gms | German Medical Science

Aim/methods: The aim of this study was to analyse the effect of irradiation on the facial nerve. X-rays were applied in daily fractions of 2 Gy to the left neck and cheek region of 54 female Wistar rats (total dose: 60 Gy) in an experimental model with half-side exposure of the neck to the radiation source. Groups of animals were sacrificed at different times after irradiation and biopsy samples of the masseter muscle with adjacent facial nerve segments were immersion-fixed in glutaraldehyde. Semi-thin sections were stained with toluidine blue and investigated morphometrically using an integrated imaging system and standard computer software. The facial nerve of the shielded right side served as internal control and was inves-tigated in order to reveal possible scattering effects of irradiation. Facial nerves of non-irradiated rats served as external controls.

Results: Morphometric analysis revealed spatial and temporal effects of irradiation on the axon and myelin sheath. By 3–4 months after irra-diation the area of the axon had increased relative to the total area of the nerve fibre. After 9 months both the myelin sheath and the axon were diminished in diameter, the myelin sheath more so than the axon. Scattering effects of irradiation also became evident.

Conclusion: This study demonstrated early and late effects of irradiation on peripheral nerves. These experimental findings could have a bearing on the long-term follow-up of patients with a history of radiotherapy for head and neck cancer who display neurological deficits.