rTMS modulates reciprocal inhibition in patients with traumatic spinal cord injury

Abstract

Study design: Randomized, double-blind, crossover, sham-controlled trial. Objectives: Repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) leads to a significant reduction of spasticity in subjects with spinal cord injury (SCI), but the physiological basis of this effect is still not well understood. The purpose of this study was to evaluate the disynaptic reciprocal Ia inhibition of soleus motoneurons in SCI patients. Setting: Department of Neurology, Merano, Italy and TMS Laboratory, Paracelsus Medical University, Salzburg, Austria. Methods: Nine subjects with incomplete cervical or thoracic SCI received 5 days of daily sessions of real or sham rTMS applied over the contralateral M1. We compared the reciprocal inhibition, the Modified Ashworth Scale and the Spinal Cord Injury Assessment Tool for Spasticity at baseline, after the last session and 1 week later in the real rTMS and sham stimulation groups. Results: We found that real rTMS significantly reduced lower limb spasticity and restored the impaired excitability in the disynaptic reciprocal inhibitory pathway. Conclusions: In a small proof-of-concept study, rTMS strengthened descending projections between the motor cortex and inhibitory spinal interneuronal circuits. This reversed a defect in reciprocal inhibition after SCI, and reduced leg spasticity.

The effects of anodal transcranial direct current stimulation and patterned electrical stimulation on spinal inhibitory interneurons and motor function in patients with spinal cord injury

“…Another widely used noninvasive brain stimulation technique called repetitive transcranial magnetic stimulation (rTMS) was shown to reduce lower limb spasticity (Kumru et al 2010 ), and restore impaired excitability in disynaptic reciprocal inhibition in subjects with SCI (Nardone et al 2014 ). These reports support our hypothesis that increasing the excitability of the primary motor cortex using the modulation technique, such as anodal tDCS and high frequency rTMS, will increase descending input from the primary motor cortex to spinal inhibitory interneurons, which would then increase changes in disynaptic reciprocal inhibition and thus, improve ankle movement in patients with incomplete SCI.…”

Effects of high-frequency transcranial magnetic stimulation on functional performance in individuals with incomplete spinal cord injury: study protocol for a randomized controlled trial

“…Many studies have used rTMS as a non-invasive and painless method to induce long-lasting changes in the excitability of cortical and corticospinal pathways after iSCI. In this scenario, rTMS has been found effective in enhancing corticospinal synaptic transmission [ 12 ], reducing spasticity [ 13 , 14 , 23 ] and improving sensorimotor function after iSCI [ 14 – 16 ], although we note none of these studies reported associated effect sizes in their analyses. However, other studies report less positive findings, including unchanged sensorimotor function [ 24 ], as well as unaltered cortical excitability and level of spasticity [ 16 ] in response to rTMS.…”

“…Indeed, studies indicate that motor improvements may be due to modification of corticospinal projections by increasing motor cortical excitability [ 14 – 16 ] and, consequently, promote plasticity associated with functional recovery [ 22 ]. Additionally, reduction in spasticity may occur through enhancement of descending corticospinal projections and segmental effects on spinal interneurons that might strengthen inhibitory connections [ 13 , 14 , 23 ].…”

Effects of intermittent theta burst stimulation on spasticity after spinal cord injury

“…Increasing the excitability of the M1 would modify descending corticospinal influences and increase inhibitory input, which would then reduce segmental spinal excitability and thus reduce limb spasticity in patients with incomplete SCI. rTMS might strengthen descending projections between the motor cortex and inhibitory spinal interneuronal circuits, thus reducing leg spasticity (Nardone et al, 2014).…”

“…It has been shown that high-frequency (HF) rTMS induced significant reduction in the spasticity in the lower extremities in incomplete SCI (Kumru et al, 2010;Nardone et al, 2014). In the first study 20 Hz rTMS was applied on the vertex for 5 days (Kumru et al, 2010).…”