Dynamic Motor Compensations with Permanent, Focal Loss of Forelimb Force after Cervical Spinal Cord Injury

Abstract

Incomplete cervical lesion is the most common type of human spinal cord injury (SCI) and causes permanent paresis of arm muscles, a phenomenon still incompletely understood in physiopathological and neuroanatomical terms. We performed spinal cord hemisection in adult rats at the caudal part of the segment C6, just rostral to the bulk of triceps brachii motoneurons, and analyzed the forces and kinematics of locomotion up to 4 months postlesion to determine the nature of motor function loss and recovery. A dramatic (50%), immediate and permanent loss of extensor force occurred in the forelimb but not in the hind limb of the injured side, accompanied by elbow and wrist kinematic impairments and early adaptations of whole-body movements that initially compensated the balance but changed continuously over the follow-up period to allow effective locomotion. Overuse of both contralateral legs and ipsilateral hind leg was evidenced since 5 days postlesion. Ipsilateral foreleg deficits resulted mainly from interruption of axons that innervate the spinal cord segments caudal to the lesion, because chronic loss (about 35%) of synapses was detected at C7 while only 14% of triceps braquii motoneurons died, as assessed by synaptophysin immunohistochemistry and retrograde neural tracing, respectively. We also found a large pool of propriospinal neurons projecting from C2-C5 to C7 in normal rats, with topographical features similar to the propriospinal premotoneuronal system of cats and primates. Thus, concurrent axotomy at C6 of brain descending axons and cervical propriospinal axons likely hampered spontaneous recovery of the focal neurological impairments.

Subacute Tissue Response to 3D Graphene Oxide Scaffolds Implanted in the Injured Rat Spinal Cord

“…The lesion model of choice was a right lateral hemisection of approximately 8 mm 3 (2 × 2 × 2) at the C6 segment, rostral to the bulk of triceps brachii motoneurons, previously demonstrated as a suitable model to evaluate therapeutic strategies aimed at promoting neural plasticity and repair. As it causes focal foreleg impairments attributable to the neural damage caused, both the impairments and their eventual recovery can be evidenced and measured in detail during locomotion by using careful functional and anatomical techniques . Some other advantages of this model include: a) higher clinical relevance, since most human spinal cord injuries occur in the cervical area and restoration of arm and hand function is a top priority for improving the quality of life of tetraplegic patients; b) the proximity of cervical motor nuclei to the lesion, so even short distance axonal growth could improve forelimb function; and c) regarding ethical considerations and requirements of animal care, this type of lesion typically causes damage in the ipsilateral forelimb with minimal contralateral forelimb and hindlimb sensorimotor impairments or autonomic dysfunction.…”

Photobiomodulation by diffusing optical fiber on spinal cord: A feasibility study in piglet model

“…However, HE staining results showed no structural injury in spinal cord tissue sections in each group. The reasons of difference between the molecular evidence and structural evidence may be that the pathological mechanism of light thermal injury for the spinal cord is different from that of other types of spinal cord injury . These findings in our study have not been reported according to our knowledge.…”

The Cortical Motor System in the Domestic Pig: Origin and Termination of the Corticospinal Tract and Cortico-Brainstem Projections

“…Aminostilbamidine differs from hydroxystilbamidine (Fluoro-Gold) only in an amino group substituting for a hydroxyl group, but otherwise these molecules are identical. The use of aminostilbamidine in the present work was based on our previous studies with this neural tracer in rodents (Collazos-Castro et al, 2005;Lucas-Osma and Collazos-Castro, 2009;López-Dolado et al, 2013) and pigs (Cerro et al, 2021) showing that: (1) it produces an intense, durable, and bleach-resistant fluorescent neuronal labeling in paraformaldehyde-fixed tissue;…”

“…Anatomical and physiological data for the cortical motor system have been extensively reported for rodents ( Terashima, 1995 ; Brösamle and Schwab, 2000 ; Collazos-Castro et al, 2006 ; López-Dolado et al, 2013 ; Moreno-López et al, 2016 ; Ueno et al, 2018 ; Steward et al, 2021 ), cats ( Hern et al, 1962 ; Illert et al, 1977 ; Groos et al, 1978 ; Alstermark et al, 1991 ; Canedo and Lamas, 1993 ; Ghosh, 1997 ; Salimi and Martin, 2004 ; Jankowska et al, 2006 ), and primates ( Kuypers, 1962 ; Phillips and Porter, 1964 ; Dum and Strick, 1991 , 1996 , 2002 ; Galea and Darian-Smith, 1994 ; Rosenzweig et al, 2009 ; Alstermark et al, 2011 ; Witham et al, 2016 ), whereas little information is available for pigs despite their increasing use in neurological research. Earliest retrograde neural tracing studies injected horseradish peroxidase (HRP) into the cervical and lumbar spinal cord, finding several cortical regions with spinal projections in cats and monkeys ( Coulter et al, 1976 ; Groos et al, 1978 ).…”