Risk-benefit value of upper extremity function by an implanted electrical stimulation device targeting chronic cervical spinal cord injury.

Study design: A cross-sectional stated-preference survey using direct-assessment questions. Objective: To determine the relative value placed on different outcomes to be used in a pivotal trial for the upper extremity configuration of the Networked Neuroprosthesis (NNP) as well as the tolerance of the expected adverse event profile. Setting: Academic medical center in the United States. Methods: Distribution of an online survey to adults living with tetraplegia; extent of agreement with each question/statement was obtaining using a 1-7 Likert scale. Results: There were 8 statements about potential benefits in arm/hand function; for all statements, more than 70% of participants rated the functions as "1-very important" to regain. There were variable degrees of concern related to risks that could occur during the 30-day post-surgical period and increasing degrees of concern related to risks that could occur in the first 5 years, potentially due to the device, based on the increasing degree of invasiveness of the intervention required to address the event. When analysing the results based on all degrees of interest, more than 64% of responders were interested in getting the NNP with a success rate threshold as low as 50% regardless of time post-injury. Chi-squared analyses revealed some associations between responses and sex, injury level, and injury duration; however, none of these were statistically significant upon post-hoc analysis. Conclusion: Data here indicate that people with tetraplegia are highly interested in a range of arm/hand functions and are tolerant of expected risks that may be associated with implanted neuroprosthetics. Sponsorship: The Institute for Functional Restoration funded this project through a sub-contract to K.D. Anderson from a larger Special Projects Award (grant number FP0020773) from the Craig H. Neilsen Foundation.

Recovery of forepaw gripping ability and reorganization of cortical motor control following cervical spinal cord injuries in mice.

Previous studies using a grip strength meter (GSM) revealed a loss of gripping ability following cervical hemisection injuries in mice, followed by partial recovery. Here, we assess whether normal gripping ability and the recovered gripping ability after cervical hemisection depend on the cerebral cortex. First, we assessed grip strength of both forepaws of 18-week-old C57Bl/6 mice before and after a left sensorimotor cortex lesion or right lateral hemisection at C5. Both lesions led to a complete loss of gripping ability by the right forepaw and caused only minor deficits in the left. After cortical lesions, gripping ability re-appeared at about 17 days post-injury, and grip strength recovered to near-normal levels by 24 days post-injury. After C5 hemisections, gripping ability re-appeared after 31 days post-injury in 50% of the mice. Follow-up experiments were then carried out in which 10-week-old mice received C4 hemisection injuries and were tested for 28 days; then mice received secondary lesions of the sensorimotor cortex ipsi- or contralateral to the hemisection. Younger mice with cervical hemisections recovered gripping ability between 12 and 28 days post-hemisection. Cortical lesions on the side contralateral to the hemisection led to a complete loss of recovered gripping ability in all mice; cortical lesions on the side ipsilateral to the hemisection also disrupted recovered gripping ability in some animals. Surprisingly, lesions of the cortex ipsilateral to the hemisection did not impair gripping ability of the contralateral (left) forepaw. Finally, we assessed the effects of a third lesion of whichever side of the sensorimotor cortex remained, so that the sensorimotor cortex was ablated bilaterally. Remarkably, gripping function by the forepaw contralateral to the original hemisection was completely unaffected, and the recovered gripping function by the forepaw ipsilateral to the hemisection was disrupted in only some of the animals. These results indicate a substantial reorganization of motor control of gripping function after cervical injuries in mice so that gripping ability by both forepaws becomes largely independent of cortical control.