Surgical Management of Anterior Cerebral Artery Aneurysms of the Proximal (A1) Segment

Objective

To report a series of 20 consecutive patients with aneurysms of the proximal segment (A1) of the anterior cerebral artery (ACA.

Methods

The medical records of patients who had undergone surgery for intracranial aneurysms at two institutions between January 1, 1989, and February 1, 2009, were reviewed. Mean patient age was 52.15 years (range 39–69 years). All 20 patients underwent direct surgery, with clipping or trapping, via standard pterional craniotomy.

Results

The incidence of A1 segment aneurysm was 0.59%. There were 16 women and 4 men, showing a strong predominance of this lesion in women. Mean aneurysm size was 6.95 mm (range 3–10 mm). Four patients (20%) had multiple aneurysms, and three patients (15%) had associated vascular anomalies. Among patients whose aneurysms originated from perforating arteries, dissection sacrificed the perforating arteries in two patients, and the perforating arteries occluded postoperatively in three patients. In the patients whose aneurysms did not originate from perforating arteries, no perforating arteries were sacrificed during dissection, and perforating arteries became occluded in two patients postoperatively. There was no statistically significant difference between the two groups of patients regarding the incidence of injury or occlusion. Clinical outcomes were as follows: good recovery in 15 (75%) patients, moderate disability in 2 (10%) patients, severe disability in 2 (10%) patients, and death in 1 (5%) patient.

Conclusions

The important consideration in surgery for intracranial aneurysms is preservation of the perforating arteries, through cautious dissection around the neck or dome and avoidance of direct clip compression, even after releasing the retracted frontal lobe.

Introduction

The course of the proximal segment (A1) of the anterior cerebral artery (ACA) varies greatly according to its length and dominance, sometimes looping under the frontal lobe (11). A1 segment aneurysms constitute less than 1% of all intracranial aneurysms, but they are challenging to treat because of their small size and close relationship to the perforating arteries (4, 5, 12, 15). Generally, A1 segment aneurysms are smaller than intracranial aneurysms (1, 4, 5, 12, 14, 15). These aneurysms are unique because they are usually associated with vascular anomalies and sometimes are part of multiple aneurysmal occurrences (1, 4, 5, 12, 15). A1 trunk anomalies include hypoplasia, aplasia, duplication, azygos ACA, fenestration, and, very rarely, an infraoptic course (11). A1 segment aneurysms, especially lesions originating from perforating arteries, are difficult to treat because of the risk of injury to the perforating arteries around the aneurysm and the usual location of the aneurysm in the surgical field; it is frequently behind the parent artery, which covers the aneurysm neck or dome.

These aneurysms usually arise at the origin of the perforating arteries in the A1 segment (55.6%), and the perforating arteries may adhere to the dome of the aneurysm (4). The second most common site is the A1 segment itself (21.0%), followed by the proximal portion of the A1 fenestration (15.8%) and the cortical branch origin of the A1 segment (5.3%). In some cases, the A1 segment itself becomes a fusiform-type aneurysm (2.6%) (12). In this study, we present 20 patients who were surgically treated for A1 segment aneurysms and describe clinical status, radiologic findings, treatment, and outcome.