Histomorphologic findings in the facial nerve after waterjet dissection of the parotid gland. Animal studies in dogs

Background. The postoperative facial nerve palsy is a complication after parotidectomy which one is afraid of. The waterjet seems to be a surgical technic which allows separating different tissues without destroying important structures like vessels and nerves. Material and Methods. Totally, 106 nerve preparations, done by the waterjet of 14 beagles, were evaluated. According to a defined procedure during parotidectomy by waterjet different cones and pressure were used. After a period time of 21 days the trunk, the frontal branch and both oral branches of the facial nerve of both sides were dissected. The tissue preparation was done using the standard technic for EM-sections. Results. There are mainly changes due to the preparation like the reduction of nerve fibers and fibrosis depending which cones and pressure has been used. Conclusion. Therefore neither the size of the jet (120 or 150 mu m) nor the operating pressure of 40 to 60 or 80 bar plays an important role for the function of the facial nerve. Damage to the nerve is mainly due to the preparation technic and the application time. Using the 200 mu m jet there is regularly facial nerve damage.