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Douglas H. Smith, Xiao-han Chen, Akira Iwata and David I. Graham

Object. Although plaques composed of amyloid β (Aβ) have been found shortly after traumatic brain injury (TBI) in humans, the source for this Aβ has not been identified. In the present study, the authors explored the potential relationship between Aβ accumulation in damaged axons and associated Aβ plaque formation.

Methods. The authors performed an immunohistochemical analysis of paraffin-embedded sections of brain from 12 patients who died after TBI and from two control patients by using antibodies selective for Aβ peptides, amyloid precursor protein (APP), and neurofilament (NF) proteins. In nine brain-injured patients, extensive colocalizations of Aβ, APP, and NF protein were found in swollen axons. Many of these immunoreactive axonal profiles were present close to Aβ plaques or were surrounded by Aβ staining, which spread out into the tissue. Immunoreactive profiles were not found in the brains of the control patients.

Conclusions. The results of this study indicate that damaged axons can serve as a large reservoir of Aβ, which may contribute to Aβ plaque formation after TBI in humans.

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Ayato Hayashi, Masanobu Nishida, Hisakazu Seno, Masahiro Inoue, Hiroshi Iwata, Tomohiro Shirasawa, Hajime Arai, Ryoji Kayamori, Yuzo Komuro and Akira Yanai

Object

The authors have developed a technique for the treatment of facial paralysis that utilizes anastomosis of the split hypoglossal and facial nerve. Here, they document improvements in the procedure and experimental evidence supporting the approach.

Methods

They analyzed outcomes in 36 patients who underwent the procedure, all of whom had suffered from facial paralysis following the removal of large vestibular schwannomas. The average period of paralysis was 6.2 months. The authors used 5 different variations of a procedure for selecting the split nerve, including evaluation of the split nerve using recordings of evoked potentials in the tongue.

Results

Successful facial reanimation was achieved in 16 of 17 patients using the cephalad side of the split hypoglossal nerve and in 15 of 15 patients using the caudal side. The single unsuccessful case using the cephalad side of the split nerve resulted from severe infection of the cheek. Procedures using the ansa cervicalis branch yielded poor success rates (2 of 4 cases).

Some tongue atrophy was observed in all variants of the procedure, with 17 cases of minimal atrophy and 14 cases of moderate atrophy. No procedure led to severe atrophy causing functional deficits of the tongue.

Conclusions

The split hypoglossal-facial nerve anastomosis procedure consistently leads to good facial reanimation, and the use of either half of the split hypoglossal nerve results in facial reanimation and moderate tongue atrophy.