Acute Cortical Lesions in MELAS Syndrome: Anatomic Distribution, Symmetry, and Evolution

Abstract

BACKGROUND AND PURPOSE: Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome is a rare mitochondrial disorder affecting children and young adults. Stroke-like episodes are often associated with acute cortical lesions in the posterior cerebral cortex and are classically described as asymmetric and transient. In this study we assessed the anatomic distribution of acute cortical lesions, the incidence of symmetry, and the temporal evolution of lesions. MATERIALS AND METHODS:This was a retrospective cohort study of patients who had a confirmed genetic diagnosis of a pathogenic variant associated with MELAS and MR imaging performed at our center (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018). Each MR imaging study was assessed for new lesions using T1, T2, FLAIR, DWI, ADC, and SWI. The anatomic location, symmetry, and temporal evolution of lesions were analyzed.RESULTS: Eight patients with the same pathogenic variant of MELAS (MT-TL1 m.3243A.G) with 31 MR imaging studies were included. Forty-one new lesions were identified in 17 of the studies (5 deep, 36 cortical). Cortical lesions most commonly affected the primary visual cortex, the middle-third of the primary somatosensory cortex, and the primary auditory cortex. Thirty of 36 cortical lesions had acute cortical diffusion restriction, of which 21 developed cortical laminar necrosis on subacute imaging. Six of 11 studies with multiple lesions showed symmetric cortical involvement.

Altered Dynamic Functional Connectivity in Patients With Mitochondrial Encephalomyopathy With Lactic Acidosis and Stroke‐Like Episodes (MELAS) at Acute and Chronic Stages: Shared and Specific Brain Connectivity Abnormalities

“…Acute SLLs of each MELAS patient at the acute stage and chronic SLLs of each MELAS patient at the chronic stage were identified and manually segmented on FLAIR images slice‐by‐slice using the medical imaging interaction toolkit (MITK) software (http://www.mitk.org/wiki/MITK) 32 by an experienced radiologist with 10 years' experience in MELAS (YX.L.). Acute SLLs are defined as fresh ischemic‐like lesions showing gyral swelling and subcortical white matter hyperintensity on FLAIR, and chronic SLLs are characterized by areas of encephalomalacia, cortical thinning, and hyperintensity on FLAIR 33 . SLL mask images were then spatially normalized to the standard MNI space.…”

Stroke-like Episodes in m.3243A≥G Carriers Need to Be Monitored by MRI Starting with the Onset of Clinical Manifestations

“…In Table 2, the authors differentiate between "ADC prior low" and "ADC prior normal/high." 1 However, in none of the cases is the ADC during the first week described as normal/ high. 1 Only low ADC values are mentioned.…”

“…1 However, in none of the cases is the ADC during the first week described as normal/ high. 1 Only low ADC values are mentioned. This discrepancy requires clarification.…”

“…It was found that among 31 imaging studies, performed between 2006 and 2018, forty-one lesions were "new" in 17 studies. 1 It was concluded that cortical lesions most commonly affect the primary visual, the primary somatosensory, and the primary auditory cortices. 1 The study has a number of limitations and shortcomings.…”

“…The other 16 studies were follow-ups (n = 15) or screening (n = 1). 1 In contrast, 41 T2-hyperintense lesions were found in the acute stage according to Table 2, suggesting that the 16 studies without an acute indication were also included in this evaluation. This discrepancy requires clarification.…”