Serial diffusion-weighted imaging in MELAS

Abstract

Clinical features of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) resemble those of cerebral infarcts, but the pathogenesis of infarct-like lesions is not fully understood. To characterise these infarct-like lesions, we studied two patients with MELAS using diffusion-weighted (DWI) MRI before and after stroke-like episodes and measured the apparent diffusion coefficient (ADC) in the new infarct-like lesions. These gave high signal on DWI and had much higher ADC than normal-appearing regions. The ADC remained high even 30 days after a stroke-like episode then decreased in lesions, with or without abnormality as shown by conventional MRI. We speculate that early elevation of ADC in the acute or subacute phase reflects vasogenic rather than cytotoxic edema. The ADC of the lesions, which disappeared almost completely with clinical improvement, returned to normal levels, which may reflect tissue recovery without severe damage. To our knowledge, this is the first study of DWI in MELAS.

Central Nervous System Imaging in Mitochondrial Disorders

“…In the acute stage SLLs present as T2-hyperintensities, particularly located in the occipital, parietal, or temporal lobes but occasionally also in the frontal areas ( Figure 2) [25][26][27][28][29] . Occasionally, also the deep grey matter may be involved ( Figure 3).…”

“…Acute SLLs manifest on MRI as widespread T2-hyperintensities particularly in the temporo-parietal region 50 . On diffusion weighted imaging (DWI) SLLs present as hyperintensities [27][28][29]33,35,64,65 . Diffusion weighted imaging is regarded as more sensitive than T2-weighted images to demonstrate SLLs 15 .…”

Serial Diffusion Imaging in a Case of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes

“…1 Diffusionweighted imaging (DWI) shows high signal in the acute phase that normalizes progressively over time. [1][2][3][4][5] Most studies also report increased apparent diffusion coefficient (ADC) in the acute phase of the stroke-like episode (Table), and this has been used to distinguish stroke-like lesions (SLL) from ischemic lesions. 1,2,[5][6][7][8][9] However, at least 3 cases of low SLL ADC have been reported (Table).…”

“…[1][2][3][4][5] Most studies also report increased apparent diffusion coefficient (ADC) in the acute phase of the stroke-like episode (Table), and this has been used to distinguish stroke-like lesions (SLL) from ischemic lesions. 1,2,[5][6][7][8][9] However, at least 3 cases of low SLL ADC have been reported (Table). 3,4,10 We performed multiple sequential MRI examinations covering 2 stroke-like episodes in a patient with MELAS to investigate the diffusion properties and evolution of the SLL.…”

Strokes in mitochondrial diseases

“…ADCs был нормальным [39] или повы-шенным [40,41] в пораженных при инсультоподобных эпи-зодах областях головного мозга, однако описано также сни-жение ADCs [40]. В большинстве исследований показано повышение коэффициента диффузии в острую фазу ин-сультоподобных эпизодов, что является отличием этих эпи-зодов от ишемического инсульта [39,[42][43][44][45][46][47].…”