Epidural stimulation after SCI promotes standing ability
MedWire News: Epidural stimulation of the lumbosacral spinal cord allowed a patient with spinal cord injury (SCI) to stand, with assistance for balance but supporting his own weight, a case study shows.
In addition, investigators also observed locomotor-like patterns when various stimulation patterns were optimized for stepping.
"Task-specific training with epidural stimulation might reactivate previously silent spared neural circuits or promote plasticity," suggest Reggie Edgerton (University of California, Los Angeles, USA) and colleagues in The Lancet.
Past animal models have shown that the spinal cord can produce locomotor output without input from the brain through central pattern recognition.
Cats with complete transection of the spinal cord, for example, are able to stand and step when sensory input is provided to the lumbosacral circuitry, report the authors.
With this in mind, the researchers hypothesized that stimulating the lumbosacral spinal cord epidurally, in addition to intense training, could allow patients with a complete SCI to stand and step.
A 23-year-old man with paraplegia from a C7-T1 subluxation caused by a motor vehicle accident in 2006 underwent 170 locomotor training sessions for 26 months. At baseline, the patient's neurological deficit was grade B as assessed by the American Spinal Injury Association impairment scale.
After training, a 16-electrode array was surgically inserted on the L1-S1 cord segments of the dura in December 2009. Stimulation of the spinal cord was done in sessions lasting 250 minutes.
Over the course of nearly 30 experiments, using various combinations of stimulation to obtain optimum efferent patterns, the epidural stimulation allowed the patient to stand with assistance for balance for 4 minutes and 15 seconds.
The researchers point out that epidural stimulation induced standing by "stimulating afferent fibres in the dorsal root and engaging populations of interneurons that integrated load-bearing-related proprioceptive input to coordinate motor pool activity."
The patient also "managed robust, consistent, rhythmic stepping-like activity" during manually facilitated stepping when tonic epidural stimulation and stepping-associated proprioception was present.
"This case study supports the proof of principle that human beings have conserved spinal locomotor circuitry, as found in other mammals," conclude Edgerton and colleagues.
Interventions such as this could be a viable clinical approach for functional recovery after severe paralysis, they add. However, they urge caution in generalizing the findings, given the case-study nature of the report.
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