Serial brain imaging analysis of stroke-like episodes in MELAS
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Updated: Jul 7, 2026
Integrated Photoacoustic, Ultrasound, and Angiographic Tomography (PAUSAT) for NonInvasive Whole-Brain Imaging of Ischemic Stroke
Published on: June 2, 2023
Hiromichi Ito1, Kenji Mori, Masafumi Harada
1Department of Pediatrics, School of Medicine, University of Tokushima, 3-18-15, Kuramoto-Cho, Tokushima 770-8503, Japan. michiito@lime.ocn.ne.jp
Abstract:
We report 2 patients of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and consider the pathophysiology of stroke-like lesions, using magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI) on MRI, perfusion imaging on MRI, and 1H magnetic resonance spectroscopy (1H-MRS). In Patient 1, T2-weighted imaging (T2-WI) on MRI at onset and even at 44 days after onset of the stroke-like episode showed high intensity in left parietal, temporal, and occipital lobe lesions. In the temporal lobe lesion, the apparent diffusion coefficient (ADC) at 44 days after onset was higher (average: 1.219x10(-3)mm2/s) than that in a normal region (average: 0.796x10(-3)mm2/s). (1)H-MRS of the left parietal lobe lesion at the same day showed a decrease in N-acetylaspartate/(creatine+phosphocreatine) (NAA/Cr) (0.43) and a peak in lactate. 1H-MRS of the contralateral side at the same day showed NAA/Cr (1.57) and no peak in lactate. Thereafter, ADC gradually decreased and NAA/Cr gradually increased, and the peak in lactate disappeared in the lesion. In Patient 2, T2-WI at onset showed high intensity in bilateral occipital lobe lesions. In the left occipital lobe lesion, ADC at the same day was higher (1.082x10(-3)mm2/s) than that in a normal region (average: 0.841x10(-3)mm2/s). (1)H-MRS of the left occipital lobe lesion at the same day showed a decrease of NAA (3.0mM) and a peak in lactate (13.1mM) (measured by LCModel). In 1H-MRS of the normal left parietooccipital lobe at 4 months before onset, NAA was 7.6mM and there was no peak in lactate (0mM). Perfusion imaging at onset showed high intensity in bilateral occipital lobes, which indicated hyperperfusion in stroke-like lesions. Thereafter, ADC gradually decreased and the peak in lactate partially decreased, and the low concentration of NAA persisted (regardless of the partial recovery) in the lesion. These results suggest that the stroke-like episodes is related to vasogenic edema, hyperperfusion, and neuronal damage. Acute oxidative phosphorylation defect may have a crucial role in the pathophysiology of stroke-like episodes.
Insights
Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) involves stroke-like lesions. Imaging reveals vasogenic edema, hyperperfusion, and neuronal damage, suggesting acute oxidative phosphorylation defects play a key role.
Area of Science:
- Neurology
- Radiology
- Genetics
Background:
- Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a rare mitochondrial disorder.
- Stroke-like lesions are a common manifestation of MELAS, but their pathophysiology is not fully understood.
Observation:
- Two patients with MELAS presented with stroke-like lesions.
- Magnetic resonance imaging (MRI) techniques including diffusion-weighted imaging (DWI), perfusion imaging, and 1H magnetic resonance spectroscopy (1H-MRS) were used to evaluate the lesions.
- Imaging revealed vasogenic edema, hyperperfusion, and neuronal damage in the affected brain regions.
Findings:
- Apparent diffusion coefficient (ADC) values were elevated in the lesions, indicating edema.
- 1H-MRS showed decreased N-acetylaspartate (NAA) and increased lactate, consistent with neuronal damage and altered metabolism.
- Perfusion imaging demonstrated hyperperfusion in the stroke-like lesions.
Implications:
- The findings suggest that stroke-like episodes in MELAS are related to a combination of vasogenic edema, hyperperfusion, and neuronal damage.
- Acute oxidative phosphorylation defects are implicated as a crucial factor in the pathophysiology of these stroke-like episodes.
- Further research into the mechanisms underlying stroke-like lesions in MELAS may lead to improved diagnostic and therapeutic strategies.
