Diffusion and Perfusion Characteristics of MELAS (Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-Like Episode) in Thirteen Patients

Abstract

ObjectiveWe analyzed the diffusion and perfusion characteristics of acute MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode) lesions in a large series to investigate the controversial changes of the apparent diffusion coefficient (ADC) that were reported in prior studies.Materials and MethodsWe analyzed 44 newly appearing lesions during 28 stroke-like episodes in 13 patients with MELAS. We performed a visual assessment of the MR images including the ADC and perfusion maps, comparison of the ADC between the normal and abnormal areas, comparison of % ADC between the 44 MELAS lesions and the 30 acute ischemic infarcts. In addition, the patterns of evolution on follow-up MR images were analyzed.ResultsDecreased, increased, and normal ADCs were noted in 16 (36%), 16 (36%), and 12 (27%) lesions, respectively. The mean % ADC was 102 ± 40.9% in the MELAS and 64 ± 17.8% in the acute vascular infarcts (p < 0.001), while perfusion imaging demonstrated hyper-perfusion in six acute MELAS lesions. On follow-up images, resolution, progression, and tissue loss were noted in 10, 4, and 17 lesions, respectively.ConclusionThe cytotoxic edema gradually evolves following an acute stroke-like episode in patients with MELAS, and this may overlap with hyper-perfusion and vasogenic edema. The edematous swelling may be reversible or it may evolve to encephalomalacia, suggesting irreversible damage.

MR evaluation of cerebral oxygen metabolism and blood flow in stroke-like episodes of MELAS

“…Many studies have shown almost consistent results regarding the perfusion status around the time of a stroke: i.e., hyperperfusion in the acute stage followed by hypoperfusion in the subacute and chronic stages [9,11,16,[20][21]. Our study revealed similar lesion-associated chronological changes in CBF.…”

Response of the authors to the comments of Josef Josef Finsterer and Sinda Zarrouk-Mahjoub on NeuroImage “Cerebral arterial and venous MRI abnormalities in MELAS”

“…Concerning the possible role of seizures and/or SLE treatment in the arterial abnormalities reported, in our opinion, this seems unlikely, since two of the three patients lacked clinical and EEG abnormalities in favor of epilepsy, and arterial abnormalities were restricted to the brain areas involved by the SLE. One might suspect a more diffuse cerebral artery dilatation in treatment-induced perfusion abnormalities, although an interaction between SLE treatment therapies and cerebral arteries only involved in the SLE cannot be excluded.The variability of signal changes on ADC map in SLE in our three patients corresponded well to the earlier reports analyzing ADC in SLE showing cortical hypo-, iso-, or hyperintensities during SLE, probably also depending on the timing of MRI performance (and the stage of SLE) [1,2]. …”

“…The variability of signal changes on ADC map in SLE in our three patients corresponded well to the earlier reports analyzing ADC in SLE showing cortical hypo-, iso-, or hyperintensities during SLE, probably also depending on the timing of MRI performance (and the stage of SLE) [1,2].…”

Migratory stroke-like lesions in a case of adult-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome and a review of imaging findings

“…Global atrophy and calcification of the basal ganglia are sometimes present [16]. MRI characteristically shows hyperintensity on diffusion weighted imaging and FLAIR with a predilection for the parietal, temporal, and occipital cortex, without conforming to a single vascular territory, a hallmark finding of MELAS [19], [20], [21]. Blood vessels typically are normal on angiographic evaluation, although cases of vasoconstriction have been reported [22].…”