Cervical spinal cord injury at birth permanently disrupts forelimb function in goal-directed reaching. Transplants of fetal spinal cord tissue permit the development of skilled forelimb use and associated postural adjustments (, companion article). The aim of this study was to determine whether transplants of fetal spinal cord tissue support the remodeling of supraspinal and segmental pathways that may underlie recovery of postural reflexes and forelimb movements. Although brainstem-spinal and segmental projections to the cervical spinal cord are present at birth, skilled forelimb reaching has not yet developed. Three-day-old rats received a cervical spinal cord overhemisection with or without transplantation of fetal spinal cord tissue (embryonic day 14); unoperated pups served as normal controls. Neuroanatomical tracing techniques were used to examine the organization of CNS pathways that may influence target-directed reaching. In animals with hemisections only, corticospinal, brainstem-spinal, and dorsal root projections within the spinal cord were decreased in number and extent. In contrast, animals receiving hemisections plus transplants exhibited growth of these projections throughout the transplant and over long distances within the host spinal cord caudal to the transplant. Raphespinal axons were apposed to numerous propriospinal neurons in control and transplant animals; these associations were greatly reduced in the lesion-only animals. These observations suggest that after neonatal cervical spinal cord injury, embryonic transplants support axonal growth of CNS pathways and specifically supraspinal input to propriospinal neurons. We suggest that after neonatal spinal injury in the rat, the transplant-mediated reestablishment of supraspinal input to spinal circuitry is the mechanism underlying the development of target-directed reaching and associated postural adjustments.

This study aims to determine the relationship between spinal cord perfusion pressure (SCPP) and breathing function in patients with acute cervical traumatic spinal cord injuries.

This study examines and compares the walking function in contusion and distraction spinal cord injury (SCI) mechanisms. Moderate contusion and distraction SCIs were surgically induced between C5 and C6 in Sprague-Dawley male rats. The CatWalk system was used to perform gait analysis of walkway walking. The ladder rung walking test was used to quantify skilled locomotor movements of ladder rung walking. It was found that the inter-paw coordination, paw support, front paw kinematics, hind paw kinematics, and skilled movements were significantly different before and after contusion and distraction. Step sequence duration, diagonal support, forelimb intensity, forelimb duty cycle, forelimb paw angle, and forelimb swing speed were more greatly affected in distraction than in contusion at 2 weeks post-injury, whereas hindlimb stand was more greatly affected in contusion than in distraction at 8 weeks post-injury. After 8 weeks post-injury, diagonal coupling-variation, girdle coupling-variation, ipsilateral coupling-mean, forelimb maximum contact at, forelimb intensity, forelimb paw angle, and number of forelimb misplacements recovered to normal in contusion but not in distraction, whereas step sequence duration, ipsilateral coupling-variation, forelimb stand, forelimb duty cycle, hindlimb swing duration, hindlimb swing speed, and number of forelimb slips recovered to normal in distraction but not in contusion. Some of the behavioral outcomes, but not the others, were linearly correlated with the histological outcomes. In conclusion, walking deficits and recovery can be affected by the type of common traumatic SCI.

Spinal cord injury is a severe condition, resulting in specific neurological symptoms depending on the level of damage. Approximately 60% of spinal cord injuries affect the cervical spinal cord, resulting in complete or incomplete tetraplegia and higher mortality rates than injuries of the thoracic or lumbar region. Although cervical spinal cord injuries frequently occur in humans, there are few clinically relevant models of cervical spinal cord injury. Animal models are critical for examining the cellular and molecular manifestations of human cervical spinal cord injury, which is not feasible in the clinical setting, and to develop therapeutic strategies. There is a limited number of studies using cervical, bilateral contusion SCI and providing a behavioral assessment of motor and sensory functions, which is partly due to the high mortality rate and severe impairment observed in severe cervical SCI models. The goal of this study was to develop a mouse model of cervical contusion injury with moderate severity, resulting in an apparent deficit in front and hindlimb function but still allowing for self-care of the animals. In particular, we aimed to characterize a mouse cervical injury model to be able to use genetic models and a wide range of viral techniques to carry out highly mechanistic studies into the cellular and molecular mechanisms of cervical spinal cord injury. After inducing a bilateral, cervical contusion injury at level C5, we followed the recovery of injured and sham-uninjured animals for eight weeks post-surgery. Hindlimb and forelimb motor functions were significantly impaired immediately after injury, and all mice demonstrated partial improvement over time that remained well below that of uninjured control mice. Mice also displayed a significant loss in their sensory function throughout the testing period. This loss of sensory and motor function manifested as a reduced ability to perform skilled motor tasks in all of the injured mice. Here, we describe a new mouse model of moderate bilateral cervical spinal cord injury that does not lead to mortality and provides a comprehensive assessment of histological and behavioral assessments. This model will be useful in enhancing our mechanistic understanding of cervical spinal cord injury and in the development of treatments targeted at promoting neuroprotection, neuroplasticity, and functional recovery after cervical SCI.

