Intracerebral Hemorrhage Following Bypass Surgery for Atherosclerotic Internal Carotid Artery Occlusion Without Hyperperfusion: The Potential Role of Donor-Recipient Mismatch.

Postoperative intracerebral hemorrhage (ICH) following superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis for atherosclerotic occlusive cerebrovascular disease is rare. Hyperperfusion syndrome is considered a primary cause; however, many aspects remain unclear. A case of a 77-year-old man referred for further examination after presenting with left-sided visual disturbance. Magnetic resonance imaging (MRI) showed no cerebral infarction, but MR angiography (MRA) revealed a left internal carotid artery (ICA) occlusion. Single-photon emission computed tomography (SPECT) using N-isopropyl-p-[I]iodoamphetamine (I-IMP) demonstrated that the cerebral blood flow (CBF) value in the left MCA territory was 77% of that on the right side, with a 9.6% increase following acetazolamide challenge. The patient underwent STA-MCA anastomosis to prevent further ischemic stroke. Post-anastomosis, the STA and M4 diameters were 3.1 mm and 1.6 mm, respectively, resulting in a caliber mismatch ratio (STA/M4) of 1.94. Postoperatively, strict systolic blood pressure control (below 130 mmHg) was implemented. However, the patient experienced partial seizures in the left face, while computed tomography (CT) revealed an ICH in the left temporal lobe on the fourth postoperative day. An increase in CBF was not considered to fall within the range of hyperperfusion on I-IMP SPECT. His symptoms gradually improved with conservative management, returning to a modified Rankin Scale of 1 by the 10th postoperative day. Even in the absence of imaging evidence of hyperperfusion, a marked donor/recipient caliber mismatch may be a potential risk factor for postoperative hemorrhagic complications following direct bypass surgery for atherosclerotic occlusive disease.