F44. Clinical characters and repetitive nerve stimulation features of Musk-MG

Abstract

Introduction To analyze clinical characters and low frequency repetitive nerve stimulation (LF-RNS) features of Musk-MG. Methods A case-controlled retrospective analysis of 9 cases of Musk-MG and 19 cases of AchR-MG. Results There was no significant difference between the two groups in gender and age of onset. Musk-MG groups showed (1) the course of disease was prolonged obviously (1.80 yrs vs 0.62 yr, p = 0.033), the location of onset were extraocular muscles (2/9), bulbar muscle (3/9), neck (3/9), and AchR-MG (within the main parts in the extraocular muscles of 12/19) had significant difference ( p = 0.041); Neostigmine test showed that the positive rate (3/9) was significantly lower than that in group Musk-MG (16/19, p = 0.010). In the MGFA classification, IIa + IIIa accounted for 5 cases (5/9), while AchRab-MG accounted for 14 cases of 14/19, there was a significant difference ( p = 0.039). (2) The total positive rate of low frequency RNS was significantly lower than that of (7/9) AchR-MG group (19/19, p = 0.033). The positive rate of RNS of orbicularis oculi muscle had no obvious difference in the two groups (6/9, vs 13/19, p = 0.733 RNS), trapezius muscle (5/9) was lower than that of group AchR-MG (18/19, p = 0.011), abductor digiti minimi (0/9) RNS was lower than that of group AchR-MG (7/19, p = 0.000). (3) In Musk-MG group, the positive rate of RNS in orbicularis oculi (66.7%) > trapezius muscle RNS positive rate (55.6%) > abductor hallucis muscle (0%), while in AchR-MG group, the positive rate of trapezius muscle RNS (94.7%) > the positive rate of orbicularis oculi muscle RNS (68.4%) > the RNS positive rate of little finger abductor muscle (36.8%). Conclusion Compared with AchR-MG, Musk-MG showed more bulbar onset, lower positive rate of neostigmine test, longer diagnosis time, lower positive rate of low frequency RNS, lower positive rate of RNS of trapezius muscle and abductor digit muscle.