Moyamoya disease with posterior communicating artery aneurysm: a case report.

In moyamoya disease (MMD), subsequent aneurysm in the proximal part of the posterior communicating artery (PcomA) is extremely rare. We report the case of a middle-aged female patient with MMD, who presented with a ruptured wide-necked aneurysm at the proximal part of the developed PcomA that converged with the posterior cerebral artery (PCA) and supplied the distal area. Endovascular treatment was performed, but the stent-assisted coil embolization resulted in occlusion of the internal carotid artery (ICA) above the ophthalmic artery and PcomA. Due to good compensatory collateral circulation, the patient was improved after surgery and had no complications. One-year followup DSA did not show recurrence of the aneurysm. The right ICA was still embolized, but with good compensatory collateral circulation. We conclude that, for an MMD patient with an aneurysm at the proximal part of the developed PcomA, if the ICA and PcomA are accidentally occluded, then the patient may still have a good prognosis due to sufficient collateral blood circulation.