Repetitive Transcranial Magnetic Stimulation in Individuals With Spinal Cord Injury: A Pilot Study
Condition: Spinal Cord Injury
MeSH terms: Spinal Cord Injuries; Wounds and Injuries
Study type: Interventional

Summary: 
      This study will investigate how repetitive transcranial magnetic stimulation delivered as a
      protocol called 'continuous theta-burst stimulation (cTBS)' alters motor output and force
      control to a muscle in the forearm and touch perception in individuals with chronic,
      incomplete spinal cord injury. CTBS is a non-invasive technique that involved repetitive
      delivery of transcranial magnetic stimulation at a frequency of 30 Hz over the arm
      representation in the primary motor or sensory cortex. The purpose of this study is to
      determine whether cTBS is an effective intervention to increase motor output to a muscle and
      increase force control of that muscle and also improve the sense of touch.
    

Detailed description: 
      Experience and injury-induced neuroplasticity occur in sensory and motor pathways and
      cortices. Sensory and motor cortices are interconnected and collectively allow for the
      execution of fine, skilled hand control. Of particular interest is the role of somatosensory
      cortex in modulating the neural activity within primary motor cortex and ultimately
      influencing the control of hand movement. For somatosensory cortex to be effective in guiding
      hand movement it must receive an uninterrupted stream of somatosensory afferent input from
      skin, muscle and tendons that are active during hand movement. Damage to afferent input
      pathways compromise the integrity of necessary somatosensory input and contribute to impaired
      motor control of the hand. Following an incomplete spinal cord injury (SCI), damage to the
      somatosensory and motor pathways are widespread thereby compromise the integrity of afferent
      input that reaches somatosensory cortex [1,2]. Reducing the afferent input to somatosensory
      cortex leads to local changes in the concentration of GABA and promotes sensorimotor
      reorganization [3].

      Transcranial magnetic stimulation has been used in SCI to measure residual corticospinal
      function [4], determine changes in the excitability of neural circuitry within the primary
      motor cortex [5] and induce short-lasting changes in the excitability of spinal motor neurons
      [6]. To date, TMS research in SCI has primarily focused on lower limb function, likely fueled
      by the desire to promote functional recovery of locomotion and balance control. However, one
      of the main determinants in promoting independent living is the ability to feed and groom
      oneself, relying primarily on the control of the upper limb and the dexterous use of the
      hand. The proposed research will investigate the ability to increase motor output to muscle
      of the hand and upper limb through inducing short-lasting changes within SI and investigate
      whether this has functional implication in force production, motor control and touch
      perception.

      TMS may be delivered as a single, pair or a train of repetitive pulses over a particular body
      representation within the primary motor cortex or primary somatosensory cortex. One type of
      repetitive TMS is called continuous theta-burst stimulation (cTBS). The present study will
      deliver cTBS over the primary motor and primary somatosensory cortices in individual with
      chronic SCI. Measurements will be made before and following the cTBS protocol. These measures
      include 1) the amplitude of the motor evoked potential (MEP) that is evoked by single pulse
      TMS and measured in the forearm muscle, 2) force production whereby participants will be
      asked to perform a grip strength task where maximum force production will be measured and
      ability to dynamically control force production will be assessed, and 3) touch sensation
      whereby participants will partake in a temporal order judgment psychophysical task such that
      they must identify which fingertip received the tactile stimulus.
    

Intervention name(s): Transcranial magnetic stimulation
Intervention type(s): Device
Intervention description(s): Intermittent theta-burst stimulation is a form of repetitive Transcranial magnetic stimulation. ITBS is a non-invasive, non-painful procedure being used worldwide to study brain function and promote short-term changes (~1 hour) in neural activity in the brain. The delivery of cTBS requires ~ 40 seconds in total.
Other intervention name(s): Repetitive TMS; intermittent theta-burst stimulation
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: transcranial magnetic stimulation; spinal cord injury; motor cortex; somatosensory cortex