Effect Of Botulinum Toxin On Biceps Brachii Spasm After Stroke By Using Strength-Duration Curve And Surface Electromyogram:A Observation Trial

Objective: This experiment was designed to verify whether the indexes of strength-duration curve(S-D curve)and surface electromyography(s EMG)of biceps brachii in spastic state because of stroke changed significantly before and after treatment with botulinum toxin,and to explore the feasibility of evaluating the effect of botulinum toxin on spasticity by S-D curve and s EMG.Methods: This experiment was an observational experiment.The modified Ashworth scale(MAS),strength-duration curve(S-D curve)and surface electromyography(s EMG)were used to evaluate the biceps brachii muscle of the subjects before,2 weeks after and 4 weeks after botulinum toxin injection.The MAS,rheobase and chronaxy of the S-D curve and mean square root when the biceps brachii was resting(RMSavg rest)and at maximum isometric contraction(RMSavg contraction)were compared,as well as the effect of injection dose on the difference of these indicators.Results: Compared with baseline,the MAS of biceps brachii at 2 weeks and 4 weeks after injection showed significant decline(P < 0.025),the rheobase(Rb)of biceps brachii at 2 weeks and 4 weeks after injection showed significant increase(P < 0.025)and the RMSavg contraction of biceps brachii at 2 weeks and 4 weeks after injection showed significant decline(P < 0.025).RMSavg rest of biceps brachii at 2 weeks after injection showed significant decline(P < 0.025),while at 4 weeks after injection did not show significant difference(P >0.025).The chronaxy(C)of biceps brachii at 2 weeks and 4 weeks after injection had no significant difference(P > 0.025).Rb was positively correlated with injection dose at 2 weeks after injection.The regression coefficient b was 0.015(P < 0.05),and the determination coefficient R2 was 0.242.Rb at 4 weeks after injection was positively correlated with injection dose as well,the regression coefficient b was 0.013(P < 0.05),and the determination coefficient R2 was 0.245.RMSavg rest was negatively correlated with injection dose at rest 2 weeks after injection.The regression coefficient b was-0.023(P < 0.05),and the determination coefficient R2 was 0.461.RMSavg rest was negatively correlated with injection dose at rest 4 weeks after injection.The regression coefficient b was-0.027(P < 0.05),and the determination coefficient R2 was 0.290.Conclusion: The rheobase(Rb)of biceps brachii muscle increased after botulinum toxin injection,and the greater the injection dose,the greater the change of rheobase;the RMSavg rest of biceps brachii muscle decreased after botulinum toxin injection,and the greater the injection dose,the greater the change of RMSavg rest.Consequently,rheobase can objectively evaluate the change of tension of biceps brachii in spastic state because of stroke after botulinum toxin injection,and the difference of Rb has a positive correlation with injection dose;RMSavg rest can objectively evaluate the change of tension of biceps brachii in spastic state after botulinum toxin injection,and the difference of RMSavg rest has a negative correlation with injection dose.