Modulation of spinal cord excitability by subthreshold repetitive transcranial magnetic stimulation of the primary motor cortex in humans

• Published in: Neuroreport Vol. 12; no. 17; p. 3845
• Main Authors: Valero-Cabré, A, Oliveri, M, Gangitano, M, Pascual-Leone, A
• Format: Journal Article
• Language: English
• Published: England 04.12.2001
• Subjects: Adult; Electric Stimulation Therapy - methods; Electromyography; Humans; Male; Membrane Potentials - physiology; Motor Cortex - physiology; Movement Disorders - physiopathology; Movement Disorders - therapy; Muscle Contraction - physiology; Muscle Spasticity - physiopathology; Muscle Spasticity - therapy; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Neural Conduction - physiology; Neurons - physiology; Pyramidal Tracts - physiology; Reaction Time - physiology; Reflex, Monosynaptic - physiology; Spinal Cord - physiology; Transcranial Magnetic Stimulation
• ISSN: 0959-4965
• DOI: 10.1097/00001756-200112040-00048

Repetitive transcranial magnetic stimulation (rTMS) allows the modulation of intra-cortical excitability and may therefore affect the descending control of spinal excitability. We applied rTMS at subthreshold intensity and 1 Hz frequency for 10 min to the left primary motor cortex representation of the flexor carpi radialis muscle (FCR) in 10 subjects and assessed the H and M responses to median nerve stimulation before and after the rTMS. Following rTMS, H wave thresholds significantly reduced by approximately 20%. Maximal H but not M wave amplitude significantly increased over the baseline, so that H/M amplitude ratio was increased by 41%. Sham stimulation did not induce any noticeable change in M or H waves. Slow rTMS might facilitate monosynaptic spinal cord reflexes by inhibiting the cortico-spinal projections modulating spinal excitability.