Cervical radiculopathy is a common disease in clinical practice. However, the symptoms are not confined to the affected spinal cord segment indicated by magnetic resonance imaging (MRI) findings. In the present study, we measured c-Fos and c-Jun expression in ipsilateral and adjacent cervical spinal cord segments following C7 nerve root rhizotomy, to determine whether there is a neural pathway between adjacent cervical spinal cord segments. Forty-eight adult male Wistar rats were randomly divided into two groups: the C7 rhizotomy group (rhizotomy group, n=24) and the sham-operated group (sham group, n=24). The right C7 nerve root was completely cut off in the rhizotomy group, while it was exposed but not cut in the sham group. The expression of c-Fos and c-Jun in cervical spinal cord segments was detected by immunohistochemistry at 2 and 4 h after surgery. We observed that the number of c-Fos- and c-Jun-positive neurons in ipsilateral C5-7 segments were significantly increased at 2 and 4 h after C7 nerve root rhizotomy (P<0.05 vs. the sham group). The location of c-Fosand c-Jun-positive neurons in C5-7 gray matter was similar in the rhizotomy and sham groups, which was mainly in lamina IX of the anterior horn and laminae I-II of the dorsal horn of the spinal cord. However, the number of c-Fos- and c-Jun-positive neurons in the C5-7 gray matter was significantly reduced at 4 h after surgery compared with the number 2 h after surgery. The location of c-Fos- and c-Jun-positive neurons at 4 h was similar with that at 2 h. Therefore, there may be a neural pathway between ipsilateral adjacent cervical spinal cord segments. This may be one possible explanation as to why the radicular symptoms of cervical radiculopathy are not confined to the affected spinal cord segment shown by MRI.

Excess glutamate release and associated neurotoxicity contributes to cell death after spinal cord injury (SCI). Indeed, delayed administration of glutamate receptor antagonists after SCI in rodents improves tissue sparing and functional recovery. Despite their therapeutic potential, most glutamate receptor antagonists have detrimental side effects and have largely failed clinical trials. Topiramate is an AMPA-specific, glutamate receptor antagonists that is FDA-approved to treat CNS disorders. In the current study we tested whether topiramate treatment is neuroprotective after cervical contusion injury in rats. We report that topiramate, delivered 15-minutes after SCI, increases tissue sparing and preserves oligodendrocytes and neurons when compared to vehicle treatment. In addition, topiramate is more effective than the AMPA-receptor antagonist, NBQX. To the best of our knowledge, this is the first report documenting a neuroprotective effect of topiramate treatment after spinal cord injury.

