Basal Interhemispheric Approach for Clipping of Subcallosal Distal Anterior Cerebral Artery Aneurysms

Background: The evolution of endovascular devices and techniques for the treatment of intracranial aneurysms has continued to advance at an accelerating rate, precipitating a wide spectrum of predictable and unanticipated consequences. Although the overall fraction of aneurysms considered best treated by open surgery has decreased dramatically, those remaining aneurysms that are ineligible for interventional management represent a formidable and technically demanding subset of cases. Distal anterior cerebral artery aneurysms (DACAA) often fall into this category given the challenges of safe catheter placement in distal lesions, and the commonplace involvement of the other anterior communicating artery complex branches and perforators. The risk profile is further complicated in younger patients, who are potentially at higher risk for long-term recurrence after endovascular treatment, particularly if complete occlusion is not achieved. Among these, subcallosal DACAA especially carry difficult technical features in clipping as the corpus callosum intervening surgeon's working angle as a roof to the aneurysm. Correspondingly, we report a brief, illustrative case series to review the technical aspects of approaching subcallosal DACAA using the basal interhemispheric approach.

Methods: Retrospective chart review and microsurgical video analysis of 3 bifrontal interhemispheric craniotomies for clipping of subcallosal DACAA.

Results: All patients were positioned supine with the head minimally elevated and extended 15°, to allow direct visualization in parallel with the anterior fossa floor. A low midline bifrontal craniotomy was fashioned, with preservation of the inferior orbital bar and cranialization of the frontal sinuses. The dura was incised either in a V-shaped fashion meeting at the falx, followed by selective sectioning, or rectangular fashion retracted medially to the falx. With the olfactory bulbs carefully maintained and fixed in their normal anatomic position, careful subarachnoid dissection was carried posteriorly and superiorly along the interhemispheric and subfrontal planes, until distal and proximal control were established on the bilateral ACAs. In all cases, the aneurysm dome was encountered covered or buried in the corpus callosum, deep within the interhemispheric fissure and dissection of the neck proceeded once definitive vascular control had been established. Aneurysm clipping proceeded uneventfully, and the patients all recovered from surgery at their intact neurologic baseline and with complete aneurysm obliteration. Surgery was well tolerated, and no major complications were observed postoperatively or in follow-up.

Discussion: Although endovascular has become a safe and effective standard-of-care for most simple DACAA, complex lesions are prone to warrant consideration for open surgical clipping. For optimized vascular control and an ideal working axis, we recommend the low bifrontal craniotomy for subcallosal DACAA, which depends on thorough, careful dissection of the interhemispheric subcallosal cistern to maximize exposure, and to promote safe and complete clipping.

Fig 1 

Fig. 2