Abstract
ObjectiveTo quantify the cerebral OEF at different phases of stroke-like episodes in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) by using MRI.MethodsWe recruited 32 patients with MELAS confirmed by gene analysis. Conventional MRI scanning, as well as functional MRI including arterial spin labeling and oxygen extraction fraction imaging, was undertaken to obtain the pathological and metabolic information of the brains at different stages of stroke-like episodes in patients. A total of 16 MRI examinations at the acute and subacute phase and 19 examinations at the interictal phase were performed. In addition, 24 healthy volunteers were recruited for control subjects. Six regions of interest were placed in the anterior, middle, and posterior parts of the bilateral hemispheres to measure the OEF of the brain or the lesions.ResultsOEF was reduced significantly in brains of patients at both the acute and subacute phase (0.266 ± 0.026) and at the interictal phase (0.295 ± 0.009), compared with normal controls (0.316 ± 0.025). In the brains at the acute and subacute phase of the episode, 13 ROIs were prescribed on the stroke-like lesions, which showed decreased OEF compared with the contralateral spared brain regions. Increased blood flow was revealed in the stroke-like lesions at the acute and subacute phase, which was confined to the lesions.ConclusionMRI can quantitatively show changes in OEF at different phases of stroke-like episodes. The utilization of oxygen in the brain seems to be reduced more severely after the onset of episodes in MELAS, especially for those brain tissues involved in the episodes.
Highlights
Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a common type of mitochondrial disorder, characterized by neurological remissions and relapses, associated with progressive neurocognitive deficits [1]
The cerebral oxygen extraction fraction (OEF) values of all regions of interest (ROI) in the controls were pooled to define the normal range of cerebral OEF, which was 0.316±0.025 with a 95% confidence interval of 0.306-0.327
The cerebral OEF values were 0.266±0.026 in group A and 0.295±0.009 in group B, which were significantly decreased compared with the control group (X2=25.800, P
Summary
Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a common type of mitochondrial disorder, characterized by neurological remissions and relapses, associated with progressive neurocognitive deficits [1]. Patients present with severe symptoms such as hemiparesis, altered consciousness, vision abnormalities after the acute onsets of stroke-like episodes. These symptoms may gradually resolve at the subacute phase. The stroke-like episodes are often followed by a complete recovery at the interictal phase. A mitochondrial DNA point mutation is most often the underlying genetic factor of the disease, which causes a failure of mitochondrial protein synthesis resulting in impaired ATP production. 80% of MELAS cases are associated with the mutation of mitochondrial DNA A3243G, and various other mutations have been reported [2]
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