Like in adults, children with spinal cord injury (SCI) in children suffer from
neuromuscular paralysis which results in the inability to sit, stand, and walk. Current
therapeutic interventions, e.g. leg braces, wheelchairs, largely aim to compensate for
paralysis based on the assumption that damage to the central nervous system is permanent
and irreversible.The discovery of the "intelligent" spinal cord, known as the central
pattern generator (CPG), has demonstrated that complex neuronal networks are capable of
generating rhythmic and coordinated motor patterns and has set forth a major paradigm
shift in the investigators expectation of the possibility for recovery even with severe
SCI. Studies have demonstrated, first, that after SCI, the CPG can be "accessed",
reactivated, and retrained via sensory feedback arising from the muscles and joints
during activity-based locomotor training (AB-LT). Second, application of epidural and
transcutaneous stimulation (TcStim) to the spinal cord below the level of lesion can
augment the neuromuscular capacity for voluntary movement, standing and stepping in
adults with chronic motor complete SCI. While neural mechanisms for stepping regulation
have been demonstrated in adults testing single vs. multi-site stimulation, this inherent
capacity must be examined in children with SCI. Similarly, the addition of stimulation
during AB-LT in adults with motor complete SCI has resulted in remarkable recovery of
over ground walking. The immediate and long-term response of such combined therapeutic
exposure and subsequent training has yet to be examined in children. Children with SCI
may not only benefit from these novel therapeutic approaches but also demonstrate greater
improvements in neuromuscular recovery due to inherent plasticity. The investigators'
preliminary work has demonstrated the safety and feasibility of TcStim in children with
SCI. Therefore, the specific aims of this proposal are to 1) investigate the spinal
mechanisms for regulation of locomotor circuitry in children with SCI using TcStim, 2)
assess whether the combination of task-specific AB-LT and TcStim can acutely potentiate
lower limb muscle activity during facilitated stepping, and 3) assess training effects of
TcStim combined with AB-LT to promote stepping capacity in non-ambulatory children with
SCI.
For this pilot study 8 participants, ages 4-12 years with chronic, acquired SCI, T10 and
above and non-ambulatory will be recruited.
For Aim 1, n=8, TcStim will be used to stimulate a single or multi site spinal levels to
produce stepping/locomotor activity in lower limbs. Knee, hip, ankle kinematics and
electromyography (EMG) of the lower limb muscles in response to stimulation will be
recorded during the experiments. The investigators will determine the stimulation
parameters that produce rhythmic movements with the greatest increase in lower limb joint
excursions as well as EMG amplitude.
For Aim 2, n=8, TcStim will be delivered while participants attempt to take a step
overground and while stepping on a computerized treadmill with an overhead partial body
weight support (BWS) system. The participants will be stepped at age-appropriate speeds
and BWS optimizing the stepping kinematics. The speed and the amount of body weight
support provided during the assessment as well as full body kinematics and EMG signals
from trunk and lower limb muscles will be recorded during facilitated stepping with and
without TcStim.
For Aim 3, n=6, participants will receive 60 sessions of AB-LT+Tcstim. Ability to
initiate and complete a step overground with and without stimulation along with full body
kinematics and electromyographic (EMG) signals from trunk and lower limb muscles will be
recorded at baseline, 20, 40, and 60 sessions of the combined therapy of AB-LT plus
TcStim.