Experimental and clinical perspective on stroke : evaluation by behavior, magnetic resonance imaging and morphology

In order to further improve the diagnostic power of the NEU technique in the use for clinical evaluation of brain lesions, like in stroke patients, a biological model system had to be implemented where the relevant aspects of the brain injury and its effects could be mimicked.

Two well controlled and reproducible rat models were chosen, one developed by Bjelke et al. which is proposed to induce a penumbra lesion or reflect the early phase in an ischernic episode like thrombo-embolic stroke. The other model is based on a photochemical technique originally proposed by Watson ct al (Watson et al., 1985) which results in a pan-necrotic lesion and therefore can be said to mimic the end stage of an infarction. Both these models are basically different from the currently used MCAO-model, which has been extensively evaluated in the neuroscience literature. It is claimed that these models are better suited for experimental stroke research by offering the opportunity for isolated study of the different stages in the development of ischemia.

The neurological impairment and functional recovery from the brain injury was assessed by daily behavioral testing using a sensori-motor performance task. In vivo analysis of the brain lesions by MRI, which is a species independent technique, was performed using T2-, PD- and ADC-mapping as well as perfusion weighted imaging, and functional MRI in comparison with classical morphological evaluation. The characteristic features of the two different lesions were documented but the most important finding was consistent changes in cortex in corresponding regions in the contralateral hemisphere. These alterations in both MR parameters and morphological changes match in anatomical location with regions being proposed to be responsible for the functional recovery in the late phase of stroke.

Based on these findings an improved diagnostic approach is proposed using a battery of MRI tools. It also open up new aspects on therapeutic neuromodulatory approaches for treatment of brain lesions in the subacute phase.

List of scientific papers

I. Bjelke B, Chen Z, Andersson C, Rudin M, Beckman N, Reese T, Abo M, Bjelke K, Sauter A (2001). "A model of transient focal brain lesion in the sensory-motor cortex of the rat correlating with neurological impairment pathological MRI and delayed neuronal death." European Journal of Physiology (Submitted)

II. Chen Z, Abo M, Andersson B, Bjelke K, Klason T, Reese T, Bjelke B (2001). "Haemodynamic stroke model resulting in a pure penumbra cerebral lesion characterized by T2 map, proton density map, ADC map and perfusion MR." (Manuscript)

III. Chen Z, Abo M, Andersson B, Bjelke K, Lai LJ, KLason T, Reese T, Hindmarsh T, Brown A, Bjelke B (2001). "Evolution of a focal pan-necrotic lesion in the brain: a morphologic and MR-imaging study." (Manuscript)

IV. Abo M, Chen Z, Lai LY, Reese T, Bjelke B (2001). "Functional recovery after brain lesion- contralateral neuromodulation: a fMRI study." Neuroreport 12(7): (Accepted)

V. Chen Z, Li TQ, Hindmarsh T, (2001). "Diffusion tensor trace mapping in normal adult brain using single-shot EPI technique: a methodological study of the aging brain." Acta Radiologica (Accepted)

VI. Li TQ, Chen Z, Ostergaard L, Hindmarsh T, Moseley ME (2000). "Quantification of cerebral blood flow by bolus tracking and artery spin tagging methods." Magnetic Resonance Imaging 18: 503-12