[Clipping of upward projecting anterior communicating aneurysms via pterional craniotomy: approach from the side of A2 of anterior displacement].

The majority of anterior communicating artery(Acom) aneurysms can be approached via pterional craniotomy. When the fundus points superiorly, craniotomy in the side of A2 of posterior displacement may be advantageous for catching the aneurysm and both ACAs on the same plane. Sometimes, however, surgeons have to deliberately select a "contralateral" craniotomy to deal with other lesions in the same operative session. The first author has operated on 111 patients with Acom aneurysms during the last 8 years; 26 aneurysms projected superiorly, and 7 were approached via contralateral craniotomy because of the aneurysm multiplicity. We reviewed surgical problems in the 7 upward projecting aneurysms approached from the "contralateral" side. All aneurysms were successfully secured without any surgery related complication. However, in each case, aneurysm and both ACAs formed a straight line in the narrow surgical field, and it was difficult to handle the aneurysm behind the ipsilateral A2, particularly when it tightly adhered to the A2. Anticipating this prior to surgery allows the surgeon to know the possible problems in aneurysm dissection that may occur. Practically, wide separation of interhemispheric fissure with removal of the gyrus rectus, and dissection of the posterior aspect of the ipsilateral A2 facilitates the mobilization of A2 and exposure of the aneurysm neck. When the aneurysm is tightly adherent to the A2, however, isolation of the entire aneurysm risks tearing the aneurysm at its A2 junction. An aperture clip should be considered to avoid serious bleeding during dissection.