Lasers in Medical Science

, Volume 27, Issue 2, pp 479–486 | Cite as

Functional and morphometric differences between the early and delayed use of phototherapy in crushed median nerves of rats

  • Ana Paula SantosEmail author
  • Carla Adelino Suaid
  • Murilo Xavier
  • Fernanda Yamane
Original Article


This study evaluated the functional and quantitative differences between the early and delayed use of phototherapy in crushed median nerves. After a crush injury, low-level laser therapy (GaAs) was applied transcutaneously at the injury site, 3 min daily, with a frequency of five treatments per week for 2 weeks. In the early group, the first laser treatment started immediately after surgery, and in the delayed group, after 7 days. The grasping test was used for functional evaluation of the median nerve, before, 10, and 21 days after surgery, when the rats were killed. Three segments of the median nerve were analyzed histomorphometrically by light microscopy and computer analysis. The following features were observed: myelinated fiber and axon diameters, myelin sheath area, g-ratio, density and number of myelinated fibers, and area and number of capillaries. In the proximal segment (site of crush), the nerves of animals submitted to early and delayed treatment showed myelinated fiber diameter and myelin sheath area significantly larger compared to the untreated group. In the distal segment, the myelin sheath area was significantly smaller in the untreated animals compared to the delayed group. The untreated, early, and delayed groups presented a 50, 57, and 81% degree of functional recovery, respectively, at 21 days after injury, with a significant difference between the untreated and delayed groups. The results suggest that the nerves irradiated with low-power laser exhibit myelinated fibers of greater diameter and a better recovery of function.


Median nerve Crush injury Morphometry Grasping test Low-power laser 



The authors thank Prof. Amilton Antunes Barreira, Department of Neurology, and Prof. Haylton Jorge Suaid, Department of Surgery and Anatomy, University of São Paulo, Ribeirão Preto for permission to use the laboratory of facilities and equipment, Mr. Antonio Renato Meirelles e Silva for technical assistance, and Mr. Geraldo Cássio dos Reis for the statistical analysis. This study was supported by CAPES, FAPESP, and FAEPA.


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Copyright information

© Springer-Verlag London Ltd 2011

Authors and Affiliations

  • Ana Paula Santos
    • 1
    Email author
  • Carla Adelino Suaid
    • 2
  • Murilo Xavier
    • 1
  • Fernanda Yamane
    • 3
  1. 1.Department of PhysiotherapyFederal University of Jequitinhonha and Mucuri ValleysDiamantinaBrazil
  2. 2.Department of Surgery and Anatomy, Medical School of Ribeirão PretoUniversity of São PauloRibeirão PretoBrazil
  3. 3.Department of Neuroscience, Medical School of Ribeirão PretoUniversity of São PauloRibeirão PretoBrazil

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