Objective: To select the optimal method for developing experimental animal model of viral facial paralysis by comparing several inoculation methods.
Method: One hundred and twenty Balb/c mice were divided into 4 groups, with each group having 30 mice. Group A, the posterior auricular branch of right facial nerve were incised and inoculated with 25 microl HSV-1; group B, 25 microl HSV-1 were inoculated into the posterior aspect of the right auricle by cutaneous scarification; group C, 25 microl HSV-1 were injected into subcutaneous tissue of the posterior aspect of the right auricle; group D, 100 microl HSV-1 were inoculated in the way similar to that of group C. The symmetry of mouse face was observed, and the incidence of paralysis and death were analyzed. The temporal bones of paralyzed mice were serially sectioned and stained with hematoxylin and eosin.
Result: Thirteen (43.33%) mice developed the right facial paralysis and recovered from it 3-7 days later in group A. Six (20%) mice developed the paralysis and recovered from it 2-9 days later in group B. Group C had no signs of facial paralysis and group D had 1 paralyzed animal. Except for 12 mice in group D, there was no death in the other groups. Nerve swelling was observed in right temporal facial nerve of paralyzed mice. Facial nerve to facial canal cross-sectional area ratio (FN/FC) of the right side was much higher than that of the left side.
Conclusion: Inoculating HSV-1 into the posterior auricular branch of facial nerve can produce an acute and transient facial paralysis in mice. With the advantage of higher morbidity of facial paralysis and lower mortality in comparison to the other methods, it is an optimal method.