Silver nitrate injury in the rat sciatic nerve: a model of facial nerve injury.
BACKGROUND
An unpublished communication of a permanent facial paralysis secondary to silver nitrate application in a postoperative mastoid cavity with a dehiscent facial nerve raises concern regarding its neurotoxicity. This study was performed to examine functional neural injury and the morphology of nerve injury due to silver nitrate contact with a peripheral motor nerve.


METHODS
Sprague-Dawley male rats were assigned to a sham surgery group or to a group where silver nitrate was applied directly to a surgically exposed sciatic nerve for 1, 5, or 10 seconds. Individual walking track data were collected on postoperative days (POD) 1, 4, 7, and 14, and the Sciatic Functional Index (SFI) was calculated to assess neural function. On POD 14, the cauterized nerve was harvested, and the histologic axon loss of each specimen was graded.


RESULTS
In all experimental groups, the most severe functional loss was noted on POD 1. At POD 14 the greatest neural recovery was observed in the 1-second group, whereas the 5- and 10-second cautery groups demonstrated a significantly worse deficit. A moderate or greater degree of axon loss was observed in 50% of animals injured for 1 second and nearly all animals injured for 5 or 10 seconds.


CONCLUSIONS
Functional and neuropathologic data demonstrate that silver nitrate causes significant injury to the rat sciatic nerve. A 5-second cautery causes greater functional impairment and more severe axonal loss than a 1-second injury.
Wachter
Bryan G
BG
Departments of Otolaryngology-Head and Neck Surgery, Physiology, , Loyola University Medical Center, Maywood, Il, USA.
Leonetti
John P
JP
Lee
John M
JM
Wurster
Robert D
RD
Young
M Rita I
MR
D000818:Animals; D001369:Axons / Q000187:drug effects; D004195:Disease Models, Animal; D020220:Facial Nerve Injuries / Q000139:chemically induced*; D008297:Male; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D018570:Risk Assessment; D012307:Risk Factors; D012584:Sciatic Nerve / Q000187:drug effects* / Q000473:pathology*; D012835:Silver Nitrate / Q000009:adverse effects* / Q000494:pharmacology; D013997:Time Factors
D012835:Silver Nitrate