眼肌型重症肌无力临床分析

目的分析眼肌型重症肌无力(OMG)的临床特点及眼部征象.方法采用回顾性研究的方法,对92例OMG、40例全身型重症肌无力(GMG)的临床资料进行统计分析.结果①OMG好发于1～24岁,17.4%有复发史,91.9%儿童重症肌无力MG表现为OMG.②OMG有95.6%表现为上睑下垂,70.5%表现为眼球活动障碍(斜视),多表现为单侧上睑下垂(57.6%),双侧上睑下垂率(38.0%)显著低于GMG(70.0%),OMG眼球垂直与水平运动障碍率分别是48.9%、43.2%,垂直与水平方向同时发生障碍者占21.6%.③OMG新斯的明试验和疲劳试验阳性率(88.0%、86.4%)与GMG相似,胸腺瘤阳性率(5.2%)、神经低频重复电刺激阳性率(23.2%)显著低于GMG.④28.6%OMG胸腺CT正常,经病理诊断为胸腺增生.结论OMG好发于青春期,病程长,易复发;表现为不对称的上睑下垂、斜视;即使胸腺CT结果正常也存在胸腺异常的可能性.     

Refractory myasthenia gravis: Characteristics of a portuguese cohort

Introduction: Some myasthenia gravis (MG) patients are refractory to conventional treatments. Methods: To describe the clinical features of refractory MG (RMG) and explore the association with human leukocyte antigen HLA-DRB1 alleles, a cohort study of 114 consecutive MG patients was performed. Patients were classified as RMG based on predefined criteria. Results: Twenty-two patients were found to have RMG (19.3%). There were no differences between non-RMG and RMG patients with respect to sex, age of onset, abnormal 3-Hz repetitive nerve stimulation, anti-acetylcholine receptor antibody positivity, thymectomy, thymoma or thymic hyperplasia, and polyautoimmunity. HLA-DRB1*03 was more frequent in the non-RMG vs. control population (P = 3 × 10⁻⁶). The HLA-DRB1*13 allele was less frequent in non-RMG patients compared with controls (P = 0.002), and less frequent in the non-RMG group compared with the RMG group (P = 0.003). Discussion: HLA-DRB1*03 was more common in non-RMG, and the HLA-DRB1*13 allele appeared to have a protective role, as reported previously in other autoimmune disorders. Muscle Nerve 60 : 188–191, 2019     

Thymectomy may not be associated with clinical improvement in MuSK myasthenia gravis

Introduction: A randomized trial demonstrated benefit from thymectomy in nonthymomatous acetylcholine receptor (AChR)-antibody positive myasthenia gravis (MG). Uncontrolled observational and histologic studies suggest thymectomy may not be efficacious in anti–muscle-specific kinase (MuSK)-MG. Methods: The therapeutic impact of thymectomy was evaluated from data collected for a multicenter, retrospective blinded review of rituximab in MuSK-MG. Results: Baseline characteristics were similar between thymectomy (n = 26) and nonthymectomy (n = 29) groups, including treatment with rituximab (42% vs. 45%). At last visit, 35% of thymectomy subjects reached the primary endpoint, a Myasthenia Gravis Foundation of America (MGFA) post-intervention status (PIS) score of minimal manifestations (MM) or better, compared with 55% of controls (P = 0.17). After controlling for age at onset of MG, rituximab, prednisone, and intravenous immunoglobulin/plasma exchange treatment, thymectomy was not associated with greater likelihood of favorable clinical outcome (odds ratio = 0.43, 95% confidence interval 0.12–1.53, P = 0.19). Discussion: Thymectomy was not associated with additional clinical improvement in this multicenter cohort of MuSK-MG patients. Muscle Nerve 59:404–410, 2019     

An unusual primary presentation of myasthenia gravis

This patient presented with progressive eating difficulties, having been originally investigated for mechanical gastroenterological problems. Fruitless examinations led to referral to a tertiary oral medicine unit and a detailed review of his history, where the significance of progressive fatiguability during and after mastication became apparent in his dysphagia.The insidious onset contrasted with his more rapid decline in function between the initial examination and specialist electromyographic investigations, neurological admission and management. The dangers of fatigue and pharyngeal incompetence are of particular relevance to oral and maxillofacial clinicians.     

Effect of local cooling on excitation-contraction coupling in myasthenic muscle: Another mechanism of ice-pack test in myasthenia gravis

Objective

The ice-pack test is a convenient diagnostic testing procedure for myasthenia gravis (MG). We investigated the underlying mechanism of the ice-pack test performed on bilateral masseters.

Assessing neuromuscular junction stability from stimulated EMG in children

Objective

We present our 9-year experience of stimulated EMG potential analysis using concentric electrodes (SPACE) to evaluate neuromuscular junction (NMJ) disorders in awake children. The technique uses high frequency filtration of stimulated motor unit potentials and applies peak detection software to estimate mean consecutive difference (MCD).

Neuromuscular junctional disorders

Absract  Neuromuscular junctional disorders (NMJ) in children are distinct entity. They may be acquired or hereditary. They pose problem in diagnosis because of the higher occurrence of sero negative Myasthenia Gravis (MG) cases in children. The identity of MusK antibody positivity in a good percentage of sero negative cases further adds to problems in diagnosis. The Congenital Myasthenic Syndrome (CMS) which are rare disorders of hereditary neuromuscular transmission (NMT) has to be differentiated because immunotherapy has no benefit in this group. Molecular genetic studies of these diseases helps to identify specific type of CMS which is important as other drugs like Fluoxetine, Quinidine are found to be effective in some. In infancy, all can manifest as floppy infant syndrome. The important key to diagnosis is by detailed electrophysiological studies including repetitive nerve stimulation at slow and high rates and its response to anticholinesterases and estimation of Acetyl choline receptor antibodies. Other causes of neuromuscular transmission defects viz. snake venom poisoning and that due to drugs are discussed.