Opioid overdose suppresses brainstem respiratory circuits, causes apnoea and may result in death. Epidural electrical stimulation (EES) at the cervical spinal cord facilitated motor activity in rodents and humans, and we hypothesized that EES of the cervical spinal cord could antagonize opioid-induced respiratory depression in humans. Eighteen patients requiring surgical access to the dorsal surface of the spinal cord between C2 and C7 received EES or sham stimulation for up to 90 s at 5 or 30 Hz during complete (OFF-State) or partial suppression (ON-State) of respiration induced by remifentanil. During the ON-State, 30 Hz EES at C4 and 5 Hz EES at C3/4 increased tidal volume and decreased the end-tidal carbon dioxide level compared to pre-stimulation control levels. EES of 5 Hz at C5 and C7 increased respiratory frequency compared to pre-stimulation control levels. In the OFF-State, 30 Hz cervical EES at C3/4 terminated apnoea and induced rhythmic breathing. In cadaveric tissue obtained from a brain bank, more neurons expressed both the neurokinin 1 receptor (NK1R) and somatostatin (SST) in the cervical spinal levels responsive to EES (C3/4, C6 and C7) compared to a region non-responsive to EES (C2). Thus, the capacity of cervical EES to oppose opioid depression of respiration may be mediated by NK1R+/SST+ neurons in the dorsal cervical spinal cord. This study provides proof of principle that cervical EES may provide a novel therapeutic approach to augment respiratory activity when the neural function of the central respiratory circuits is compromised by opioids or other pathological conditions. KEY POINTS: Epidural electrical stimulation (EES) using an implanted spinal cord stimulator (SCS) is an FDA-approved method to manage chronic pain. We tested the hypothesis that cervical EES facilitates respiration during administration of opioids in 18 human subjects who were treated with low-dose remifentanil that suppressed respiration (ON-State) or high-dose remifentanil that completely inhibited breathing (OFF-State) during the course of cervical surgery. Dorsal cervical EES of the spinal cord augmented the respiratory tidal volume or increased the respiratory frequency, and the response to EES varied as a function of the stimulation frequency (5 or 30 Hz) and the cervical level stimulated (C2-C7). Short, continuous cervical EES restored a cyclic breathing pattern (eupnoea) in the OFF-State, suggesting that cervical EES reversed the opioid-induced respiratory depression. These findings add to our understanding of respiratory pattern modulation and suggest a novel mechanism to oppose the respiratory depression caused by opioids.

Transcutaneous spinal cord stimulation (TSCS) has demonstrated potential to beneficially modulate spinal cord motor and autonomic circuitry. We are interested in pairing cervical TSCS with other forms of nervous system stimulation to enhance synaptic plasticity in circuits serving hand function. We use a novel configuration for cervical TSCS in which the anode is placed anteriorly over ~C4-C5 and the cathode posteriorly over ~T2-T4. We measured the effects of single pulses of TSCS paired with single pulses of motor cortex or median nerve stimulation timed to arrive at the cervical spinal cord at varying intervals. In 13 participants with and 15 participants without chronic cervical spinal cord injury, we observed that subthreshold TSCS facilitates hand muscle responses to motor cortex stimulation, with a tendency toward greater facilitation when TSCS is timed to arrive at cervical synapses simultaneously or up to 10 milliseconds after cortical stimulus arrival. Single pulses of subthreshold TSCS had no effect on the amplitudes of median H-reflex responses or F-wave responses. These findings support a model in which TSCS paired with appropriately timed cortical stimulation has the potential to facilitate convergent transmission between descending motor circuits, segmental afferents, and spinal motor neurons serving the hand. Studies with larger numbers of participants and repetitively paired cortical and spinal stimulation are needed.

High-cervical spinal cord injury often disrupts respiratory motor pathways and disables breathing in the affected population. Moreover, cervically injured individuals are at risk for developing acute lung injury, which predicts substantial mortality rates. While the correlation between acute lung injury and spinal cord injury has been found in the clinical setting, the field lacks an animal model to interrogate the fundamental biology of this relationship. To begin to address this gap in knowledge, we performed an experimental cervical spinal cord injury (N = 18) alongside sham injury (N = 3) and naïve animals (N = 15) to assess lung injury in adult rats. We demonstrate that animals display some early signs of lung injury two weeks post-spinal cord injury. While no obvious histological signs of injury were observed, the spinal cord injured cohort displayed significant signs of metabolic dysregulation in multiple pathways that include amino acid metabolism, lipid metabolism, and N-linked glycosylation. Collectively, we establish for the first time a model of lung injury after spinal cord injury at an acute time point that can be used to monitor the progression of lung damage, as well as identify potential targets to ameliorate acute lung injury.

