Duration of neuronal stretch correlates with functional loss

Postoperative cranial nerve weakness or paralysis is not uncommon in many o tolaryngologic surgical procedures. Our study used a rat model to test the hypothesis that the length of time that a nerve is under tension may be an important variable in the amount of postoperative paresis, Forty Sprague-Da wley rats were divided into 4 groups that underwent either a sham operation or a traction injury for 1, 2, or 5 minutes, The traction injury was perfo rmed with a vessel loop placed around the sciatic nerve with 50 g of tensio n. Traction injury for 1 or 2 minutes did not result in any statistical dif ferences in the motor capabilities of the lower limb, However, those animal s with a stretch injury for 5 minutes had a significant loss of function (P < 0.01) when compared with all other groups. Histologic examination of ner ves harvested on postoperative day 7 showed no evidence of mechanical injur y. This study demonstrates that even minimal tension, if maintained for a s ignificant amount of time, may result in postoperative weakness.