End-to-side hypoglossal-facial coaptation with a "Y" tube conduit after minimal damage with the epineural window of hypoglossal nerve: Combine analyses of the vibrisseal function, collateral axonal sprouting and poliinnervation pattern of motor endplates

Peripheral nerves may be damaged due to variety traumatic conditions. In these cases requiring surgery, functional recovery is suboptimal. Various surgical repair methods have been used in order to repair the facial nerve injury. Hypoglossal-facial nerve neurorraphy is a surgical tecnique when the facial nerve stump is not accessible. In our study, we performed terminolateral hypoglossal-facial coaptation with "Y" tube conduit after facial nerve injury. We investigated the effect of the collateral sprouting at the lesion site, vibrisseal motor performans, muscle innervation and tongue muscle performance. Fourty eight adult female and twenty four male (for the "Y" tubes) wistar rat were used. As surgical procedure, Y tube HFA and end-to-side Y tube HFA were applied. In the Y tube HFA group, proximal stump of the hypoglossal nerve were cut and sutured into the long arm of a Y tube. Zygomatic and buccal facial branches were entubulated and sutured into the short arms of the Y tube. In the end-to side coaptation, epineurial window was opened to the hypoglossal nerve. This nerve were damaged minimum level (30% fiber approximately) and sutured into the long arm of the Y tube. Zygomatic and buccal facial branches were entubulated and sutured into the short arms of the Y tube. We determined collateral sprouting in the Y tube HFA group and ETS HFA group as %13 ± 1, %3 ± 1 respectively. We determined statistically significant differences between each groups. Determining LLS muscle, we observed poli-innervated motor endplates each groups ( %23±5 in the Y tube HFA group and %22±4 ETS HFA group). We didn't determined significant differences in the poli-innervation pattern. Analysis of the vibrisseal motor performance showed functional impairment. The evaluation of the tongua muscle performance analysis revealed the 41±6 and 6± 4 degrees deviation of the tongue in in the Y tube HFA and ETS HFA group, respectively. In this study, collateral axonal sprouting at the lesion site were reduced by end-to-side caoptation. However, it didn't improve functional outcome. Hypoglossal nerve injury by creating epineural window caused moderate functional deficit in the tongue muscle functions. Although collateral axonal sprouting were reduced with this technique, it did not lead to functinal recovery. We think that it is necessary the elucidation of the underlying mechanism for the functional recovery and discovering new surgical methods in future studies.