Compensatory Locomotor Adjustments of Rats with Cervical or Thoracic Spinal Cord Hemisections

Abstract

The accurate measurement of behavioral compensation after CNS trauma, such as spinal cord injury, is important when assessing the functional effects of injury and treatment in animal models. We investigated the locomotor abilities of rats with unilateral thoracic or cervical spinal cord injuries using a locomotor rating (BBB) scale, reflex tests, and quantitative kinetic measurements. The BBB rating scale indicated that thoracic spinal hemisected (TH) rats had more severely affected hindlimbs compared to cervical spinal hemisected (CH) and sham-operated animals. Kinetic measurements revealed that CH and TH animals moved with different ground reaction force patterns, which nevertheless shared some similarities with each other and with the gait patterns of rats with different unilateral CNS lesions. Uninjured rats typically had an equal distribution of their body weight over the forelimbs and hind limbs, and used their forelimbs predominantly for braking while using their hind limbs mostly for propulsion. CH rats bore more weight on their hind limbs than their forelimbs, while TH animals bore more weight on their forelimbs than their hind limbs. Neither CH nor TH rats used the forelimb ipsilateral to the spinal hemisection for net braking or propulsion. The hindlimb contralateral to the hemisection was placed on the ground prematurely during the stride cycle for both CH and TH animals. The altered kinetics of the locomotor pattern in hemisected animals resulted in changes in the oscillations of total body potential and kinetic energies. These two forms of energy oscillate synchronously in intact locomoting rats, but were asynchronous during parts of the stride cycle in spinal hemisected animals. We conclude that rats develop a general compensatory response for unilateral CNS lesions, which may help stabilize the animal during locomotion.

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

“…In agreement with previous studies of quadrupeds with partial SCI, 4,5,8,16,36 whole-body compensations developed in rats with C6 hemisection that contributed to maintaining balance and/or to improve the global locomotor performance (Fig. 10).…”

“…64 Trotting Long-Evans rats did not save energy by this mechanism in the normal condition, although they did it during parts of the stride after spinal cord hemisection at C3. 16 The extent to which energy transfer operates at walking velocities in our Wistar rats is uncertain, because we did not study the …”

“…This may explain why human stepping-like movements are easier to induce aftercervical than thoracic SCI, 9 and also the chronic weakness detected in human arm muscles that receive innervation from spinal levels just caudal to the lesion site. 10 The loss and recovery of forelimb motor function has been studied in several models of cervical SCI in rats, 4,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] cats, [28][29][30] and primates. [31][32][33][34][35] All those studies demonstrated some extent of spontaneous motor function recovery, albeit with persisting deficits as a consequence of interruption of descending axonal tracts or segmental neuronal death.…”

“…Despite these advances, there is still a need of cervical SCI models in which motor performance is comprehensively assessed in the long term to determine the motor components that show recovery and to link the chronic deficits with the neuroanatomical damage. Moreover, motor compensations always coexist with associated impairments in limb synergies, 4,5,8,16,21,36 complicating the interpretation and quantification of spontaneous and treatment-induced functional recovery and demanding the combined use of kinetic, kinematical, electrophysiological, and anatomical techniques for appropriate assessment.…”

Kinematics and Ground Reaction Force Determination: A Demonstration Quantifying Locomotor Abilities of Young Adult, Middle-aged, and Geriatric Rats

“…Further, kinematic and kinetic analysis of locomotion has been used to describe locomotor alterations in a variety of nervous system conditions where other forms of evaluation would be unsuccessful. 8,[23][24][25]27 The use of sensitive measures becomes especially important when evaluating potential therapeutants for various models of disease. If a test is not sensitive enough to discern an effect of a potential therapeutant the experimenter runs the risk of committing a type-II statistical error (i.e.…”