H reflex modulation by transcranial magnetic stimulation in spinal cord injury subjects after gait training with electromechanical systems

Study design: Prospective longitudinal study. Objectives: The aim of this study was to examine the effects of transcranial magnetic stimulation (TMS) on the soleus H reflex in patients with spinal cord injury (SCI) before and after locomotion training. Setting: Neurorehabilitation hospital in Barcelona, Spain. Methods: H reflex was elicited in 29 incomplete patients with SCI at 20, 50 and 80 ms after single vertex TMS, and compared with 13 healthy subjects. Patients were subdivided in two groups according to time since injury (<3 months, 3-12 months), and all received training with electromechanical systems. The H reflex modulation pattern to TMS was reassessed and the results were analyzed as a function of change in the patient clinical score. Results: Healthy subjects showed a significant H reflex facilitation at 20 ms (186.1%) and at 80 ms (190.6%) compared with the control H reflex. In patients, the H reflex facilitation at 20 ms was significantly reduced before training (142.5%, P = 0.039) compared with healthy subjects. After training, patients with <3 months exhibited an increase in H reflex facilitation at 20 ms (170.7%, P = 0.04), a greater gait velocity (P = 0.014) and a positive correlation with the walking index for spinal cord injury (WISCI II) scale (P = 0.050), compared with those with >3 months. Conclusions: TMS-induced H reflex modulation may help in the assessment of changes in the descending control of leg reflexes. Our results suggest that the changes on reflex modulation in patients with SCI occur within the first 3 months after injury. Spinal Cord (2010) 48, 400-406; doi:10.1038/sc.2009.151; published online 24 November 2009