Effects of repeated crush injuries on motor functional recovery of the sciatic nerve.
OBJECTIVE
The present study was conducted to examine whether repeated crush injuries have significant effects on motor functional recovery of peripheral nerves.


METHODS
Repeated crush injuries of the sciatic nerve were inflicted on adult rats at 1-week intervals,  and functionality of the sciatic nerve was assessed by the static sciatic index each week for 8 weeks after the final injury. To determine the effects of repeated crush injuries on motor functional recovery of the sciatic nerve, tibialis anterior muscle fibers from single and triple crush  injuries were examined, and fiber size and fiber reinnervation during the 2- to 4-week period after the final injury were measured.


RESULTS
Compared to single crush injuries, which completely recovered by post-injury week 4, double crush injuries resulted in retarded, but complete  recovery by post-injury week 6, whereas triple crush injuries resulted in marked retardation in the regenerative process with incomplete recovery during week 8 of the experimental period. Muscle fiber size for rats with triple crush did not recover to normal range at post-injury week 4, despite  its normal size for rats with single crush. The rate of reinnervation increased prominently between post-injury weeks 2 and 3 in both injuries, but the rate with triple crush was lower than that with single crush at post-injury week 3.


CONCLUSIONS
These results, which contradict  those of a previous study that reported early functional recovery, indicate that repeated crush injuries inhibit motor functional recovery of the damaged sciatic nerve, as evidenced by delayed and incomplete regeneration, atrophied muscle fibers, and delayed reinnervation.
Shinshu University School of Medicine, Matsumoto, Japan.
Toshiro
T
Itsubo
Nanae
N
Fukushima
Akira
A
Kakegawa
Kumiko
K
Yokouchi
Kyutaro
K
Kawagishi
Hiroyuki
H
Kato
Tetsuji
T
Moriizumi
D000704:Analysis of Variance; D000818:Animals; D002038:Bungarotoxins / Q000493:pharmacokinetics; D004195:Disease Models, Animal; D005260:Female; D009069:Movement Disorders / Q000209:etiology*; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000473:pathology; D009409:Nerve Crush / Q000379:methods*; D009469:Neuromuscular Junction / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function / Q000502:physiology*; D020426:Sciatic Neuropathy / Q000150:complications* / Q000473:pathology; D016708:Synaptophysin / Q000378:metabolism; D013997:Time Factors
D002038:Bungarotoxins; D016708:Synaptophysin