Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke -like episodes (MELAS) syndrome in adult: a case report with literature review

Objective: To investigate the clinical and imaging characteristics of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome in adult, and to enhance the knowledge of this disease and decrease misdiagnose. Methods: Relevant literatures were reviewed, and two cases of MELAS syndrome proved by muscle pathology were retrospectively analyzed. Results: The two patients presented with the onset of stroke and seizures. Imaging examination: 'cerebral infarction'-like lesions asymmetrically involving temporal parietal occipital lobe. CT scan showed patchy low density shadow. On MRI, lesions showed slightly long T₁ and T₂ signals, hyperintensity on FLAIR and DWI, slightly low signal on ADC map. The lesions involved the territories of middle cerebral artery and the posterior cerebral artery. Brain MRA scan showed supply artery stenosis or occlusion. The perfusion weighted imaging showed abnormal hyperperfusion in the lesion area. Magnetic resonance spectroscopy (TE = 135 ms) scan showed obvious inverted lactate peak at lesions. Laboratory tests showed the lactate level of blood and cerebrospinal fluid increased significantly. For biceps brachii biopsy, the scattered and ragged red fibers can be seenon modified Gomori-trichrome. The two cases of last diagnosis is MELAS syndrome. For the mt DNA A3243G of detection, the first case was negative, but the second case was positive. The first patient returned one year later due to second onset, the new lesion involved temporal pole, brain atrophy was seen at the primary lesion area. Conclusion: MELAS syndrome is rare in clinic, and clinical and imaging manifestations have certain characteristics. Multimodality MRI has important value in the diagnosis of the disease. Final diagnosis relies on muscle histological examination. (authors)