Ito Hiromichi, Mori Kenji, Kagami Shoji
Department of Pediatrics, School of Medicine, University of Tokushima, Japan.
Brain Dev. 2011 Apr;33(4):283-8. doi: 10.1016/j.braindev.2010.06.010. Epub 2010 Jul 6.
Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) shows sudden neurological deficits that are called 'stroke-like episodes'. With regard to the pathophysiology of stroke-like episodes, so-called mitochondrial angiopathy and cytopathy theories have been proposed, but the subject is still controversial. To clarify this matter and to contribute to the development of a treatment for MELAS, we review here current neuroimaging research and consider the pathophysiology of stroke-like lesions. With regard to diffusion-weighted imaging findings, early reports often showed an elevated apparent diffusion coefficient (ADC) in stroke-like lesions; this was considered to be mainly vasogenic edema in the acute phase and is a different pattern than that in stroke. However, there has recently been an increase in the number of reports of a decrease in ADC; these cases are considered to be cytotoxic edema in the acute phase, which is compatible with stroke. With regard to (1)H-magnetic resonance spectroscopy findings in stroke-like lesions, a decrease in N-acetylaspartate and an increase in lactate have been reported. With regard to single photon emission computed tomography findings for stroke-like lesions in MELAS, an overall trend is hyperperfusion in the acute stage (within 1 month) of stroke-like episodes and hypoperfusion in the chronic stage (several months later). With regard to positron emission tomography, nearly all of these reports are consistent with the mitochondrial cytopathy theory. With regard to neuropathology in MELAS, the most common findings during the chronic stage of stroke-like episodes include foci of necrosis and peculiar vascular changes (abnormalities of mitochondria in small arteries). Concerning the pathology of the acute stage of stroke-like episodes, extensive petechial hemorrhage along the gyri of the cortex corresponding to acute stroke-like lesions has been reported. To clarify the true pathophysiology of stroke-like episodes, we offer three suggestions. First, we must define the precise onset of stroke-like episodes. Second, current studies are limited by the difficulty of imaging just before and just after (within a few minutes) the onset of stroke-like episodes. Third, we hope to establish an experimental animal model. We should conduct a simultaneous multimodal imaging and histological study just before and just after (within a few minutes) the onset of stroke-like episodes in an experimental animal model.
线粒体肌病、脑病、乳酸酸中毒和卒中样发作（MELAS）表现为突发的神经功能缺损，即所谓的“卒中样发作”。关于卒中样发作的病理生理学，已提出所谓的线粒体血管病和细胞病理论，但该问题仍存在争议。为阐明这一问题并推动MELAS治疗方法的发展，我们在此回顾当前的神经影像学研究，并探讨卒中样病变的病理生理学。关于扩散加权成像结果，早期报告常显示卒中样病变的表观扩散系数（ADC）升高；这被认为主要是急性期的血管源性水肿，与卒中的表现模式不同。然而，最近报告中ADC降低的情况有所增加；这些病例被认为是急性期的细胞毒性水肿，与卒中相符。关于卒中样病变的氢磁共振波谱结果，已报告N-乙酰天门冬氨酸减少和乳酸增加。关于MELAS中卒中样病变的单光子发射计算机断层扫描结果，总体趋势是卒中样发作急性期（1个月内）血流灌注增加，慢性期（数月后）血流灌注减少。关于正电子发射断层扫描，几乎所有这些报告都与线粒体细胞病理论一致。关于MELAS的神经病理学，卒中样发作慢性期最常见的发现包括坏死灶和特殊的血管变化（小动脉线粒体异常）。关于卒中样发作急性期的病理学，已报告对应急性卒中样病变的皮质脑回沿线广泛的瘀点性出血。为阐明卒中样发作的真正病理生理学，我们提出三点建议。首先，我们必须明确卒中样发作的确切起始时间。其次，目前的研究受到在卒中样发作起始前和起始后几分钟内进行成像的困难的限制。第三，我们希望建立实验动物模型。我们应该在实验动物模型中，在卒中样发作起始前和起始后几分钟内同时进行多模态成像和组织学研究。
