Locomotor behavior of bonnet monkeys after spinal contusion injury: Footprint study

Abstract

Analysis of gait functions following spinal cord injury has been widely studied in rats, mice but limited in primates. This investigation was performed to quantitatively analyze the degree of functional recovery in bipedal locomotion in bonnet monkeys after induced spinal cord contusion. The degree of locomotor recovery was examined by measuring four gait variables, viz., tip of opposite foot (TOF), print-length (PL), toe-spread (TS), and intermediary toe-spread (IT) from the recorded hindlimb prints of monkeys using ink and paper technique. Contusion was induced in spinal cord at T12-L1 level in anaesthetized monkeys by using the Allen's weight drop technique. Postoperatively, all spinal contused animals initially showed a significant decrease in TOF, which then gradually increased for longer duration and attained the near normal values by the sixth month. On the other hand, PL, TS, and IT variables in hindlimb prints of contused animals were found to dramatically increase initially and then slowly decrease subsequently. Later there was a recovery to insignificant levels which differed from the corresponding preoperative values by the fifth month. The observations of this study suggest that the functional contributions of the spared fibers, especially in ventral and ventrolateral funiculi, through collateral sprouts or synaptic plasticity that were formed in the contused spinal cord may be responsible for substantial recovery of hindlimb movements. Moreover, based on analysis of footprint variables observed in locomotion in these subjected monkeys, we understand that spinal automatism and development of responses by afferent stimuli from outside the cord could possibly contribute to recovery of the paralyzed hindlimbs.

Locomotor recovery after spinal cord hemisection/contusion injures in bonnet monkeys: Footprint testing—a minireview

“…All the animals that underwent SC lesions did not initially place their foot properly on the surface and a severe dragging of their toes was observed while they walked on runways. While the bipedal locomotion of animals with SC contusion lesion on the runway subsequently improved, we found the PL measurement initially increased in both right and left hindlimbs of animals to support their entire body weight for maintaining their postural support with both hindlimbs on the surface (Suresh Babu et al, ). This indirectly suggests that the normal animal did not place its heel completely on the surface while walking on the runway.…”

“…Similar to rodent studies, we have recently examined the extent and time course of spontaneous recovery of bipedal pattern of locomotion after inflicting SC hemisection (Suresh Babu and Namasivayam, ; Suresh Babu et al, ) and contusion lesions (Suresh Babu et al, ) (Figs. A–C) in bonnet macaque monkeys by applying the footprint analysis technique.…”

“…The recording of footprints of trained monkeys was made by using nontoxic ink and white paper (Figs. C and D) and the technical details of footprint recordings during bipedal locomotion of monkeys on runways were described in our earlier reports (Suresh Babu and Namasivayam, ; Suresh Babu et al, ). Representative hindlimb‐prints of monkeys recorded during bipedal locomotion on the wide runway and treadmill are illustrated in Figures to .…”

“…). This deficit may be due to the inability of lesioned animals to maintain their center of gravity within the base of the foot and to increase the area of contact of their foot on the ground with the toes spread further apart (Suresh Babu and Namasivayam, ; Suresh Babu et al, ). Furthermore, this also represents a clear sign of functional deficits in locomotion that might be associated with the damage to propriospinal neurons (Kunkel‐Bagden et al, ; Stokes and Reier, ).…”

“…Similar type of study performed by us in bonnet monkey model is found to support this concept. In our primate study, we inflicted unilateral hemisection on the right side of SC, including the complete damage to one dorsal, lateral, ventral funicular region and leaving the other left side of all funiculi intact in SC of bonnet monkeys (Suresh Babu and Namasivayam, ; Suresh Babu et al, ). In another study, we induced contusive injury by the dorsal approach to the exposed SC of bonnet monkeys using the weight‐drop technique, thereby causing damage to gray matter mainly involving dorsal/dorsolateral funiculi and sparing significant parts of ventral funiculi in both side of SC (Suresh Babu et al, ) (Figs.…”