Successful clinical translation of prospective cytoprotectants will likely occur only with treatments that improve functional recovery in preclinical (rodent) studies. Despite this assumption, many rely solely on histopathologic end points or the use of one or two simple behavioral tests. Presently, we used a battery of tests to gauge recovery after a unilateral intracerebral hemorrhagic stroke (ICH) targeting the striatum. In total, 60 rats (N = 15 per group) were stereotaxically infused with 0 (SHAM), 0.06 (MILD lesion), 0.12 (MODERATE lesion), or 0.18 U (SEVERE lesion) of bacterial collagenase. This created a range of injury akin to moderate (from SEVERE to MODERATE or MODERATE to MILD lesion size B30% reduction) and substantial cytoprotection (SEVERE to MILD lesion size-51% reduction). Post-ICH functional testing occurred over 30 days. Tests included the horizontal ladder and elevated beam tests, swimming, limb-use asymmetry (cylinder) test, a Neurologic Deficit Scale, an adhesive tape removal test of sensory neglect, and the staircase and single pellet tests of skilled reaching. Most tests detected significant impairments (versus SHAM), but only a few (e.g., staircase) frequently distinguished among ICH groups and none consistently differentiated among all ICH groups. However, by using a battery of tests we could behaviorally distinguish groups. Thus, preclinical testing would benefit from using a battery of behavioral tests as anything less may miss treatment effects. Such testing must be based on factors including the type of lesion, the postoperative delay and the time required to complete testing.

Abstract-The collagenase and whole blood intracerebral hemorrhage (ICH) models are widely used to identify mechanisms of injury and to evaluate treatments. Despite preclinical successes, to date, no treatment tested in phase III clinical trials has benefited ICH patients. These failures call into question the predictive value of current ICH models. By highlighting differences between these common rodent models of ICH, we sought to help investigators choose the more appropriate model for their study and to encourage the use of both whenever possible. For instance, we previously reported substantial differences in the bleeding profile, progression of cell death, and functional outcome between these models. These and other differences influence the efficacy and mechanisms of action of various treatment modalities. Thus, in this review, we also summarize neuroprotective and rehabilitation findings in each model. We conclude that differences between ICH models along with our current inability to identify the more clinically predictive model necessitate that preclinical assessments should normally be done in both. Such an approach, coupled with better assessment practices, will likely improve chances of future clinical success. Key Words: intracerebral hemorrhage Ⅲ rodent model Ⅲ neuroprotection Ⅲ rehabilitation I ntracerebral hemorrhage (ICH) is a devastating stroke with Ϸ50% mortality by 1 month, whereas most survivors remain disabled. 1,2 Animal models of ICH have significantly advanced our understanding of pathophysiology, thereby identifying numerous therapeutic targets. 3,4 Despite the use of these models, especially in rodents, and the efficacy reported in them, 4 no treatments have been proven to help ICH patients. Notably, recent clinical failures call into question whether these models accurately reflect human ICH and whether they will be useful in successfully translating treatments from the laboratory. Similar concerns have been raised for ischemic stroke.As with ischemia, no model perfectly reflects the complexity and heterogeneity of ICH in humans. Accordingly, preclinical studies should use several models to better understand pathophysiology and to predict clinical efficacy. This article briefly discusses the 2 most widely used rodent models of ICH. Although these can be compared on many facets, we focus on bleeding profile, progression of cell death, and changes in neuroplasticity, which are all of utmost importance to final outcome. Furthermore, we highlight how these model differences impact hypothermic neuroprotection and the effects of rehabilitation. Animal Models of ICHAnimal models of primary ICH have been developed using pigs, rabbits, dogs, cats, and rodents. The bleed is usually created in the striatum, but other regions have been targeted. Experiments with inert substances (eg, balloon inflation) and blood components (eg, thrombin), to evaluate their contribution to ICH outcome are widespread. However, the most commonly used models involve intraparenchymal infusion of either autologous blood...

Following stroke, the brain undergoes various stages of recovery where the central nervous system can reorganize neural circuitry (neuroplasticity) both spontaneously and with the aid of behavioral rehabilitation and non-invasive brain stimulation. Multiple neuroimaging techniques can characterize common structural and functional stroke-related deficits, and importantly, help predict recovery of function. Diffusion tensor imaging (DTI) typically reveals increased overall diffusivity throughout the brain following stroke, and is capable of indexing the extent of white matter damage. Magnetic resonance spectroscopy (MRS) provides an index of metabolic changes in surviving neural tissue after stroke, serving as a marker of brain function. The neural correlates of altered brain activity after stroke have been demonstrated by abnormal activation of sensorimotor cortices during task performance, and at rest, using functional magnetic resonance imaging (fMRI). Electroencephalography (EEG) has been used to characterize motor dysfunction in terms of increased cortical amplitude in the sensorimotor regions when performing upper limb movement, indicating abnormally increased cognitive effort and planning in individuals with stroke. Transcranial magnetic stimulation (TMS) work reveals changes in ipsilesional and contralesional cortical excitability in the sensorimotor cortices. The severity of motor deficits indexed using TMS has been linked to the magnitude of activity imbalance between the sensorimotor cortices. In this paper, we will provide a narrative review of data from studies utilizing DTI, MRS, fMRI, EEG, and brain stimulation techniques focusing on TMS and its combination with uni- and multimodal neuroimaging methods to assess recovery after stroke. Approaches that delineate the best measures with which to predict or positively alter outcomes will be highlighted.

