The Intersegmental Anastomosis of the Posterior Spinal Nerve Rootlets of the Thais

Objective: To demonstrate the percentages of the type as well as the frequencies of the rootlet anastomoses in all levels of the spinal cord of the Thais. Methods: Spinal cords and meninges were dissected from the vertebral columns of 42 Thai cadavers at the Department of Anatomy, Faculty of Medicine Siriraj Hospital. The dura and arachnoid maters were carefully dissected along the median plane longitudinally to expose the spinal cord posteriorly. The posterior nerve roots, rootlets and cauda equina were carefully exposed for a clear vision. Each of the spinal cords was examined throughout its length looking for posterior rootlet anastomoses. Results: The percentages of intersegmental anastomosis between posterior rootlets were 45, 3, 29 and 23% in the cervical, thoracic, lumbar and sacral segments, respectively. Three types of intersegmental anastomosis, 1a, 1b and 2 were recorded. Conclusion: Intersegmental anastomosis of the posterior nerve rootlets was observed in every segment of the spinal cord; the highest incidence was found in the cervical segment. The findings in this study suggest a variable range of dermatome distribution at a higher extent than previously thought.Â