Clinical features of the first attack with leukodystrophy-like phenotype in children with myelin oligodendrocyte glycoprotein antibody-associated disorders.

BACKGROUND: Myelin oligodendrocyte glycoprotein antibody-associated disorders (MOGAD) is identified autoimmune disorder with a predominance in paediatric patients, and the disease spectrum has expanded with clinical and radiological patterns. The aim of the study was to describe the clinical characteristics of the first attack with leukodystrophy-like phenotype with MOGAD in children. METHODS: Patients hospitalized at the Children's Hospital of Chongqing Medical University from June 2017 to October 2021 with positive MOG antibodies and phenotype of leukodystrophy-like (symmetric white matter lesions) were retrospectively analyzed. Cell-based assays (CBAs) were used to test MOG antibodies. RESULTS: Four cases from 143 MOGAD patients were recruited, with two females and two males. The age of onset is all under 6 years old. At the last follow-up, four cases exhibited a monophasic course, including ADEM in three patients and encephalitis in one patient. The mean EDSS score at onset was 4.62 ± 2.93, and the modified Rankin score (mRS) was 3.00 ± 1.82. First-attack symptoms include fever, headache, vomiting, seizure, loss of consciousness, emotional and behavioural disorder, and ataxia. The brain MRI showed prominent extensive and essentially symmetric distribution lesions in the white matter. All patients showed clinical and partial radiological improvement after intravenous immunoglobulin and/or glucocorticoid treatment. CONCLUSION: The first attack with MOGAD onset of leukodystrophy-like phenotype was more frequently seen in younger children than other phenotype patients. The patients may show impressive neurologic disorders, but most patients who receive immunotherapy have a good prognosis.

Bending losses of trench-assisted few-mode optical fibers.

A semianalytical method based on the perturbation theory is developed to calculate the bending losses of individual modes of few-mode fibers (FMFs); it is applicable for optical fibers with arbitrary circularly symmetric index profile, especially for trench-assisted fibers. The bending performance of trench-assisted step-index FMFs and parabolic-index FMFs are investigated with three key parameters (i.e., the refractive index difference of trench-cladding, the width of the trench, and the distance of the core-trench). Then, a performance index is defined to estimate the bending performance for FMFs. It is shown that changing the distance of the trench-core, for each order of mode, there is a minimum bending loss, which can be used for fiber optimization. This optimization position (core-trench distance) decreases as the mode order increases. It is found that the bending performance of parabolic-index FMFs is better than that of step-index FMFs with fixed core radius and cutoff wavelength. The conclusions are helpful for understanding the mechanism of bending loss for FMFs, and make contributions to designing and manufacturing of few-mode bend-insensitive fibers.