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.
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