Motivation: During medical school, when I told a notable surgeon that I intended to enter neurology, he smirked while trying to suction clotted blood and then said, "If you like banging your head against a wall, then go to neurology." The implication being, of course, that neurologists have few cures. While I disagree with the surgeon's assessment of neurology, even I was surprised by a remarkable article in Lancet this year that demonstrated for the first time recovery of ability to stand after complete spinal cord motor injury. And, this experiment did not even use stem cells.
The theory driving this experiment is rooted in the observation that mammalian spinal cords can generate locomotor output even in absence of central input. The hypothesis is that if these spinal circuits can be stimulated, then people with spinal cord injury may be able to stand once more.
Paper: Harkema, S., Gerasimenko, Y., Hodes, J., et. al. "Effect of epidural stimulation of the lumbosacral spinal cord on voluntary movement, standing, and assisted stepping after motor complete paraplegia: a case study." Lancet (2011); 377: 1938-47.
Method: This case study examined a single subject: a 23 year old man who was paraplegic from C7-T1 subluxation after a motor vehicle accident in 2006. He had no contraction of trunk or leg muscles and only weak movements of hand muscles. He retained, however, light-touch and pinprick sensation in lower extremities. From 2007 to 2009, patient received 108 hours of step training and 54 hours of stand training during rehab with no clinical improvement. An epidural spinal cord stimulation unit was then placed on the patient to stimulate the lumbosacral epidural region at location T11-L1 (to control spinal cord segments L1-S1).
Results:
Standing: Epidural stimulation (15 Hz, 8V) of the L5-S1 segment along with extension of legs resulted in the patient being able to stand in sustained posture with full weight bearing for more than four minutes. Interestingly, the sustained standing posture was triggered by loading weight onto the legs. Simultaneous EMG showed coordinated contraction of both flexors and extensors. Of note, during standing, spontaneous postural changes occurred in response to shifts in center of gravity sagitally.
Walking: Epidural stimulation at 30-40 Hz and sensory cues (such as manually positioned stepping posture) generated walking-like motor patterns. Without stimulation, manual positioning elicited no motor response.
Function Recovery: After 80 training sessions with epidural simulation over seven months, patient recovered voluntary movement of toe extension and ankle and leg stimulation while receiving spinal stimulation. During epidural stimulation, patient also recovered bladder function with minimal post void residuals. He also recovered function of other autonomic nervous system processes and gained weight by 18%.
Discussion: This paper is not only a potential paradigm changing case report in the field of spinal cord injury but also illustrates concepts that affect our understanding of the nervous system. First, traditionally in our mind's eye, we view the sensory system and motor system as fairly indpendent pieces - one traveling up the dorsal part of the spinal cord and the other descending down the ventral part. This paper shows that for basic tasks like standing, integration of sensory input and motor output occurs at multiple levels beginning with the spinal cord. So, while evaluating patients with gait difficulty, sensory deficits must be considered along with weakness. Secondly, this paper extends the trend in our understanding that complex motions like walking occur as a result of interactions between multiple centers in the nervous system. Clearly, part of the coordination process occur in the spinal cord itself. Encouragingly, this distributive process may help us recover from seemingly "irremediable" defects such as complete motor spinal cord injury with the help of prosthetic electrical devices.
While encouraging, this paper obviously has many limitations. Before epidural stimulation becomes the next glamorous procedure, this finding has to be replicated in more than the one case report. Also, the patient in this case report is a healthy man in his 20s who had an accident. It is unclear how this result generalizes to older nervous systems of patients in their 70s. Nonetheless, for the final post of the year, this paper shows how seemingly impossible medical advances keep happening.
The theory driving this experiment is rooted in the observation that mammalian spinal cords can generate locomotor output even in absence of central input. The hypothesis is that if these spinal circuits can be stimulated, then people with spinal cord injury may be able to stand once more.
Paper: Harkema, S., Gerasimenko, Y., Hodes, J., et. al. "Effect of epidural stimulation of the lumbosacral spinal cord on voluntary movement, standing, and assisted stepping after motor complete paraplegia: a case study." Lancet (2011); 377: 1938-47.
Method: This case study examined a single subject: a 23 year old man who was paraplegic from C7-T1 subluxation after a motor vehicle accident in 2006. He had no contraction of trunk or leg muscles and only weak movements of hand muscles. He retained, however, light-touch and pinprick sensation in lower extremities. From 2007 to 2009, patient received 108 hours of step training and 54 hours of stand training during rehab with no clinical improvement. An epidural spinal cord stimulation unit was then placed on the patient to stimulate the lumbosacral epidural region at location T11-L1 (to control spinal cord segments L1-S1).
Results:
Standing: Epidural stimulation (15 Hz, 8V) of the L5-S1 segment along with extension of legs resulted in the patient being able to stand in sustained posture with full weight bearing for more than four minutes. Interestingly, the sustained standing posture was triggered by loading weight onto the legs. Simultaneous EMG showed coordinated contraction of both flexors and extensors. Of note, during standing, spontaneous postural changes occurred in response to shifts in center of gravity sagitally.
Walking: Epidural stimulation at 30-40 Hz and sensory cues (such as manually positioned stepping posture) generated walking-like motor patterns. Without stimulation, manual positioning elicited no motor response.
Function Recovery: After 80 training sessions with epidural simulation over seven months, patient recovered voluntary movement of toe extension and ankle and leg stimulation while receiving spinal stimulation. During epidural stimulation, patient also recovered bladder function with minimal post void residuals. He also recovered function of other autonomic nervous system processes and gained weight by 18%.
Discussion: This paper is not only a potential paradigm changing case report in the field of spinal cord injury but also illustrates concepts that affect our understanding of the nervous system. First, traditionally in our mind's eye, we view the sensory system and motor system as fairly indpendent pieces - one traveling up the dorsal part of the spinal cord and the other descending down the ventral part. This paper shows that for basic tasks like standing, integration of sensory input and motor output occurs at multiple levels beginning with the spinal cord. So, while evaluating patients with gait difficulty, sensory deficits must be considered along with weakness. Secondly, this paper extends the trend in our understanding that complex motions like walking occur as a result of interactions between multiple centers in the nervous system. Clearly, part of the coordination process occur in the spinal cord itself. Encouragingly, this distributive process may help us recover from seemingly "irremediable" defects such as complete motor spinal cord injury with the help of prosthetic electrical devices.
While encouraging, this paper obviously has many limitations. Before epidural stimulation becomes the next glamorous procedure, this finding has to be replicated in more than the one case report. Also, the patient in this case report is a healthy man in his 20s who had an accident. It is unclear how this result generalizes to older nervous systems of patients in their 70s. Nonetheless, for the final post of the year, this paper shows how seemingly impossible medical advances keep happening.
I have known people who have had spinal injuries and have worked to get the help needed to live fully functioning lives. One person I know got a lot of help from the pain by using spinal cord stimulation. Others worked for years to rebuild the muscles
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