These results suggest the crucial role of ERK in nerve regeneration but not sensory neuronal loss after trauma.

Background: In facial reanimation surgery, higher donor facial nerve axonal load yields a superior outcome. Nerves supplying the zygomaticus major muscle are primary donors for the grafting procedure; however, their topography has not been studied in detail. This study identified potential donor nerves by quantifying axon loads of the zygomaticus major muscle through histological analysis of cadaveric specimens. Materials and Methods: Forty-three hemifaces from 26 fresh human cadavers were studied. Branching patterns of nerves were classified according to their shapes. All branches of interest were sectioned and stained for an axon count. The potential donors were mapped into each tributary of nerves supplying the zygomaticus major. Results: Branching patterns were categorized into five types: Y-type (28%), X-type (28%), H-type (19%), E-type (14%), and F-type (11%). The mean number of axons in the most superiorly and proximally located main branches was 1387.33 ± 406.59 in Y-type, 1021.42 ± 187.79 in X-type, 1222.75 ± 193.82 in H-type, 1496.17 ± 364.567 in E-type, and 1353.40 ± 256.07 in F-type ( P > 0.05). A topographic relation between facial nerves supplying the zygomaticus major muscle and their mean axonal load was illustrated. The zygomatic/buccal branches were found within 5 mm from Zuker's point in 100% of X-, Y-, H-, and E-type and 75% of F-type specimens. Conclusions: Most proximal facial nerve branches supplying the zygomaticus major, arising at the anterior border of a parotid gland, contained over 900 axons in all five branching types. The primary subbranches may be used in selected cases if donor weakness is a concern. Further, our study provides evidence that demonstrates the precision of Zuker's point.

These data suggest the role of p38 in sensory neuronal loss after nerve transection. Future studies should be done to confirm the apoptotic role of p38 in this condition.

Morphometric analysis of nerve biopsy provides data of structural changes that are essential for early detection of peripheral neuropathy. Because of the laborious work associated with the total fiber quantification, various sampling methods have been introduced with controversial accuracy. Three-window sampling technique has been recently proposed to provide the accurate morphometric data of normal human sural nerve. However, its application in the diseased nerve has not been validated. This study, therefore, compared the morphometric data of nerve biopsies from 12 patients with various neuropathies obtained using this sampling method and those obtained by total fiber analysis. Total number, density, and diameter of myelinated fibers including myelin thickness and g ratio were analyzed. Intraclass correlation coefficients ranging from 0.95 to 0.99 indicate the high agreement between the data derived from the two methods in these parameters. This finding suggests the accuracy of the three-window sampling technique in the morphometric study of nerve with pathological alterations.