While complete neck clipping of ruptured cerebral aneurysms prevents rerupture, recurrent subarachnoid hemorrhage (SAH) due to the rupture of an aneurysm at the same sites of the previous aneurysm may occur, even if no residual neck was detected during and after neck clipping. We present the cases of 3 patients with recurrent SAH due to regrowth after neck clipping of aneurysms at the anterior communicating artery (AComA). Two of the recurrent AComA aneurysms, accessed via the pterional

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... , arose from the arterial wall adjacent to the previous necks; the third was a de novo aneurysm. Because their growth was in a posterior or superior direction, we posit that a portion of the neck was inadvertently not clipped during the first operation, and thus, flow in the AComA and perforators to the hypothalamus was maintained. Our findings suggest that unrecognized residual necks, vascular wall fragility around the earlier aneurysm, and hemodynamic changes following neck clipping contributed to their recurrence of SAH. Therefore, we recommend follow-up angiographic study to confirm complete neck clipping, especially in patients in whom the pterional approach was used.