Alzheimer's disease(AD)is the most common neurodegenerative disorder leading to dementia in the elderly,characterized by a gradual decline in cognitive function and daily living abilities.The pathogenesis of AD remains unclear,and the efficacy of existing pharmacological treatments is limited,making the search for new therapeutic approaches imperative.Current research suggests that transcranial alternating current stimulation(tACS)can ameliorate cognitive deficits in AD,potentially due to its ability to modulate single or nested brain rhythms,local or distant synchronization,and metabolic activity,which can influence cognitive functions.This review summarizes the research progress of tACS in the treatment of AD,aiming to provide new insights into the exploration of the pathogenesis and treatment of AD.

Alzheimer's disease(AD)is the most common neurodegenerative disorder leading to dementia in the elderly,characterized by a gradual decline in cognitive function and daily living abilities.The pathogenesis of AD remains unclear,and the efficacy of existing pharmacological treatments is limited,making the search for new therapeutic approaches imperative.Current research suggests that transcranial alternating current stimulation(tACS)can ameliorate cognitive deficits in AD,potentially due to its ability to modulate single or nested brain rhythms,local or distant synchronization,and metabolic activity,which can influence cognitive functions.This review summarizes the research progress of tACS in the treatment of AD,aiming to provide new insights into the exploration of the pathogenesis and treatment of AD.

Objective:To summarize the clinical, imaging, and pathological characteristics of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes syndrome (MELAS) to improve the diagnosis of this rare disease.Methods:A retrospective case series was conducted to collect the clinical data and results of genetic testing, muscle biopsy, and imaging studies including computed tomography (CT), magnetic resonance imaging (MRI), and magnetic resonance spectroscopy (MRS) of 35 patients with MELAS admitted to the Nanjing Drum Tower Hospital from 2012 to 2021. Descriptive statistical analysis including mean, standard deviation, and frequency percentage were carried out.Results:The average age of onset of the patients was 30.2±2.3 years; the prevalence of family history was 20%. The two main initial symptoms were limb weakness and convulsions. The clinical manifestations of the neuromuscular system were proximal muscle weakness and exercise intolerance. The endocrine system is the most affected outside the neuromuscular system, with diabetes being the most common condition. Among the five patients who underwent brain CT, four showed hypodense lesions and two had calcified lesions. Brain MRI in 26 patients showed that the lesions more often affected the parietal lobe, basal ganglia, temporal lobe, occipital lobe, and frontal lobe than the infratentorial areas. Twelve of these individuals exhibited different levels of brain atrophy. Among the 10 patients who underwent 1H-MRS, nine showed a decrease in N-acetylaspartate (NAA) levels, eight exhibited abnormal lactate elevation (Lac peaks), whereas six had both reduced NAA levels and the presence of Lac peaks. Thirty-one patients underwent genetic testing; among them, 25 were found to have the mt.3243A>G mutation, while the remaining six exhibited rare gene alterations. Muscle biopsies were performed in 21 patients, and 15 showed abnormal mitochondrial proliferation manifested by ragged red fibers and defective oxidative phosphorylation manifested by cytochrome C oxidase (COX) enzyme-deficient muscle fibers. Conclusion:The clinical manifestations of MELAS syndrome are variable and complex, and early atypical symptoms could be missed or misdiagnosed. A detailed clinical history, imaging MRS analysis, muscle biopsy, and genetic testing are necessary to confirm the accurate diagnosis of MELAS.