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Serial diffusion-weighted imaging in MELAS
1Third Department of Internal Medicine, Hiroshima University School of Medicine, Japan. ohshitat@mcai.med.hiroshima-u.ac.jp
Abstract:
Clinical features of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) resemble those of cerebral infarcts, but the pathogenesis of infarct-like lesions is not fully understood. To characterise these infarct-like lesions, we studied two patients with MELAS using diffusion-weighted (DWI) MRI before and after stroke-like episodes and measured the apparent diffusion coefficient (ADC) in the new infarct-like lesions. These gave high signal on DWI and had much higher ADC than normal-appearing regions. The ADC remained high even 30 days after a stroke-like episode then decreased in lesions, with or without abnormality as shown by conventional MRI. We speculate that early elevation of ADC in the acute or subacute phase reflects vasogenic rather than cytotoxic edema. The ADC of the lesions, which disappeared almost completely with clinical improvement, returned to normal levels, which may reflect tissue recovery without severe damage. To our knowledge, this is the first study of DWI in MELAS.
Insights
Diffusion-weighted MRI in mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) reveals elevated apparent diffusion coefficient (ADC) in lesions, suggesting vasogenic edema and potential tissue recovery without severe damage.
Area of Science:
- Neurology
- Radiology
- Mitochondrial Diseases
Background:
- Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) present with infarct-like brain lesions.
- The precise pathogenesis of these lesions remains unclear.
Observation:
- This study utilized diffusion-weighted imaging (DWI) MRI in two MELAS patients.
- Apparent diffusion coefficient (ADC) was measured in acute and subacute infarct-like lesions.
- Lesions showed high DWI signal and significantly elevated ADC compared to normal brain tissue.
Findings:
- Elevated ADC persisted for at least 30 days post-episode, decreasing over time.
- The initial ADC elevation is hypothesized to represent vasogenic edema.
- Lesion ADC normalized with clinical improvement, indicating tissue recovery.
Implications:
- This is the first study to apply DWI in MELAS patients.
- DWI and ADC mapping may offer insights into MELAS lesion pathogenesis and recovery.
- Findings suggest a potential for reversible tissue changes in MELAS stroke-like episodes.