rTMS Protocol Effects on Respiratory Neuroplasticity
rTMS is a noninvasive procedure that uses magnetic fields to stimulate nerve cells in the brain.
High spinal cord injuries (SCIs) lead to permanent diaphragmatic paralysis. The search for therapeutics to induce functional motor recovery is essential.
One promising noninvasive therapeutic tool that could harness plasticity in a spared descending respiratory circuit is repetitive transcranial magnetic stimulation.
Here, we tested the effect of chronic high-frequency rTMS above the cortical areas in rats when applied for 7 days, 1 month, 2 months.
An increase in intact hemidiaphragm electromyogram (EMG) activity and excitability was observed after 1 month of rTMS application.
Interestingly, despite no real functional effects of rTMS treatment on the injured hemidiaphragm activity during eupnea, 2 months of rTMS treatment strengthened the existing crossed phrenic pathways, allowing the injured hemidiaphragm to increase its activity during the respiratory challenge (i.e., asphyxia).
This effect could be explained by a strengthening of respiratory descending fibers in the ventrolateral funiculi, sustained by a reduction in inflammation in the C1–C3 spinal cord, and acceleration of intracellular plasticity processes in phrenic motoneurons after this chronic treatment.
These results suggest that chronic high-frequency rTMS can ameliorate respiratory dysfunction.
It also elicit neuronal plasticity with the reduction of post-traumatic inflammatory processes in the cervical spinal cord.
This therapeutic tool could be used and combined with other therapeutic interventions in order to enhance beneficial outcomes.