Longitudinal electrophysiological changes after cervical hemi-contusion spinal cord injury in rats

• Published in: Neuroscience letters 2018-01, Vol.664, p.116-122
• Main Authors: Huang, Zucheng, Li, Rong, Liu, Junhao, Huang, Zhiping, Hu, Yong, Wu, Xiaoliang, Zhu, Qingan
• Format: Article
• Language: English
• Subjects: Behavioral assessments; Hemi-contusion; Motor evoked potentials; Somatosensory evoked potentials; Spinal cord injury
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/j.neulet.2017.11.019

•Cervical hemi-contusion spinal cord injury leads to ipsilateral forelimb impairment and unilateral spinal cord lesion.•Reliable electrophysiological test could only be obtained in chronic phase due to unstable SEPs and MEPs in acute spinal cord injury.•Longitudinal electrophysiology changes reflect the neurological impairment after hemi-contusion SCI. To evaluate the longitudinal somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) characterization from acute to chronic injury following cervical hemi-contusion spinal cord injury (SCI) in rats, and correlate the MEPs & SEPs to the behavioral outcomes. Fifteen adult male Sprague-Dawley rats were subjected to the hemi-contusion spinal cord injury at C5. Forelimb MEPs & SEPs were applied to 5 animals before injury and 3h, 1d, 3d, 1w, 2w, 4w and 8w after injury respectively. Forelimb functional assessments, including Montoya staircase task and cylinder rearing test, were conducted on another 10 animals before injury and at 2w, 4w and 8w after injury respectively, as well as histological analysis of the cord at 8w after injury. A group correlation was performed between the MEPs & SEPs and behavioral outcomes. The hemi-contusion injury resulted in unilateral tissue damage at the epicenter with loss of the ventral horns and lateral funiculus. Both ipsilateral and contralateral forelimb MEPs showed latency prolongation and amplitude reduction at 3h after injury. The MEPs amplitude increased with time after injury, but the ipsilateral amplitude was persistently lower than the contralateral amplitude. The ipsilateral MEPs latency increased with time after injury and was significantly longer than the contralateral MEPs latency. The ipsilateral SEPs amplitude dropped after injury and stayed at a lower level up to 8 weeks. There was no difference in the SEPs latency among time points and between sides. At 8 weeks after injury, the ipsilateral forelimb grasped 30% pellets while the contralateral forelimb close to 81%. An obvious decreased usage of the ipsilateral paw and increased usage of the contralateral paw were observed in rearing test after injury. The MEPs latency and amplitude correlated significantly with the forelimb motor function. Cervical hemi-contusion SCI led to persistent changes in MEPs & SEPs of the ipsilateral forelimb, ipsilateral impairment in motor function and unilateral cord tissue damage. Reliable electrophysiology assessment was obtained in chronic phase due to unstable MEP