Borderzone territory

Fig. 15.7. The theoretical concepts of stroke in hemodynamic risk zones - dot-like microembolic lesions in the most distal arterial branches resulting from more proximal vessel pathology and impaired emboli washout (left) and the complete infarction of the compromised tissue in the borderzone territory (right). The bottom row gives DWI examples of these lesion patterns...

MCA infarcts are mainly caused by cardioembolism, internal carotid artery (ICA) thrombosis, dissection or embolism and rarely (in Caucasians) by intrinsic MCA disease. MCA atherothrombotic territory infarctions related to intrinsic MCA disease often cause concomitant small cortical (territorial or borderzone) and subcortical infarcts (Min et al. 2000). 

Cerebellar infarcts can be grouped in territorial (superior cerebellar artery, anterior inferior cerebellar artery, posterior inferior cerebellar artery and combined), borderzone and lacunar. They are often combined with brain stem infarcts and with superficial posterior cerebral artery or thalamic infarcts. The most common isolated cerebellar infarcts are located in the superior cerebellar artery and posterior inferior cerebellar artery territories (Amarenco 1993 Amarenco et al. 1993,1994). 

Lee PH, Bang OY, Oh SH et al (2003) Subcortical white matter infarcts. Comparison of superficial perforating artery and internal borderzone infarcts using diffusion-weighted magnetic resonance imaging. Stroke 34 2630-2635 Leys D, Mounier-Vehier F, Lavenu I et al (1994) Anterior choroidal artery territory infarcts. Study of presumed mechanisms. Stroke 25 837-842... 

In the past, two different basic mechanisms have been proposed to account for ischemic events in ICA occlusive disease (1) intracranial embolism and (2) a low-perfusion state also referred to as hemodynamic insufficiency. In the post-mortem arteriographic and pathologic study by Rodda and Path (1986), massive infarcts involving two major cerebral artery territories were associated with distal ICA occlusion, middle cerebral artery (MCA) territory infarcts were seen when the ICA was occluded or stenosed, and borderzone infarcts were characterized by ICA disease and limited circle of Willis anastomosis. 

Fig 15.1. Diffusion-weighted imaging demonstrates different patterns of acute stroke in occlusive internal carotid artery disease 1, territorial stroke 2, subcortical stroke 3, territorial stroke with fragmentation 4, disseminated small lesions 5, borderzone infarction... 

Kang et al. (2002) 35 > 70% or occlusion Territorial lesion (n=21) Borderzone lesion with or without a territorial lesion (n=10) Bilateral hemispheric lesions (n=4) Acute ischemic lesion in ICA occlusive disease is mainly multiple borderzone infarction was mostly associated with territorial infarction... 

Szabo et al. (2001) 102 >50 or occlusion Territorial stroke (n=30) Subcortical stroke ( =13) Territorial infarction with fragmentation (n=ll) Disseminated small lesions (n=15) Borderzone lesions (n=33) The degree of ICA stenosis may favor certain stroke patterns. In patients with high-grade stenosis the highest frequency of lesions occurs in the hemodynamic risk zones... 

Yet, since the territories of the major cerebral arteries have been shown to possibly vary considerably, lesion localization alone may not be enough to identify borderzone lesions. Van der Zwaan and Hillen (1991) described different variations of the cortical distributions in all 25 human brains obtained at autopsy through injecting different colored substances into the six major arteries of the human brain. He also noted an inter-individual difference with remarkable asymmetrical territorial distribution in both hemispheres. With the clinical use of novel MRI techniques, however, it is possible to identify acute ischemic lesions in individual hemodynamic risk zones. 

Fig. 15.1 la-d. A 62-year-old patient with symptomatic left internal carotid artery occlusion and progressive stroke. Initial DWI shows only punctuate small lesions in the deep borderzone of the left hemisphere (a), while the hypoperfused area on the time-to-peak maps affects the complete left middle cerebral artery territory and is most pronounced in the deep borderzone area (b). On day 3, the acute lesion has grown considerably larger, paralleling progression of symptoms (c). Contrast-enhanced MRA shows proximal occlusion of the left internal carotid artery (d)... 

The watershed areas (see Chap. 15) are particularly sensitive to ischemia in cardiac arrest, especially in the parietal lobe area in the borderzone between anterior, posterior and middle cerebral artery territories. 

Rigo, E. (2011) Citizens despite Borders Challenges to the Territorial Order of Europe. Pp. 199-215 in V. Squire (ed.). The Contested Politics of Mobility Borderzones and Irregularity. London Routledge. 

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