Accumulating evidence indicate that the neuropeptide urotensin II and urotensin II receptors are expressed in subsets of mammal spinal motoneurons. In fact, a role for the peptide in the regulation of motoneuron function at neuromuscular junction has been suggested, while roles for urotensin II at central synapses in spinal cord have never been addressed. We found that urotensin II receptors were closely associated with cholinergic terminals apposed to a subset of motoneuron and non-motoneuron cell bodies in the ventral horn of the adult mouse cervical spinal cord; urotensin II receptor was also expressed on non-cholinergic nerve terminals. In particular, urotensin II receptor appeared associated with both large cholinergic C-boutons and standard cholinergic terminals contacting some motoneuron perikarya. Cholinergic nerve terminals from mouse cervical spinal cord were equipped with functional presynaptic urotensin II receptors linked to excitation of acetylcholine release. In fact, functional experiments conducted on cervical spinal synaptosomes demonstrated a urotensin II evoked calcium-dependent increase in [(3)H]acetylcholine release pharmacologically verified as consistent with activation of urotensin II receptors. In spinal cord these actions would facilitate cholinergic transmission. These data indicate that, in addition to its role at the neuromuscular junction, urotensin II may control motor function through the modulation of motoneuron activity within the spinal cord.

Cervical injuries are the most common form of SCI. In this study, we used a neuromodulatory approach to promote skilled movement recovery and repair of the corticospinal tract (CST) after a moderately severe C4 midline contusion in adult rats. We used bilateral epidural intermittent theta burst (iTBS) electrical stimulation of motor cortex to promote CST axonal sprouting and cathodal trans-spinal direct current stimulation (tsDCS) to enhance spinal cord activation to motor cortex stimulation after injury. We used Finite Element Method (FEM) modeling to direct tsDCS to the cervical enlargement. Combined iTBS-tsDCS was delivered for 30min daily for 10days. We compared the effect of stimulation on performance in the horizontal ladder and the Irvine Beattie and Bresnahan forepaw manipulation tasks and CST axonal sprouting in injury-only and injury+stimulation animals. The contusion eliminated the dorsal CST in all animals. tsDCS significantly enhanced motor cortex evoked responses after C4 injury. Using this combined spinal-M1 neuromodulatory approach, we found significant recovery of skilled locomotion and forepaw manipulation skills compared with injury-only controls. The spared CST axons caudal to the lesion in both animal groups derived mostly from lateral CST axons that populated the contralateral intermediate zone. Stimulation enhanced injury-dependent CST axonal outgrowth below and above the level of the injury. This dual neuromodulatory approach produced partial recovery of skilled motor behaviors that normally require integration of posture, upper limb sensory information, and intent for performance. We propose that the motor systems use these new CST projections to control movements better after injury.

In the brain, specific signaling pathways localized in highly organized regions called niches allow the persistence of a pool of stem and progenitor cells that generate new neurons in adulthood. Much less is known about the spinal cord where a sustained adult neurogenesis is not observed. Moreover, there is scarce information concerning cell proliferation in the adult mammalian spinal cord and virtually none in aging animals or humans. We performed a comparative morphometric and immunofluorescence study of the entire cervical region (C1-C8) in young (5 mo.) and aged (30 mo.) female rats. Serum prolactin (PRL), a neurogenic hormone, was also measured. Gross anatomy showed a significant age-related increase in size of all of the cervical segments. Morphometric analysis of cresyl violet stained segments also showed a significant increase in the area occupied by the gray matter of some cervical segments of aged rats. The most interesting finding was that both the total area occupied by neurons and the number of neurons increased significantly with age, the latter increase ranging from 16% (C6) to 34% (C2). Taking the total number of cervical neurons the age-related increase ranged from 19% (C6) to 51% (C3), C3 being the segment that grew most in length in the aged animals. Some bromodeoxyuridine positive-neuron specific enolase negative (BrdU(+)-NSE(-)) cells were observed and, occasionally, double positive (BrdU(+)-NSE(+)) cells were detected in some cervical segments of both young and aged rats groups. As expected, serum PRL increased markedly with age. We propose that in the cervical spinal cord of female rats, both maturation of pre-existing neuroblasts and/or possible neurogenesis occur during the entire life span, in a process in which PRL may play a role.

