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V./3.1.: Stroke
V./3.1.1.: Introduction
Important to note in radiologic aspects that the ischemic infarcts might be classified pathologically as
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- microangiopathic,
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- hemodinamic and
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- thromboembolic.
Due to the fact that radiologic appearances of these infarcts are different, we must mention it in the report, because these data provide important information for the clinician partners.
V./3.1.2.: Microangiopathic ischemic infarcts
These are the lacunar infarcts, which develop in the basal nuclei, thalamus, internal capsule and pons upon complete or partial occlusion of arterioles. Important to note in differential diagnostic respect, that lacunar infarcts cannot be easily differentiated from the dilation of Virchow-Robin-spaces by CT, whilst MR demonstrates free fluid-sign (high T2 signal) in the paravascular dilations unequivocally.
V./3.1.3. Ischemic infarcts developing on hemodynamic background
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Ischemic infarcts might occur due to reduction in perfusion at the terminal outflow of arteries as well as in marginal zones. Marginal zone infarcts can develop in the following locations:
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- in outer border-zones for ex. at the „watershed” zones of middle/anterior cerebral arteries, posterior/middle cerebral arteries, moreover
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- in internal border-zones, for ex. between the branches of middle cerebral artery (A2 part and circumferent peripheral, parenchyma supplying perforant branches). In case of global hypoxia, for ex. in case of carbon monoxide piling related toxication, effects the basal nuclei first. This is surely not visible on CT, but the detection of T2-hypointense basal nuclei on MR is obvious, as well as the consequent cortical (laminar) damages: the cortex-medulla margin wears off in CT images, hyperintensity is present on MR images. Cortical petechial bleedings can also develop later. Signs of diffuse brain edema are prominent using both imaging modalities.
V./3.1.4.: Territorial ischemic infarcts developing on thromboembolic background
V./3.1.4.1.: Importance of territorial areas in the development of thromboembolic infarcts
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„Territorial” term means that ischemia effects one-one arterial supplying areas. On the supply territory of middle cerebral artery, anterior and posterior territorial subcortical media-partial infarcts might arise according to their three branches, which can spread into the basal nuclei as well. The complete media-territorial infarct (malignant media infarct) includes the supply territory of all the three branches completely. Infarcts of anterior cerebral artery origin spread in retrograde direction parasagittaly, based on the supply territory of the artery (pericallosal artery). Localisation/shape adequete of the evolved emollition is very characteristic of the posterior cerebral artery-territorial infarcts and the territorial infarct caused by the occlusion of cerebral arteries.
V./3.1.4.2. Arterial supply territories
Knowledge of each artery-belonging supply territories is important regarding the detection.
V./3.1.4.3.: Topography of embolism sources
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Regarding thromboembolism, the most frequent source is the cardiac embolism (atrial fibrillation > thrombus formation > embolisation). It is characterized by multiplicity. In case of bilateral infarcts we can surely state that emboli have a cardiac (left atrium) origin. Emboli might originate from the aorta and from the cervical arteries (so-called arterio-arterial embolisation) as well, however high grade stenosis/occlusion of the cervical arteries (internal carotid artery) due to arteriosclerotic origin is not rare. Embolic occlusion of middle cerebral artery, anterior cerebral artery (pericallosal artery), posterior cerebral artery (basilar artery), lenticulostriatal arteries and the cerebral arteries are the most frequent ones.
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