Unruptured cerebral aneurysms

Jason A Ellis MD (

Dr. Ellis of Lenox Hill Hospital, Northwell Health, has no relevant financial relationships to disclose.

E Sander Connolly Jr MD (

Dr. Connolly of Columbia University Medical Center has no relevant financial relationships to disclose.

Philip M Meyers MD (

Dr. Meyers of Columbia University Medical Center has no relevant financial relationships to disclose.

Steven R Levine MD, editor. (

Dr. Levine of the SUNY Health Science Center at Brooklyn has no relevant financial relationships to disclose.

Originally released October 23, 1995; last updated July 9, 2018; expires July 9, 2021

This article includes discussion of unruptured cerebral aneurysms, saccular aneurysm, berry aneurysm, and brain aneurysm. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Most unruptured cerebral aneurysms can be safely and durably treated using either microsurgical or endovascular techniques. The technical feasibility of aneurysm treatment is only 1 aspect of the comprehensive assessment that each patient should undergo, however. Needless to say, making a clinical decision whether to treat a given aneurysm can be extremely difficult. 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. In this article we will review the epidemiology, pathophysiology, diagnostic workup, treatment strategies, and clinical outcomes that should be considered prior to 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 are acquired and occur spontaneously although traumatic, infectious, and malignancy-associated etiologies are also recognized.


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


• In general, cerebral aneurysms rupture at a rate of 1% to 2% per year.


• Management options for patients with 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 (Doby 1992). Prior to this time, unruptured cerebral aneurysms were primarily detected during autopsy or incidentally after craniotomy for a variety of indications. Initial treatment strategies for incidentally discovered unruptured cerebral aneurysms were often indirect with uncertain efficacy. Victor Horsley is credited with being the first surgeon to apply Hunterian ligation of the internal carotid artery for the treatment of an unruptured cerebral aneurysm in 1885 (Polevaya et al 2006). Direct surgical obliteration of cerebral aneurysms would not occur until sometime later when Norman Dott successfully muscle wrapped a ruptured aneurysm in 1931 (Todd et al 1990). Subsequently, Dott went on to pioneer the technique of aneurysm neck suture ligation. The era of cerebral aneurysm clip occlusion was ushered in by Walter Dandy, who in 1937 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 (Dandy 1938).

Diagnostic and therapeutic techniques for the management of unruptured cerebral aneurysms were further refined in the decades to come with the advent of microsurgery, improvement in catheter angiography and noninvasive imaging, and most recently, the development of endovascular occlusion methodologies. Much like initial open surgical strategies for the treatment of 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 (Guglielmi et al 1991a; Guglielmi et al 1991b).

Flow diverting stents such as the Pipeline embolization device, the SILK device, the surpass flow diverter, the flow redirection endoluminal device, and others are now being investigated or routinely used to treat select anterior circulation aneurysms (Brouillard et al 2016). The success seen with the use of these stents for select indications have led some to push the envelope in pursuing a variety of off-label uses to treat other complex aneurysms (Patel et al 2017).

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