Serial diffusion-weighted imaging in a patient with MELAS and presumed cytotoxic oedema

Abstract

A patient with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) was studied with serial diffusion-weighted MRI (DWI) after stroke-like episodes and the apparent diffusion coefficient (ADC) was measured in an infarct-like lesion. In the acute and subacute stages, the affected area gave high signal on DWI and its ADC was much lower than that in a normal control region. In the chronic stage, the ADC became higher than that in normal brain. We therefore suggest that the stroke-like episodes did not cause vasogenic oedema but were related to energy failure and cytotoxic oedema.

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

“…All studies reporting low ADC have a short onset-MRI interval, and follow-up shows gradual ADC increase within days to weeks (Table). 3,4,10 Some studies reporting normal or high ADC also have short intervals (Table). 2,6 -9 This apparent contradiction may, however, reflect the difficulties with precisely defining onset of a SLL.…”

“…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.…”

Central Nervous System Imaging in Mitochondrial Disorders

“…Unique features of SLLs in the acute stage, in addition to progressive spread, are focal periodic epileptiform discharges, focal hyperperfusion, seen on SPECT studies 24 and perfusion weighted MRI, and laminar cortical necrosis (LCN) 24 . Some reports also demonstrated restricted diffusion within SLLs [32][33][34][35] . The SLLs usually progress up to several weeks after onset 36 hypesthesia, which often disappear without sequelae or seizures 37 .…”

“…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 .…”

“…Similar but less prominent alterations can be found in the grey matter 67 . The most frequent finding on MRS in MCD with CNS involvement is an increased lactate peak 15,18,33,65,[68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83] , which may precede the SLLs 15 . High levels of intra-ventricular lactate are usually associated with severe neurologic impairment 6 .…”