Mouse intracerebral hemorrhage models produce different degrees of initial and delayed damage, axonal sprouting, and recovery.

The mechanisms of delayed damage and recovery after intracerebral hemorrhage (ICH) remain poorly defined. Two rodent models of ICH are commonly used: injection of the enzyme collagenase (cICH) and injection of autologous blood (bICH). In mice, we compared the effects of these two models on initial and delayed tissue damage, motor system connections, and behavioral recovery. There is no difference in lesion size between models. Injection of autologous blood causes greater mass effect and early mortality. However, cICH produces greater edema, inflammation, and cell death. Injection of the enzyme collagenase causes greater loss of cortical connections and secondary shrinkage of the striatum. Intracerebral hemorrhage occurs within the motor system connections of the striatum. Mapping of the projections of the forelimb motor area shows a significant sprouting in motor cortex projections only in cICH. Both models of ICH produce deficits in forelimb motor control. Behavioral recovery occurs by 5 weeks in cICH and 9 weeks in bICH. In summary, cICH and bICH differ in almost every facet of initial and delayed stroke pathophysiology, with cICH producing greater initial and secondary tissue damage and greater motor system axonal sprouting than bICH. Motor recovery occurs in both models, suggesting that motor system axonal sprouting in cICH is not causally associated with recovery.