Electroneurography during facial nerve expansion

Effects of antineoplastic agents on the peripheral nerves under a surgical tissue expansion procedure: An experimental study

BACKGROUND

Elongation of peripheral nerve by the use of a tissue expander is helpful to repair nerve defects. This study was designed to investigate the effects of some antineoplastic agents on the peripheral nerves under a surgical tissue expansion procedure.

MATERIALS AND METHODS

Twenty-five Wistar rats were used in this study. Following the exposition of the sciatic nerve and placement of two 10/0-nylon sutures in the epineurium 20 mm apart, a tissue expander was then placed under it. Inflation of the expander was immediately accomplished by the separate percutaneous injections of 6, 6, and 8 ml for every 3 min under general anesthesia. The expander was fully deflated at the end of each 3 min The distance between two sutures was measured 1 h later to measure the rate of elongation. Rats were randomly divided into five groups (according to the administered drugs), each consisting of five rats (10 sciatic nerves). Normal saline (1 ml) in the control group (group I), cyclophosphamide (15 mg/kg) in the group II, cisplatinum (3 microg/kg) in the group III, mitomycin-C (0.5 mg/kg) in the group IV and 5-fluorouracil (10 mg/kg) in the group V were injected intravenously. Intravenous injections of drugs were performed via the tail vein 30 min before expansion, 48 and 96 h after removal of expander. The incision was reopened on the third and seventh postoperative days, and five sciatic nerves of each group were exposed and then the pinching test was performed to measure regeneration distance. Electroneurographic changes were recorded. The expanded portion of the sciatic nerve between two sutures was harvested for histological evaluation.

RESULTS

There is no significant difference between the elongation rates of all groups (P < 0.05). Histologic evaluation showed that inflammatory changes, vacuolization, intraneural edema, demyelination, axonal changes in the control group, the cisplatinum group, and the mitomycin-C group. These changes were significantly decreased in the cyclophosphamide group and the 5-fluorouracil group. In the cyclophosphamide group and the 5-fluorouracil group, the amplitude of compound action potential (CAP) values were significantly higher and the latency was significantly shorter (P > 0.05).

CONCLUSION

We believed that cyclophosphamide and 5-fluorouracil may be helpful in tissue expansion of peripheral nerves, by decreasing the effects of the ischemia-reperfusion injury on the expanded peripheral nerves.

Retrograde degeneration of the facial nerve after acute traction on parotid gland: an experimental investigation

The parotid gland of the cat underwent traction for 2 hours (group A) or until the facial nerve was broken (group B). The cats survived postoperatively for 1 day, 2 weeks, 1 month, and 3 months, respectively. Each cat underwent an electroneurography session before they were killed. The facial nerve was harvested and underwent histologic examination. The present study demonstrated that, in group A, the degree of facial nerve degeneration indicated with evoked electroneurography was 100% at 1 day and 2 weeks and 85% and 35%, respectively, at 1 and 3 months after damage. In group B, no electric response was recorded, epineurium of extratemporal segment was broken. This study also showed that the pronounced alteration of the facial nerve following acute traction on the parotid gland was retrograde degeneration; it involved up to its internal acoustic meatus segment. Furthermore, pronounced damage was noted in its stylomastoid foramen and extratemporal segment.