Detection of subarachnoid hemorrhage by bilateral transcranial laser doppler fluxmetry allows long-term studies in mice.

Abstract

BACKGROUND: The murine middle cerebral artery (MCA) perforation model is widely used to study subarachnoid hemorrhage (SAH) but typically requires invasive intracranial pressure (ICP) monitoring to prove successful induction of hemorrhage. However, ICP probe placement causes substantial additional parenchymal damage, confounding long-term structural and functional assessments. Therefore, we investigated whether bilateral transcranial cerebral blood flow (CBF) monitoring, which does not cause any parenchymal damage, can reliably detect SAH induction in mice. NEW METHOD: SAH was induced in 25 male C57BL/6 mice with simultaneous ICP and bilateral CBF monitoring over the MCA territory. An additional 40 mice underwent SAH surgery using only bilateral CBF monitoring (without ICP monitoring). Ipsilateral and contralateral CBF and ICP curves were analyzed to identify reliable predictors of successful SAH induction. RESULTS: MR imaging revealed progressive parenchymal injury caused by the ICP probe. SAH was reproducibly induced without ICP monitoring when bilateral CBF dropped > 50 % from baseline within 90 s after perforation. Using this minimally invasive approach, SAH could be consistently induced by different surgeons, with severity and outcomes comparable to those with ICP monitoring. COMPARISON WITH EXISTING METHODS AND CONCLUSION: ICP probe placement introduces parenchymal damage and may therefore limit the validity of long-term outcome studies. Our findings suggest that bilateral CBF monitoring can effectively replace ICP measurement, reducing invasiveness and enabling valid long-term SAH experiments in mice.