Recurrent unconsciousness due to bilateral middle cerebral artery stenosis.

Unconsciousness may be caused by transient ischemia of the bilateral hemisphere or brain stem. We report a case of recurrent unconsciousness in which angiography confirmed an occluded left middle cerebral artery (MCA) with well-established collateral compensation, along with a severely stenotic right MCA with poor collateral compensation, which was consistent with decreased cerebral blood flow and cerebral blood volume seen on a computed tomography perfusion study. A stent was placed in the patient's right MCA, after which the symptom disappeared completely. This case demonstrates that bilateral MCA stenosis may lead to recurrent unconsciousness through the mechanism of hypoperfusion.