Slowly progressive spread of the stroke-like lesions in MELAS

Background: Little is known about temporal and spatial progression of the stroke-like lesion during the acute stage of the stroke-like episode in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Methods: In four stroke-like episodes of MELAS observed in three patients, MRI, EEG, and SPECT were studied consecutively within the first month of the onset. Results: The first presenting symptoms were headache in all four stroke-like episodes, followed by hemianopsia, psychosis, and aphasia. In three episodes, epileptic seizure developed subsequently in close association with a progression of stroke-like lesion. In all four episodes, serial MRI showed a slowly progressive spread of the stroke-like lesion evolving from the temporal cortex to the surrounding parietal or occipital cortex over a few weeks following the onset of initial symptoms. Apparent diffusion coefficient (ADC) maps showed slightly decreased ADC values in the actively evolving brain lesions compared with those in nonaffected regions of the brain. EEG showed a pattern of focal periodic epileptiform discharges in three episodes. SPECT showed a focal hyperemia in all four stroke-like lesions, in two of which focal hyperemia persisted for the first month. A T1-weighted hyperintense cortical signal on MRI compatible with cortical laminar necrosis was seen during the subacute stage of all stroke-like lesions. Conclusion: Slowly and progressively spreading stroke-like lesions on MRI may reflect ongoing neuronal metabolic derangement associated with concomitant vasogenic edema provoked by prolonged epileptic seizure activities.