Intracranial aneurysm of the anterior circulation.

Internal carotid artery aneurysm

Anterior cerebral artery aneurysm

Anterior communicating artery aneurysm

Middle cerebral artery aneurysm

Approximately 90% of intracranial aneurysm arise from the anterior circulation.

Anterior cerebral artery aneurysm (ACA) / Anterior communicating artery aneurysm (ACoA complex): ~30-40%

Supraclinioid internal carotid artery aneurysm ICA and ICA / posterior communicating artery aneurysm (PCoA junction): ~30%

Middle cerebral artery aneurysm (MCA) (M1/M2 junction) bi/trifurcation: ~ 20-30%

Aneurysms of the anterior circulation larger than 2cm have a complex relationship to the anterior skull base, requiring a multi-modality management approach.

In a retrospective study of 54 patients with such aneurysms who underwent clipping between 2001 and 2012 analyzes clinical and surgical data, aneurysm characteristics and correlates them with respect to the Glasgow outcome score at follow-up and immediate post-operative clinical status.

Patients with an outcome score of 5 or 4 were categorized as “good”, while those with score 3-1 were “poor”. Fisher's exact test and paired T-test (p<0.5) were used to test statistical significance for discrete and continuous variables respectively.

44 (81.4%) patients had a good outcome. Patients with non-ophthalmic/paraclinoid aneurysms had significantly lower incidence of adverse intra-operative events (p=0.035). Patients older than 50 years (p=0.045), with adverse intra-operative events (p=0.015) and post-operative infarction (p<0.001) had a poor outcome compared to those younger than 50 years age and those without adverse intra-operative events or infarctions. The grouped age variable had maximum influence on patient outcome. Location and size of aneurysm did not have an overall impact on surgical outcome. There were 4 mortalities.

Primary clipping of proximal non-cavernous aneurysms on the internal carotid artery is associated with adverse intra-operative events. A multi-modality treatment approach in these aneurysms should be individualized, more so in patients older than 50 years ¹⁾.

Patients with bilateral anterior circulation aneurysms present a management challenge. These lesions may be treated in a staged manner or alternatively, for select patients, a contralateral approach may be utilized to treat bilateral aneurysms with a single surgery.

Conventional surgical or endovascular techniques.

see Endoscope assisted surgery for anterior circulation aneurysm

Pipeline embolization device (PED) can be utilized in the treatment of distal anterior circulation aneurysms with difficult anatomy for conventional surgical or endovascular techniques. Larger-scale studies with long-term follow-up are needed to further elucidate the durability of PED treatment and its effect on perforator-rich vascular segments ²⁾.

Chohan et al. performed a retrospective analysis of all patients >18 years of age with aneurysmal subarachnoid hemorrhage (SAH) from anterior circulation aneurysms between 2008 and 2013 at the University of New Mexico Hospital. Vasospasm was characterized on days 3 through 14 after SAH based on: (1) angiography, (2) vasospasm requiring angiographic intervention, (3) development of delayed ischemic neurologic deficit (DIND), and (4) radiological appearance of new strokes.

Of 159 patients, 114 (71.6%) had “aggressive” and 45 (28.3%) had standard microsurgery. More than 60% of patients presented with a Hunt and Hess score of ≥3 and a Fisher grade (FG) of 4. Compared with standard surgery, there was a statistically significant decrease in the incidence of DIND in patients undergoing aggressive surgery (18.4% vs 37.8%, p=0.01). Moreover, there was a reduction in the number of new strokes by 30% in the aggressive surgery group with moderate or higher degrees of vasospasm (46.0% vs 76.5%, p=0.06). In the same group with FG 4 SAH, however, this difference was more than 50% (30% vs 64.7%, p=0.02).

They conclude that aggressive surgical manipulation during aneurysm surgery results in lower incidence of DIND and new strokes. This effect is most pronounced in patients with FG 4 SAH ³⁾.

