title: Gamma Knife irradiation-induced histopathological changes in the trigeminal nerves of rhesus monkeys.
abstract: OBJECTIVE
  The authors' goal was to observe histopathological changes in the trigeminal nerve after Gamma Knife surgery (GKS) in rhesus monkeys, and to investigate the radiobiological mechanism of GKS for primary trigeminal neuralgia. The nerve length-dosage effect of irradiation is also discussed.
  
  
  METHODS
  One of 5 rhesus monkeys randomly served as a control, and the other 4 monkeys were randomly administered a target radiation dose of 60, 70, 80, or 100 Gy (a different dose in each animal). The size of the collimator was 4 mm, and the target point was the trigeminal nerve root. In each experimental monkey, one side was exposed to single-target-point irradiation, and the contralateral side was exposed to double-target-point irradiation. After 6 months, the trigeminal nerve root was examined using light microscopy, transmission electron microscopy, and immunohistochemistry.
  
  
  RESULTS
  At each radiation dose, the damage to the nerve tissue by single-target-point irradiation was identical to that caused by double-target-point irradiation. In the trigeminal nerve tissues of the monkeys irradiated with 60 and 70 Gy, there was limited nerve demyelination and degeneration, fragmentation, or loss of axons. In the trigeminal nerve tissue of the monkey irradiated with 80 Gy, the nerve tissue showed a disordered structure. In the trigeminal nerve tissue of the monkey irradiated with 100 Gy, there was severe derangement in the structure of the nerve tissue, and extensive demyelination, fragmentation, and loss of axons.
  
  
  CONCLUSIONS
  The target doses of 60 and 70 Gy have very little impact on the structure of the trigeminal nerve. Irradiation at 80 Gy can cause partial degeneration and loss of axons and demyelination. A 100-Gy dose can cause some necrosis of neurons. Comparing the single-target-point with the double-target-point irradiation, the extent of damage to the nerve tissue is identical, and no difference in the nerve length-dosage effect was found.
authors.affiliation: Department of Neurosurgery, Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China.
authors.forename: Zhe-Feng
authors.initials: ZF
authors.lastname: Zhao
authors.forename: Li-Zhuang
authors.initials: LZ
authors.lastname: Yang
authors.forename: Chuan-Lu
authors.initials: CL
authors.lastname: Jiang
authors.forename: Yong-Ri
authors.initials: YR
authors.lastname: Zheng
authors.forename: Jin-Wei
authors.initials: JW
authors.lastname: Zhang
mesh_terms: D000344:Afferent Pathways / Q000473:pathology / Q000601:surgery; D000818:Animals; D001369:Axons / Q000473:pathology; D003711:Demyelinating Diseases / Q000473:pathology; D008253:Macaca mulatta; D008297:Male; D046529:Microscopy, Electron, Transmission; D009186:Myelin Sheath / Q000473:pathology; D009336:Necrosis; D009410:Nerve Degeneration / Q000473:pathology; D016634:Radiosurgery / Q000379:methods*; D014276:Trigeminal Nerve / Q000473:pathology* / Q000601:surgery*; D014277:Trigeminal Neuralgia / Q000473:pathology / Q000601:surgery