Objective To research the pathogeny and the electromyographic characteristics of myokymia.Methods The clinical features and electromyography of 42 elderly patients with myokymia were examined. Results Symptomatic myokymia (SM) in 27 cases was caused by low salt syndrome, thyrotoxemia, urinaemia, chronic wasting diseases (such as carcinoma of the stomach or liver), brachial plexus neuropathy, lead poisoning, chronic inflammatory demyelinating polyradiculoneuritis, succinylcholine narcosis, restless leg syndrome or Isaac's syndrome.Symptomatic facial myokymia was caused by neoplasm of the brain stem or in posterior cranial fossa, multiple sclerosis or other causes. Primary myokymia ( PM ) in 15 cases involved idiopathic generalized and benign myokymia.Compared with PM, SM was more constant and powerful. Myokymia potential appeared in the electromyograms of 42 of the patients. The majority of patients with SM had accompanying myotonic discharge. Conclusion The pathogeny and electromyographic characteristics of symptomatic myokymia are different from the primary stage.

Objective:To investigate the biological behavior spectrum of platelet-derived growth factor alpha receptor (PDGFRA)-mutant gastrointestinal stromal tumor (GIST), and to compare the clinical values of the Zhongshan method of benign and malignant evaluation with the modified National Institutes of Health (NIH) risk stratification.Methods:A total of 119 cases of GIST with PDGFRA mutation who underwent surgical resection at Zhongshan Hospital, Fudan University from 2009 to 2020 were collected. The clinicopathological data, follow-up records, and subsequent treatment were reviewed and analyzed statistically.Results:There were 79 males and 40 females. The patients ranged in age from 25 to 80 years, with a median age of 60 years. Among them, 115 patients were followed up for 1-154 months, and 13 patients progressed to disease. The 5-year disease-free survival (DFS) and overall survival (OS) were 90.1% and 94.1%, respectively. According to the modified NIH risk stratification, 8 cases, 32 cases, 38 cases, and 35 cases were very-low risk, low risk, intermediate risk, and high risk, and 5-year DFS were 100.0%, 95.6%, 94.3%, and 80.5%, respectively. There was no significant difference in prognosis among the non-high risk groups, only the difference between high risk and non-high risk groups was significant ( P=0.029). However, the 5-year OS was 100.0%, 100.0%, 95.0% and 89.0%, and there was no difference ( P=0.221). According to the benign and malignant evaluation Zhongshan method, 43 cases were non-malignant (37.4%), 56 cases were low-grade malignant (48.7%), 9 cases were moderately malignant (7.8%), and 7 cases were highly malignant (6.1%). The 5-year DFS were 100.0%, 91.7%, 77.8%, 38.1%, and the difference was significant ( P<0.001). The 5-year OS were 100.0%, 97.5%, 77.8%, 66.7%, the difference was significant ( P<0.001). Conclusions:GIST with PDGFRA gene mutation shows a broad range of biological behavior, ranging from benign to highly malignant. According to the Zhongshan method, non-malignant and low-grade malignant tumors are common, the prognosis after surgery is good, while the fewer medium-high malignant tumors showed poor prognosis after surgical resection. The overall biological behavior of this type of GIST is relatively inert, which is due to the low proportion of medium-high malignant GIST. The modified NIH risk stratification may not be effective in risk stratification for PDGFRA mutant GIST.