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Mitochondrial myopathy encephalopathy lactic acidosis and stroke-like episodes (MELAS) is an important cause of stroke-mimicking diseases that predominantly affect patients before 40 years of age. MELAS results from gene mutations in either mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) responsible for the wide spectrum of clinical symptoms and imaging findings. Neurological manifestations can present with stroke-like episodes (the cardinal features of MELAS), epilepsy, cognitive and mental disorders, or recurrent headaches. Magnetic resonance imaging (MRI) is an important tool for detecting stroke-like lesions, accurate recognition of imaging findings is important in guiding clinical decision making in MELAS patients. With the development of neuroimaging technologies, MRI plays an increasingly important role in course monitoring and efficacy assessment of the disease. In this article, we provide an overview of the neuroimaging features and the application of novel MRI techniques in MELAS syndrome.

Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a rare mixed neuronal-glial tumor of central nervous system. Chromosome microarray usually identifies co-deletion of the short arm of chromosome 1 and the long arm of chromosome 19 as well as fusion of the KIAA1549 and BRAF genes.We describe a case of a 3-year-old boy with typical imaging and histopathological features, but without KIAA1549-BRAF fusion and 1p deletion. Additionally, a literature review is performed summarizing the clinical features, management, and prognosis of this rare entity.A 3-year-old boy presented with chronic headache and vomiting. On initial MRI scanning, diffuse thickening with enhancement of the cerebral and spinal leptomeninges could be detected after contrast injection. Multiple cystic lesions were found located on infratentorial leptomeninges, with progressive thickening of leptomeninges and increasing cysts on follow-up MRI after 9 months. Meningeal biopsy was carried out, showing that most of tumor cells were composed of oligodendroglioma-like cells. The tumor cells were immunopositive for GFAP, Olig-2, and synaptophysin but negative for IDH-1 and H3k27M. Molecular genetic testing did not detect KIAA1549-BRAF fusion, 1p deletion, or 1p/19q co-deletion. The patient was finally diagnosed as DLGNT after multidisciplinary team consultation.Given that the clinical and pathological mechanism of DLGNTs remains unclear, our case gives supplement about the diversity of molecular genetic characteristics. Combination of clinical, neuroradiological, and histopathological data is particularly important for the diagnosis of DLGNTs, till now.

Objective: This meta-analysis was carried out for assessing the accuracy of intravoxel incoherent motion (IVIM) parameters true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f) in differentiating low-grade gliomas (LGGs) from high-grade gliomas (HGGs). Methods: Literatures concerning IVIM in the grading of brain gliomas published prior to October 20, 2020, searched in the Embase, PubMed, and Cochrane library. Use the quality assessment of diagnostic accuracy studies 2 (QUADAS 2) to evaluate the quality of studies. We estimated the pooled sensitivity, specificity, and the area under the summary ROC (SROC) curve to identification the accuracy of IVIM parameters D, D*, and f evaluation in grading gliomas. Results: Totally, 6 articles including 252 brain gliomas conform to the inclusion criteria. The pooled sensitivity of parameters D, D*, and f derived from IVIM were 0.85 (95%Cl, 0.76–0.91), 0.78 (95%Cl, 0.71–0.85), and 0.89 (95%Cl, 0.76–0.96), respectively. The pooled specificity were 0.78 (95%Cl, 0.60–0.90), 0.68 (95%Cl, 0.56–0.79), and 0.88 (95%Cl, 0.76–0.94), respectively. Meanwhile, the AUC of SROC curve were 0.89 (95%Cl, 0.86–0.92) , 0.81 (95%Cl, 0.77–0.84), and 0.94 (95%Cl, 0.92–0.96), respectively. Conclusion: This meta-analysis suggested that IVIM parameters D, D*, and f have moderate or high diagnosis value accuracy in differentiating HGGs from LGGs, and the parameter f has greater sensitivity and specificity. Standardized methodology is warranted to guide the use of this method for clinical decision-making. However, more clinical studies are needed to prove our view. Advances in knowledge: IVIM parameter f showed greater sensitivity and specificity, as well as excellent performance than parameter D* and D.

In this research, we report the results of experimental and density functional theory (DFT)/time-dependent DFT analyses of two new azo derivatives that absorb light in the visible range: (E)-2-((4-(diethylamino)phenyl)diazenyl)-6-methoxy-3-methylbenzo[d]thiazol-3-ium (I) and N,N-diethyl-4-((6-methoxybenzo[d]thiazol-2-yl)diazenyl)aniline (II) in the presence of water (I) and chloroform (II). The molecular geometry and excited states of the compounds were investigated, and their natural bond orbital, frontier molecular orbital, quantum theory of atoms in molecules, and nonlinear optical (NLO) parameters were calculated. In addition, Fourier-transform infrared, nuclear magnetic resonance, and ultraviolet/visible spectral parameters were generated from the derived structures and compared to experimental spectral parameters. The practical applicability of the azo derivatives was investigated by determining their electronic and NLO properties, which demonstrated that both molecules have potential for optoelectronic and photonic applications. A high degree of approximation between the calculated and experimental results was demonstrated.