aneurysm clip occlusion; in 1937, he applied a silver clip to the neck of an unruptured posterior communicating artery aneurysm. Dandy reported an uneventful recovery with improvement in the patient’s preoperative third nerve palsy (11).

Diagnostic and therapeutic techniques for managing unruptured cerebral aneurysms were further refined in the decades to come with the advent of microsurgery, improvement in catheter angiography and noninvasive imaging, and the development of endovascular occlusion methodologies. Much like initial open surgical strategies for treating cerebral aneurysms, endovascular strategies were initially indirect, often utilizing proximal artery balloon occlusion. In the early 1990s, direct endovascular occlusion techniques were developed, culminating in FDA approval of platinum Guglielmi detachable coils in 1995 (16; 17).

Flow diverting stents such as the Pipeline embolization device (Medtronic), the SILK device (Balt), the surpass flow diverter (Stryker), the FRED flow redirection endoluminal device (Microvention), and others are now being investigated or routinely used to treat select anterior circulation aneurysms (08). The success seen with using these stents for select indications has led some to pursue a variety of off-label uses to treat other complex aneurysms (32).

The latest iteration of the flow diverters include Pipeline Flex with or without Shield technology and FRED X. These devices provide easier delivery as well as a coating that reduces thrombogenicity of the stent.

The latest tools in the armamentarium of the neurointerventionalist are intrasaccular devices that can be placed inside the aneurysm. Two such devices, the Woven EndoBridge (WEB) device (Microvention) and the Pulserider (Cerenovus) aneurysm neck reconstruction device, are the latest devices especially useful for wide neck aneurysms that would be challenging for coils and stents (39; 03).

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