Zhang et al. retrospectively assessed the records of 103 patients with ruptured, Hunt and Hess grade IV or V, anterior circulation cerebral aneurysms. The patients were divided into 2 groups (conservative group and surgical group). In surgical group, patients were divided into 2 subgroups according to surgical time (within 24 hours and at 24-48 hours). Clinical outcome was assessed at the 6-month follow-up and categorized according to modified Rankin Scale (mRS) score.Twenty percent of patients (9/44) in conservative group obtained good outcome, while 54% (32/54) in surgical group (P < 0.05). Mortality was 73% in conservative group and 40% in surgical group, respectively. In surgical group, age, Hunt and Hess grade (IV or V), and timing of intervention (<24 hours or later) influenced the clinical outcome of the patients (P < 0.05), while sex, Fisher grade, hydrocephalus, the location of aneurysms, and cerebral vasospasm (CVS) not (P > 0.05). Furthermore, 65% of patients (22/34) operated within 24 hours after onset of hemorrhage had a good outcome compared with 20% of patients (5/25) operated at 24 to 48 hours in surgical group (P < 0.05).The results indicate that keyhole approach combined with external ventricular drainage is a safe and reliable treatment for ruptured, poor-grade, anterior circulation cerebral aneurysms in early stage, which will reduce mortality ⁴⁾.

22 elective aneurysm clippings on patients ≤55 years of age were performed by the same dual fellowship-trained cerebrovascular/endovascular neurosurgeon. One patient (4.5%) experienced transient post-operative complications. 18 of 22 patients returned for follow-up imaging and there were no recurrences through an average duration of 22 months. A search in the NIS database from 2008 to 2010, also for patients aged ≤55 years of age, yielded 1,341 hospitalizations for surgical clip ligation of unruptured cerebral aneurysms. Inpatient length of stay and hospital charges at our institution using the minimally invasive thumb-sized pterional technique were nearly half that of NIS (length of stay: 3.2 vs 5.7 days; hospital charges: $52,779 vs. $101,882). The minimally invasive thumb-sized pterional craniotomy allows good exposure of unruptured small and medium-sized supraclinoid anterior circulation aneurysms. Cerebrospinal fluid drainage from key subarachnoid cisterns and constant bimanual microsurgical techniques avoid the need for retractors which can cause contusions, localized venous infarctions, and post-operative cerebral edema at the retractor sites. Utilizing this set of techniques has afforded our patients with a shorter hospital stay at a lower cost compared to the national average ⁵⁾.

Fourteen patients with anterior circulation aneurysms underwent clipping via the endoscopic keyhole approach (supraorbital approach and minipterional craniotomy). Seven patients had anterior communicating (ACom) artery aneurysms, four had middle cerebral artery (MCA) bifurcation aneurysms, two had internal carotid artery bifurcation aneurysms, and one had a posterior communicating artery aneurysm. Ten patients presented with subarachnoid hemorrhage (Hunt and Hess grade I in 6 and grade II in 4 patients), whereas the remaining four were incidentally detected. The pre-clipping dissection as well as the clipping were successfully performed endoscopically in all patients. The post-clipping inspection revealed inclusion of a perforator within the clip blades in 2 patients (ACom and MCA bifurcation) that required clip readjustment. There was no residual neck/incompletely clipped aneurysm detected on post-clipping inspection. There was no morbidity directly attributable to the use of keyhole approach or the endoscope.

Endoscopic keyhole approach for intracranial aneurysms combines the advantages of both keyhole approach and endoscopy. Endoscopic visualization can help to reduce chances of an incompletely clipped aneurysms/residual neck and the risk of parent vessel/perforator occlusion. However, the use of an endoscope in narrow corridors with space constraints has a learning curve that can be overcome by practicing on cadavers and initially performing several simple endoscopic procedures ⁶⁾.

A 57-year-old woman with incidentally discovered bilateral aneurysms (left middle cerebral artery [MCA], left anterior choroidal artery and right MCA). A contralateral approach through a left pterional craniotomy was performed for microsurgical clipping of all three aneurysms. The techniques of pterional craniotomy, contralateral approach, microsurgical clipping and intraoperative angiography are reviewed. The authors are grateful to Wuyang Yang, M.D. for his assistance. The video can be found here: http://youtu.be/MlPIu3hQZkg ⁷⁾.