Cortical plasticity following intramuscular lidocaine injection

Abstract

ABSTRACT BACKGROUND AND OBJECTIVES: The manipulation of peripheral neuronal activity can alter the excitability of the primary motor cortex; however, it is not known whether this occurs after intramuscular injections of lidocaine. Therefore, the investigation focused on neurophysiological changes, assessed with transcranial magnetic stimulation, after lidocaine (0.5mL, 2%) injection in the first dorsal interosseous muscle of the dominant hand of healthy individuals. METHODS: Exploratory, double-blind, parallel laboratory study. Twenty-eight healthy subjects (mean age: 29.6 years, 15 women). Measurements with transcranial magnetic stimulation included resting motor threshold, motor evoked potential, intracortical facilitation, and short intracortical inhibition. Lidocaine injection (LID group) was compared to dry needling (DRY group), saline injection (SAL group), and no intervention (CTL group). Participants were randomly placed in each group. Muscle strength and measures of peripheral excitability (rheobase and chronaxie) were also evaluated to detect whether the interventions generated changes in the peripheral neuromuscular excitability. Evaluations were performed over four time points: immediately before and after intervention and 30 and 60 minutes after intervention. RESULTS: A generalized linear model was used to identify differences between the LID, DRY, and SAL groups and the CTL group. The results showed that motor evoked potentials were modified in the LID group (p<0.005). CONCLUSION: The injection of lidocaine into the first dorsal interosseous muscle in the dominant hand of healthy adults alters motor evoked potentials.