Exploring the impact of pre-anastomosis cerebral microcirculation on cerebral hyperperfusion syndrome in superficial temporal artery-middle cerebral artery bypass surgery of moyamoya disease.

Significance: Cerebral hyperperfusion syndrome (CHS), characterized by neurologic deficits due to postoperative high cerebral perfusion, is a serious complication of superficial temporal artery-middle cerebral artery (STA-MCA) surgery for moyamoya disease (MMD).

Aim: We aim to clarify the importance of assessing pre-anastomosis cerebral microcirculation levels by linking the onset of CHS to pre- and post-anastomosis hemodynamics.

Approach: Intraoperative laser speckle contrast imaging (LSCI) measured changes in regional cerebral blood flow (rCBF) and regional blood flow structuring (rBFS) within the cerebral cortical microcirculation of 48 adults with MMD.

Results: Following anastomosis, all MMD patients exhibited a significant increase in rCBF ( $279.60\%\pm 120.00\%$ , $p<0.001$ ). Changes in rCBF and rBFS showed a negative correlation with their respective baseline levels (rCBF, $p<0.001$ ; rBFS, $p=0.005$ ). Baseline rCBF differed significantly between CHS and non-CHS groups ( $p=0.0049$ ). The areas under the receiver operating characteristic (ROC) curve for baseline rCBF was 0.753. Hemorrhagic MMD patients showed higher baseline rCBF than ischemic patients ( $p=0.036$ ), with a marked correlation between pre- and post-anastomosis rCBF in hemorrhagic cases ( $p=0.003$ ), whereas ischemic MMD patients did not.

Conclusion: Patients with low levels of pre-anastomosis baseline CBF induce a dramatic increase in post-anastomosis and show a high risk of postoperative CHS.