We have assessed microthromboembolism in mice 2 days after SAH. We have no experience with the assessment of microthromboembolism at other time intervals.

After animal death, the brains should be directly processed. The method employed involves fixation in 4% formaldehyde for 48 h but shorter fixation time or no fixation after perfusion and use of frozen sections could be used in order to avoid the need for antigen retrieval. Regarding whether to perfuse the animal, if they were not perfused then it would be difficult to differentiate fibrinogen left in situ from blood clotting postmortem. On the other hand, perfusion could potentially flush out emboli from some blood vessels. A method to avoid this could be to not perfuse and to use other markers for thromboemboli that detect molecules or their epitopes that are present only in clot.

Stein et al. (5) identified microthromboemboli in histological sections of human brains obtained at autopsy from patients dying of SAH. Primary antibodies to antithrombin III were used, which would detect free antithrombin III as well as antithrombin III bound in protease complexes. Microthrombus formation has been assessed by intravital microscopy in a variety of conditions including after traumatic brain injury in mice (10). This method might be valuable for determining if the clots are emboli or thrombi.