Ischemic stroke etiology

Copen WA, Schwamm LH, Gonzalez RG, Wu O, Harmath CB, Schaefer PW, Koroshetz WJ, Sorensen AG. Ischemic stroke effects of etiology and patient age on the time course of the core apparent diffusion coefficient. Radiology 2001 221 27-34. 

Although several approaches to stroke classification have been described, the most common mechanism-based classification in current use is the system described by the TOAST investigators." This classification describes five major subtypes of ischemic stroke based on the results of neuroimaging and other medical investigations, namely (1) LAA, (2) cardioembolism, (3) small-vessel occlusion, (4) stroke of other determined etiology, and (5) stroke of undetermined etiology. Inter-rater reliability of the TOAST scheme has been reported as moderate-to-substantial K 0.5-0.7). 

Ischemic strokes account for 88% of all strokes and are due either to local thrombus formation or to emboli that occlude a cerebral artery. Cerebral atherosclerosis is a causative factor in most cases of ischemic stroke, although 30% are of unknown etiology. Emboli can arise either from intra- or extracranial arteries. Twenty percent of embolic strokes arise from the heart. 

Approximately 25% of ischemic strokes are caused by identifiable atherothromboem-bolism from large artery disease, 25% by small vessel disease, 20% by cardioembolism, approximately 5% by rarities, and the remainder are of undetermined etiology (Schulz and Rothwell 2003) (Table 6.2). 

The four main classifications described above (Bamford et al. 1991 Mead et al. 1999) are clinical and can be determined at the bedside and following the results of brain imaging. Further classification is possible in ischemic stroke by etiology, and this is most commonly done according to the TOAST criteria. 

Some overlap exists between the clinical classification (Bamford et al. 1991) and the etiological TOAST classification. In a large hospital-based series of patients with ischemic stroke, total and partial anterior circulation infarcts were most likely to be caused by large artery atherosclerosis, cardioembolism or both (Wardlaw et al. 1999). 

Antiplatelet therapy reduces the risk of recurrent vascular events after TIA and ischemic stroke, although few trials have distinguished between different etiological subtypes (Antithrombotic Trialists Collaboration 2002). Most trial data concern aspirin, but other antiplatelet agents such as clopidogrel (CAPRIE Steering Committee 1996) or extended-release dipyridamole (Sivenius et al. 1991) have also been shown to be effective although mechanisms of action may differ (Table 24.2). 

No significant relation between Hey and ischemic stroke was observed in this cohort. However, its etiological importance may be greater for premature ischemic strokes (<65 years). 

Compared with brain ischemia spinal cord strokes are caused by more diverse etiologies. Up-to-now there is no satisfactory and accepted classification of spinal infarcts. Etiologies include circulatory arterial and venous disorders. From a clinical and pathoanatomical point of view it seems reasonable to differentiate between acute ischemic myelomalacia and subacute to chronic vascular myelopathy (Table 17.1). In most cases MRI enables the differentiation of these two main etiologies. A deficient spinal arterial blood flow generally has various causes, ranging from the occlusion of intercostal or lumbar arteries to affection of the intrinsic arteries of the spinal cord. ... 

The general treatments described in this chapter are applicable to all patients with acute major stroke regardless of etiology. Specific treatment for ischemic and hemorrhagic stroke is discussed in Chs. 21 and 22, respectively. Therapy for acute stroke can be divided into ... 

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