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100 VII. Summary

drugs. This typical side-effect of the established suture-technique could be avoided

by using the new macrosphere model.

Furthermore, typical side-effects and sources of error of the macrosphere-technique

were investigated by comparison of the permanent suture-model, the transient

suture-model (90 minutes) and the macrosphere-model. Using magnetic resonance

angiography, the frequency of sufficient middle cerebral artery-occlusion (and

reperfusion) was evaluated. Infarct size and the incidence of hemorrhagic

complications were determined by using magnetic resonance imaging and

histopathology. Neurological deficits were quantified clinically.

The results indicate that the presence of focal neurological deficits alone do not

provide evidence for sufficient middle cerebral artery occlusion, since some animals

displayed neurological deficits while MR-angiography proved that the occlusion

technique failed to obstruct blood flow to the middle cerebral artery. Thus sufficient

vessel occlusion needs to be verified in experimental stroke models by vascular

imaging such as MR-angiography.

Subarachnoid hemorrhage represents another typical side-effect of the suture model.

This complication is caused by perforation of intracranial arteries. In the present

study, this side-effect occurred solely in animals that were subjected to the suture-

technique, but not in animals of the macrosphere-group.

Due to its uncomplicated applicability, the macrosphere technique allows middle

cerebral artery-occlusion even under difficult technical conditions, such as within the

bore of a MR-tomograph (in-bore occlusion). This technique permits investigations of

pathological changes in hyperacute phase of focal cerebral ischemia. Moreover, this

method allows a direct (“pixel-by-pixel”) comparison between pre and post ischemic

images since animals do not need to be repositioned after baseline imaging.

Basically, in-bore occlusion can be achieved by modifying the established suture-

technique. However, this procedure is technically challenging accompanied by a high

failure-rate.

In the third experiment, the applicability of the macrosphere-model for in-bore

occlusion was investigated. Minor technical modifications of the previously used

macrosphere-technique facilitated middle cerebral artery-occlusion inside the MRI-

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DCS EH-36SS Manuale Utente Pagina 112