Figure 1. Illustration depicting lateral (A) and superior (B) operative views of a saccular aneurysm arising from the CA at the distal edge of the origin of the PCoA (Post Comm A). The aneurysm clearly projects posterolaterally and compresses the oculomotor nerve. Another important feature to note is that the main trunk of the AChA is juxtaposed and adherent to the sac of the aneurysm. This is critical because meticulous preservation of the integrity of this vessel is of vital significance during both microdissection and clip application. A = artery; ACA = anterior cerebral artery; Ant Chor = AChA; MCA = middle cerebral artery; Perf = perforating; Sup Hyp = superior hypophysial; III = third cranial nerve. Reproduced with permission from Rhoton Jr: Aneurysms. Neurosurgery 51 Suppl 1:121-158, 2002.

Figure 2. Left and Center: Left CA AP (left) and lateral (center) digital subtraction angiograms. A multilobulated aneurysm, approximately 10 × 15 mm in diameter, can be seen arising from the CA at the origin of the PCoA. Of note, the morphological irregularity of the lesion suggests recent rupture. Right: Left vertebral AP angiogram demonstrating a right fetal PCA, an anatomical variant with surgical significance when ipsilateral to a PCA wall aneurysm, as in this case. Unlike a typical PCoA, which can often be surgically sacrificed without undue consequences, loss of a fetal PCA in this patient could result in a major territorial infarction. This angiographic finding underscores the importance of obtaining a complete four-vessel cerebral angiographic study prior to operative treatment of any PCA wall aneurysm.

Figure 3. Postoperative AP (left) and lateral (right) cerebral angiograms obtained in the same patient represented by images in Fig. 2. Complete uncoupling of the aneurysm from the intracranial circulation can be seen, as can widely patent flow through both the fetal PCA and CA.

Figure 4. Illustrations demonstrating the two principal configurations that predispose to the development of a postoperative ischemic ACA syndrome. Left: In one case, the aneurysm originates from the main AChA trunk. Right: In the other case, the AChA originates from the base of a wide-necked AChA aneurysm. Car A = CA.