Early and Late Changes in Lower Urinary Tract Function Following Experimental Cervical Spinal Cord Injury

Keywords: animal model, neurophysiological monitoring, spinal cord injury, evoked potentials, cervical spine

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     Lower urinary tract(LUT) dysfunction is a major source of morbidity after spinal cord injury(SCI), irrespective of spinal level. Experimental studies of post-SCI LUT function, however, have investigated only thoracic injuries, and paradoxically show recovery of normal LUT function behaviorally. Few studies have shown abnormal LUT function electrophysiologically similar to that seen clinically. Developing translational SCI therapies requires better understanding of the relationship between behavior and neurophysiology in clinically relevant injury models.
     We introduce a novel preclinical model that defines acute and chronic behavioral and electrophysiologic changes in LUT function after cervical contusion SCI.
     Mid-cervical(C4-5) unilateral(n=24) or bilateral(n=24) contusion injuries were produced in adult Sprague–Dawley rats. Six naïve rats served as controls.
     LUT function was evaluated electrophysiologically via transurethral cystometry(7.5 ml/hr) and EUS electromyography. SCI animals were assessed on post-injury days 7,14,28,56. Behavioral assessment of LUT function was measured by daily manual bladder expression for retained urine.
     Naïve animals demonstrated normal LUT behavior and electrophysiology. Unilateral injury animals demonstrated normal LUT behavior throughout, and normal electrophysiology at early time-points(post-injury days 7,14), but abnormal electrophysiology at late time-points(post-injury days 28,56). Bilateral injury animals demonstrated significant early LUT behavior dysfunction(<14 days post-injury) and concomitant abnormal electrophysiology(post-injury days 7,14). After 14 days, bilateral injury animals recovered normal LUT behavior, but had persistent late abnormal electrophysiology(post-injury days 28,56).
     This is a rat study.
     Using a novel translational SCI model, we observed close correlation between LUT behavior and electrophysiology acutely.
     We found that electrophysiology assessment may serve as a more sensitive indicator of chronic unilateral and bilateral SCI.


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