Laser Speckle Imaging Of Cerebral Blood Flow During Hemorrhagic Stroke

Hemorrhagic stroke accounts for 15% of all stroke hospitalizations, and there is a very high mortality. In the study of its diagnosis and recovery, short-term and long-term changes of cerebral blood flow (CBF) are essential parameters. We employ laser speckle imaging technology to observe both short-term and long-term cerebral blood flow changes in mice with hemorrhagic stroke, to investigate its spatiotemporal characteristics of CBF change during the recovery.To prepare for the model of intracerebral hemorrhage (ICH), 14 male C57/BL6 mice were randomly divided into ICH and Saline groups. After been anesthetized by sodium pentobarbital, 30 ? l fresh autologous blood and saline were injected into rightside caudate nucleus of mice brain respectively by micro-injection pump. Laser speckle imaging were used to observe cerebral blood flow changes around hematoma of each group, CBF images were recorded before the surgery, within 2 hours after the surgery (every 10 minutes), day 1, day 2 and day 3 after the stroke.Through analysis of the laser speckle images of different regions in the mouse brain cortex and major vessels by temporal laser speckle image contrast analysis (tLASCA), we found blood flow velocity after intracerebral hemorrhage in mice reduced to the minimum and then gradually recovered within 2 hours, while areas near the hemorrhagic site recovered significantly slower than other regions. Regarding ICH mice, CBF of right hemisphere decreased more than the left counterpart immediately after the surgery. Within 3 days, CBF of right hemisphere declined at first, then increased, then declined and rebounded at last.Experiments demonstrated that whether injecting blood or saline, the cerebral blood flow in ipsilateral and contralateral both significantly reduced which suggested the mass effect was the dominant factor in the early stage of stroke recovery. According to the statistical analysis of data as well as vital signs in mice, we found that lesion due to autologous blood was mainly around the injection site, and hematoma phenomenon would last for a long period of time, also causing secondary injury. While in saline group, lesion extended through mouse cerebrum, causing severe brain edema on both hemisphere in the first few days, but the mice showed a clear trend of stroke recovery since the third day after the surgery. In the mean time, some mice showed obvious morphological changes of the blood vessels after hemorrhagic stroke indicated a collateral circulation. Both brain edema and hematoma caused hypoperfusion are around the hematoma, which increased intracerebral pressure and then caused blood vessels dilation compensatory phenomenon.In conclusion, we successfully used laser speckle imaging technology to achieve both short-term andlong-term monitoring of cerebral blood flow changes in mice with hemorrhagic stroke, which is important in the study of hemorrhagic stroke. Laser speckle imaging of mouse cerebral blood flow rate is reliable with high spatiotemporal resolution, which is able to accurately reflect the abnormal cerebral hemodynamic changes of areas around the hemorrhagic site, and also the vascular morphological changes. tLASCA was demonstrated to be effective in studying brain injury of hemorrhagic stroke in vivo. However, the physiological mechanisms of cerebral blood flow changes after hemorrhagic stroke are to be further explored and developed.