Anatomical but not functional recovery from a sciatic nerve crush is enhanced by treatment with testosterone

Purpose: Until recently, there has been a limited amount of research compar ing functional and anatomical recovery following nerve injury. Previous stu dies emphasizing anatomical recovery (such as axonal number) have shown tha t testosterone promotes regeneration in crushed and transected nerves. The purpose of this study was to assess the effect of testosterone on the funct ional recovery of the sciatic nerve following a unilateral crush injury. Methods: Young adult male Sprague-Dawley rats were injected daily with eith er 500 mu g testosterone proprionate or vehicle alone. The recovery course was followed for six weeks using functional and behavioral testing. Behavio ral tests included a footprint gait analysis las a measure of motor functio n), response to a skin pinch, and warm water withdrawal (measures of sensor y function). Results: Immediately following surgery, all tests indicated complete denerv ation to the leg distal to the crush site. Anatomical analysis revealed a 2 2 % increase in the number of axons in testosterone treated animals at 6 we eks post-crush, but no indication of differences in functional recovery. Th e results of behavioral testing indicated only minor differences in functio nal recovery as a result of testosterone treatment. Conclusion: The results indicate the need for a detailed comparison between anatomical regeneration and functional recovery. An increase in axon numbe r alone may not be an accurate indicator of successful regeneration.