Diffusion tensor imaging (DTI)-based tractography has been used to demonstrate functionally relevant differences in white matter pathway status after stroke. However, it is now known that the tensor model is insensitive to the complex fiber architectures found in the vast majority of voxels in the human brain. The inability to resolve intra-voxel fiber orientations may have important implications for the utility of standard DTI-based tract reconstruction methods. Intra-voxel fiber orientations can now be identified using novel, tensor-free approaches. Constrained spherical deconvolution (CSD) is one approach to characterize intra-voxel diffusion behavior. In the current study, we performed DTI- and CSD-based tract reconstruction of the corticospinal tract (CST) and corpus callosum (CC) to test the hypothesis that characterization of complex fiber orientations may improve the robustness of fiber tract reconstruction and increase the sensitivity to identify functionally relevant white matter abnormalities in individuals with chronic stroke. Diffusion weighted magnetic resonance imaging was performed in 27 chronic post-stroke participants and 12 healthy controls. Transcallosal pathways and the CST bilaterally were reconstructed using DTI- and CSD-based tractography. Mean fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial diffusivity (AD), and radial diffusivity (RD) were calculated across the tracts of interest. The total number and volume of reconstructed tracts was also determined. Diffusion measures were compared between groups (Stroke, Control) and methods (CSD, DTI). The relationship between post-stroke motor behavior and diffusion measures was evaluated. Overall, CSD methods identified more tracts than the DTI-based approach for both CC and CST pathways. Mean FA, ADC, and RD differed between DTI and CSD for CC-mediated tracts. In these tracts, we discovered a difference in FA for the CC between stroke and healthy control groups using CSD but not DTI. CSD identified ipsilesional CST pathways in 9 stroke participants who did not have tracts identified with DTI. Additionally, CSD differentiated between stroke ipsilesional and healthy control non-dominant CST for several measures (number of tracts, tract volume, FA, ADC, and RD) whereas DTI only detected group differences for number of tracts. In the stroke group, motor behavior correlated with fewer diffusion metrics derived from the DTI as compared to CSD-reconstructed ipsilesional CST and CC. CSD is superior to DTI-based tractography in detecting differences in diffusion characteristics between the nondominant healthy control and ipsilesional CST. CSD measures of microstructure tissue properties related to more motor outcomes than DTI measures did. Our results suggest the potential utility and functional relevance of characterizing complex fiber organization using tensor-free diffusion modeling approaches to investigate white matter pathways in the brain after stroke.

Iron-mediated free radical damage contributes to secondary damage after intracerebral hemorrhage (ICH). Iron is released from heme after hemoglobin breakdown and accumulates in the parenchyma over days and then persists in the brain for months (e.g., hemosiderin). This non-heme iron has been linked to cerebral edema and cell death. Deferoxamine, a ferric iron chelator, has been shown to mitigate iron-mediated damage, but results vary with less protection in the collagenase model of ICH. This study used rapid-scanning X-ray fluorescence (RS-XRF), a synchrotron-based imaging technique, to spatially map total iron and other elements (zinc, calcium and sulfur) at three survival times after collagenase-induced ICH in rats. Total iron was compared to levels of non-heme iron determined by a Ferrozine-based spectrophotometry assay in separate animals. Finally, using RS-XRF we measured iron levels in ICH rats treated with deferoxamine versus saline. The non-heme iron assay showed elevations in injured striatum at 3 days and 4 weeks post-ICH, but not at 1 day. RS-XRF also detected significantly increased iron levels at comparable times, especially notable in the peri-hematoma zone. Changes in other elements were observed in some animals, but these were inconsistent among animals. Deferoxamine diminished total parenchymal iron levels but did not attenuate neurological deficits or lesion volume at 7 days. In summary, ICH significantly increased non-heme and total iron levels. We evaluated the latter and found it to be significantly lowered by deferoxamine, but its failure to attenuate injury or functional impairment in this model raises concern about successful translation to patients.