Cerebral hyperperfusion syndrome following combined aneurysm trapping and low-flow bypass for fusiform aneurysm of the middle cerebral artery

• Cerebral hyperperfusion syndrome (CHS) can occur following aneurysm treatment • Aneurysms may act as pressure-relieving chambers, impairing cerebral autoregulation • Many pathophysiological mechanisms may contribute to the development of CHS The mechanism of cerebral hyperperfusion syndrome (CHS) following aneurysm surgery remains unclear. We report the case of a 66-year-old woman with an unruptured large fusiform-shaped aneurysm of the left middle cerebral artery. She underwent a combination of aneurysm trapping and superficial temporal artery to middle cerebral artery anastomosis. Postoperatively, she developed motor aphasia. Computed tomography perfusion imaging and single photon emission computed tomography showed increased cerebral blood flow in the left frontal lobe. A diagnosis of CHS was made following aneurysm trapping with low-flow bypass. This case highlights the importance of assessing the risk of CHS when performing this surgical procedure.