Neurophysiological and Spinal Cord Perfusion Changes at Dynamic Neck Positions in a Compressive Spinal Cord Injury Rat Model

Abstract

\n Background: Cervical spondylotic myelopathy (CSM) is a degenerative condition of the spine that caused by static and dynamic compression of the spinal cord. However, the pathophysiological changes at dynamic neck positions remain poor. This study investigated the interplay between neurophysiological and haemodynamic responses at dynamic neck positions in a chronic compressive spinal cord injury (CCSCI) rat model. Methods: Behavioural tests including Basso, Beattie, and Bresnahan scores and an inclined plane test were used to evaluate the motor function recovery. Combined examination of dynamic motor and somatosensory evoked potentials (DMEPs and DSSEPs, respectively) was performed regularly to evaluate the dynamic motor and sensory conduction of the cervical cord. At 4 weeks post-injury (wpi), dynamic magnetic resonance imaging (MRI) and dynamic laser Doppler flowmetry (LDF) were used to demonstrate the interstructure and spinal cord blood flow (SCBF) at the compression site at dynamic neck positions. Hematoxylin and eosin (HE) staining was performed to assess the cords pathological changes.Results: Behavioural tests and combined DMEPs and DSSEPs examination showed that spinal cord neurological function and dynamic neural conduction deteriorated gradually within a 4-week compression period. The DMEPs were mainly deteriorated upon flexion, while DSSEPs were upon all neck positions after the compression. At 4 wpi, dynamic MRI showed increased T2-weighted image (T2WI) signal intensities. Also, dynamic LDF demonstrated decreased SCBF at the spinal cord compression site. Both of them altered especially upon cervical flexion. The dynamic change in SCBF was significantly correlated with the change in DMEP amplitude upon flexion. Conclusions: This exploratory study revealed that changes in axonal conduction in the motor and somatosensory tracts of the spinal cord were significantly related to chronic compression time and neck position. Furthermore, spinal cord ischaemia may be intimately related to motor conduction dysfunction upon flexion in CCSCI models. These results indicated the potential for therapies targeting dynamic spinal cord perfusion to prevent progression and functional loss in CSM.