Mechanisms of acute cerebral infarctions in patients with middle cerebral artery stenosis: A diffusion‐weighted imaging and microemboli monitoring study

Abstract

Although most therapeutic efforts and experimental stroke models focus on the concept of complete occlusion of the middle cerebral artery as a result of embolism from the carotid artery or cardiac chamber, relatively little is known about the stroke mechanism of intrinsic middle cerebral artery stenosis. Differences in stroke pathophysiology may require different strategies for prevention and treatment. We prospectively studied 30 consecutive acute ischemic stroke patients with middle cerebral artery stenosis detected by transcranial Doppler and magnetic resonance angiography. Patients underwent microembolic signal monitoring by transcranial Doppler and diffusion-weighted magnetic resonance imaging. Characteristics of acute infarct on diffusion-weighted magnetic resonance imaging were categorized according to the number (single or multiple infarcts) and the pattern of cerebral infarcts (cortical, border zone, or perforating artery territory infarcts). The data of microembolic signals and diffusion-weighted magnetic resonance imaging were assessed blindly and independently by separate observers. Diffusion-weighted magnetic resonance imaging showed that 15 patients (50%) had single acute cerebral infarcts and 15 patients had multiple acute cerebral infarcts. Among patients with multiple acute infarcts, unilateral, deep, chainlike border zone infarcts were the most common pattern (11 patients, 73%), and for single infarcts, penetrating artery infarcts were the most common (10 patients, 67%). Microembolic signals were detected in 10 patients (33%). The median number of microembolic signals per 30 minutes was 15 (range, 3-102). Microembolic signals were found in 9 patients with multiple infarcts and in 1 patient with a single infarct (p = 0.002, chi(2)). The number of microembolic signals predicted the number of acute infarcts on diffusion-weighted magnetic resonance imaging (linear regression, adjusted R(2) =0.475, p < 0.001). Common stroke mechanisms in patients with middle cerebral artery stenosis are the occlusion of a single penetrating artery to produce a small subcortical lacuna-like infarct and an artery-to-artery embolism with impaired clearance of emboli that produces multiple small cerebral infarcts, especially along the border zone region.

A study of microemboli monitoring of atherosclerotic thrombotic cerebral infarction and artery stenosis

“…Since then, TCD microemboli are often used in cerebral angiography, carotid artery stenting, carotid endarterectomy, and as monitoring indicators preventing thrombotic events in surgery. Studies have shown that the presence of microemboli is related to the lesion numbers shown by MRI (magnetic resonance imaging) and DWI (diffusion-weighted imaging) and the lesion characteristics in the skull of patients with cerebral infarction (Kimura et al, 2001;Wong et al, 2002;Nakajima et al, 2007). The recurrence probability of cerebral infarction increased in microembolus-positive patients (Valton et al, 1998;Nakajima et al, 2007;Iguchi et al, 2007).…”

Microemboli Monitoring in Ischemic Stroke

“…The available data shows that the prevalence of microemboli in intracranial stenosis to be between 7-33% (Nabavi, Georgiadis et al 1996;Segura, Serena et al 2001;Wong, Gao et al 2001;Droste, Junker et al 2002;Wong, Gao et al 2002;Gao, Wong et al 2004). The prevalence of microemboli in the largest of those studies (n=114) was 22%.…”

“…Even though there are technical difficulties in performing microemboli monitoring in the presence of intracranial stenosis, the presence of microemboli provides valuable information to choose appropriate www.intechopen.com management. The frequency of microemboli in the presence of intracranial artery stenosis has shown to be associated with the number of infarcts on imaging (Wong, Gao et al 2002).…”

Neuroimaging - Clinical Applications

“…The underlying mechanisms leading to ischemia in the diseased arterial territory include artery-to-artery embolism, thrombosis leading to complete occlusion or to local branch occlusion and hemodynamic compromise (Wong et al, 2002). A combination of these factors may also co-exist in some patients.…”