[Histomorphologic findings in the facial nerve after water-jet dissection of the parotid gland in dogs]. / Einflüsse des Wasserstrahljets auf die Histomorphometrie und Funktion des N. facialis.

BACKGROUND: Initial results on the application of the water-jet in a parotidectomy setting in an animal study demonstrate that there are morphologic changes which do, and some which do not, affect the clinial function of the facial nerve due to the different jet sizes and operating pressures used. In a further study the histomorphometric data of the facial nerve dissected by the water-jet should be evaluated and correlated to the different sizes of jet and operating pressures. MATERIAL AND METHODS: In total, 102 nerves (in 14 beagles) which had been dissected by water-jets of different sizes and operating pressures were evaluated. After an observation period of 21 days, including documentation of the clinical function of the facial nerve, the nerves were dissected. The number of nerve fibers and the diameter of the different nerve fibers were then evaluated. RESULTS: All nerve fibers dissected with jet sizes of 120 and 150 µm showed an identical cumulative frequency of fiber diameters. All nerve fibers dissected with a water-jet of 200 µm showed morphologic and clinical abnormalities and--in terms of nerve fiber diameters--clear differences to the nerve fibers dissected with 120- or 150-µm jets. Altogether, there is a decrease in fiber diameter along the nerve course. CONCLUSION: Our data show a shift of larger diameters of the nerve trunk to smaller diameters in the terminal nerve fibers. This phenomenon has not been described in the literature to date and is probably not due to the water-jet. Additionally, our data show that 22% of the original nerve fiber damaged by the water-jet is sufficient to preserve the nerve's clinical function.

[Histomorphologic findings in the facial nerve after waterjet dissection of the parotid gland. Animal studies in dogs]. / Einfluss des Wasserstrahldissektors auf die Morphologie des N. facialis. Tierexperimentelle Untersuchungen am Hund.

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 µm) 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 µm jet there is regularly facial nerve damage.