Surgical Replantation of Avulsed Lumbosacral Ventral Roots and Urodynamic Studies in a Rhesus Macaque (Macaca mulatta) Model of Cauda Equina/Conus Medullaris Injury and Repair

Abstract

Trauma to the thoracolumbar junction of the spine may result in injuries to the conus medullaris and the associated lumbosacral nerve roots, the cauda equina. Injured subjects commonly present clinically with a conus medullaris syndrome, which includes a flaccid paraparesis, sensory disturbance, neuropathic pain, and an underactive bladder syndrome. No present treatments are available to reverse the neurological deficits after a traumatic conus medullaris/cauda equina injury. Recent progress has been made with the development of clinically relevant experimental models. A lumbosacral ventral root avulsion (VRA) injury model in rats mimics key features of the clinical conus medullaris syndrome, and an acute replantation of ventral roots into the rat spinal cord promotes axonal regeneration and functional reinnervation of the lower urinary tract. Here, we demonstrate translation of the VRA injury and repair model and urodynamic studies as a functional outcome measure in nonhuman primates. The L6-S3 ventral roots are avulsed unilaterally in rhesus macaques and avulsed ventral roots are surgically replanted into the lateral funiculus of the spinal cord. Evoked micturition reflexes are evaluated by cystometrogram and urethral pressure recordings in male and female subjects both preoperatively and postoperatively in longitudinal studies.