Cervical spinal cord injury (CSCI) is devastating and costly. Previous research has demonstrated that diaphragm pacing (DPS) is safe and improves respiratory mechanics. This may decrease hospital stays, vent days, and costs. We hypothesized DPS implantation would facilitate liberation from ventilation and would impact hospital charges.

[Purpose] The purpose of this study was to make an experimental model of cervical spinal cord injury (CSCI) using Wistar rats, in order to analyze the influence of CSCI on the respiratory function. [Subjects] Thirty-two male 12-week-old Wistar rats were used. [Methods] The CSCI was made at the levels from C3 to C7, and we performed pneumotachography and electromyography (EMG) on the diaphragm. Computed tomography was used to determine the level of spinal cord damage. [Results] After the operation, the tidal volume of the rats with a C3 level injury decreased to approximately 22.3% of its pre-injury value. In addition, in the same rats, the diaphragmatic electromyogram activity decreased remarkably. Compared with before CSCI, the tidal volume decreased to 78.6% of its pre-injury value in CSCI at the C5 level, and it decreased to 94.1% of its pre-injury value in CSCI at the C7 level. [Conclusion] In the rats that sustained a CSCI in this study, the group of respiratory muscles that receive innervation from the thoracic spinal cord was paralyzed. Therefore, the EMG signal of the diaphragm increased. These results demonstrate that there is a relationship between respiratory function and the level of CSCI.

Spinal cord injury (SCI) above cervical level 4 disrupts descending axons from the medulla that innervate phrenic motor neurons, causing permanent paralysis of the diaphragm. Using an ex vivo preparation in neonatal mice, we have identified an excitatory spinal network that can direct phrenic motor bursting in the absence of medullary input. After complete cervical SCI, blockade of fast inhibitory synaptic transmission caused spontaneous, bilaterally coordinated phrenic bursting. Here, spinal cord glutamatergic neurons were both sufficient and necessary for the induction of phrenic bursts. Direct stimulation of phrenic motor neurons was insufficient to evoke burst activity. Transection and pharmacological manipulations showed that this spinal network acts independently of medullary circuits that normally generate inspiration, suggesting a distinct non-respiratory function. We further show that this "latent" network can be harnessed to restore diaphragm function after high cervical SCI in adult mice and rats.

To study postoperative Health-Related Quality of Life (HRQOL) after instrumented fusion for fresh subaxial cervical trauma and the effect of spinal cord injury (SCI).

Previous studies suggest locomotion training could be an effective non-invasive therapy after spinal cord injury (SCI) using primarily acute thoracic injuries. However, the majority of SCI patients have chronic cervical injuries. Regaining hand function could significantly increase their quality of life. In this study, we used a clinically relevant chronic cervical contusion to study the therapeutic efficacy of rehabilitation in forelimb functional recovery. Nude rats received a moderate C5 unilateral contusive injury and were then divided into two groups with or without Modified Montoya Staircase (MMS) rehabilitation. For the rehabilitation group, rats were trained 5 days a week starting at 8 weeks post-injury (PI) for 6 weeks. All rats were assessed for skilled forelimb functions with MMS test weekly and for untrained gross forelimb locomotion with grooming and horizontal ladder (HL) tests biweekly. Our results showed that MMS rehabilitation significantly increased the number of pellets taken at 13 and 14 weeks PI and the accuracy rates at 12 to 14 weeks PI. However, there were no significant differences in the grooming scores or the percentage of HL missteps at any time point. Histological analyses revealed that MMS rehabilitation significantly increased the number of serotonergic fibers and the amount of presynaptic terminals around motor neurons in the cervical ventral horns caudal to the injury and reduced glial fibrillary acidic protein (GFAP)-immunoreactive astrogliosis in spinal cords caudal to the lesion. This study shows that MMS rehabilitation can modify the injury environment, promote axonal sprouting and synaptic plasticity, and importantly, improve reaching and grasping functions in the forelimb, supporting the therapeutic potential of task-specific rehabilitation for functional recovery after chronic SCI.

