Jered Chinnock, 29, injured his spinal cord at the thoracic vertebrae in the middle of his back in a snowmobile accident in 2013. He was diagnosed with a complete loss of function below the spinal cord injury, meaning he could not move or feel anything below the middle of his torso. With an implanted spinal cord stimulator turned on, Chinnock was able to step with a front-wheeled walker while trainers provided occasional assistance.
A spinal cord stimulator. Image credit: Mayo Clinic.
In a Mayo Clinic-led study, which began in 2016, Chinnock participated in 22 weeks of physical therapy and then had an electrode surgically implanted by Mayo Clinic’s Dr. Kendall Lee and colleagues.
The implant sits in the epidural space (the outermost part of the spinal canal) at a specific location below the injured area.
The electrode connects to a pulse generator device under the skin of Chinnock’s abdomen and communicates wirelessly with an external controller.
Dr. Lee and co-authors then tried to determine if Chinnock could stand and walk with assistance.
During 113 rehabilitation sessions, the researchers adjusted stimulation settings, trainer assistance, harness support and speed of the treadmill to allow him maximum independence.
The study demonstrated that Chinnock was able to walk over ground using a front-wheeled walker and step on a treadmill placing his arms on support bars to help with balance. However, when stimulation was off, Chinnock remained paralyzed.
In the first week, Chinnock used a harness to lower his risk of falling and to provide upper body balance. Trainers were positioned at his knees and hips to help him stand, swing his legs and shift his weight.
Because Chinnock did not regain sensation, he initially used mirrors to view his legs, and trainers described leg position, movement and balance.
By week 25, he did not need a harness, and trainers offered only occasional help.
By the end of the study period, he learned to use his entire body to transfer weight, maintain balance and propel forward, requiring minimal verbal cues and periodic glances at his legs.
“What this is teaching us is that those networks of neurons below a spinal cord injury still can function after paralysis,” said Dr. Lee, director of Mayo Clinic’s Neural Engineering Laboratories.
“Now I think the real challenge starts, and that’s understanding how this happened, why it happened, and which patients will respond,” said Dr. Kristin Zhao, director of Mayo Clinic’s Assistive and Restorative Technology Laboratory.
The results are described in a paper published online this week in the journal Nature Medicine.
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Megan L. Gill et al. Neuromodulation of lumbosacral spinal networks enables independent stepping after complete paraplegia. Nature Medicine, published online September 24, 2018; doi: 10.1038/s41591-018-0175-7