Oxidative damage to the diaphragm as a result of cervical spinal cord injury (SCI) promotes muscle atrophy and weakness. Respiratory insufficiency is the leading cause of morbidity and mortality in cervical spinal cord injury (SCI) patients, emphasizing the need for strategies to maintain diaphragm function. Hyperbaric oxygen (HBO) increases the amount of oxygen dissolved into the blood, elevating the delivery of oxygen to skeletal muscle and reactive oxygen species (ROS) generation. It is proposed that enhanced ROS production due to HBO treatment stimulates adaptations to diaphragm oxidative capacity, resulting in overall reductions in oxidative stress and inflammation. Therefore, we tested the hypothesis that exposure to HBO therapy acutely following SCI would reduce oxidative damage to the diaphragm muscle, preserving muscle fiber size and contractility. Our results demonstrated that lateral contusion injury at C3/4 results in a significant reduction in diaphragm muscle-specific force production and fiber cross-sectional area, which was associated with augmented mitochondrial hydrogen peroxide emission and a reduced mitochondrial respiratory control ratio. In contrast, rats that underwent SCI followed by HBO exposure consisting of 1 h of 100% oxygen at 3 atmospheres absolute (ATA) delivered for 10 consecutive days demonstrated an improvement in diaphragm-specific force production, and an attenuation of fiber atrophy, mitochondrial dysfunction and ROS production. These beneficial adaptations in the diaphragm were related to HBO-induced increases in antioxidant capacity and a reduction in atrogene expression. These findings suggest that HBO therapy may be an effective adjunctive therapy to promote respiratory health following cervical SCI.

Spinal cord injury (SCI) triggers a complex cellular response at the injury site, leading to the formation of a dense scar tissue. Despite this local tissue remodeling, the consequences of SCI at the cellular level in distant rostral sites (i.e., brain), remain unknown. In this study, we asked whether cervical SCI could alter cell dynamics in neurogenic areas of the adult rat forebrain. To this aim, we quantified BrdU incorporation and determined the phenotypes of newly generated cells (neurons, astrocytes, or microglia) during the subchronic and chronic phases of injury. We find that subchronic SCI leads to a reduction of BrdU incorporation and neurogenesis in the olfactory bulb and in the hippocampal dentate gyrus. By contrast, subchronic SCI triggers an increased BrdU incorporation in the dorsal vagal complex of the hindbrain, where most of the newly generated cells are identified as microglia. In chronic condition 90 days after SCI, BrdU incorporation returns to control levels in all regions examined, except in the hippocampus, where SCI produces a long-term reduction of neurogenesis, indicating that this structure is particularly sensitive to SCI. Finally, we observe that SCI triggers an acute inflammatory response in all brain regions examined, as well as a hippocampal-specific decline in BDNF levels. This study provides the first demonstration that forebrain neurogenesis is vulnerable to a distal SCI.

Previous research has delineated the networks of brain structures involved in the perception of emotional auditory stimuli. These include the amygdala, insula, and auditory cortices, as well as frontal-lobe, basal ganglia, and cerebellar structures involved in the planning and execution of motoric behaviors. The aim of the current research was to examine whether emotional sounds also influence activity in the brainstem and cervical spinal cord. Seventeen undergraduate participants completed a spinal functional magnetic resonance imaging (fMRI) study consisting of two fMRI runs. One run consisted of three one-minute blocks of aversive sounds taken from the International Affective Digitized Sounds (IADS) stimulus set; these blocks were interleaved by 40-s rest periods. The other block consisted of emotionally neutral stimuli also drawn from the IADS. The results indicated a stark pattern of lateralization. Aversive sounds elicited greater activity than neutral sounds in the right midbrain and brainstem, and in right dorsal and ventral regions of the cervical spinal cord. Neutral stimuli, on the other hand, elicited less neural activity than aversive sounds overall; these responses were left lateralized and were found in the medial midbrain and the dorsal sensory regions of the cervical spinal cord. Together, these results demonstrate that aversive auditory stimuli elicit increased sensorimotor responses in brainstem and cervical spinal cord structures.