Abstract

Introduction: Commissural fibers are white matter structures that ensure the integration and coordination of information between the cerebral hemispheres. The posterior commissure, one of the phylogenetically oldest commissural fibers, plays a role in functions such as the consensual pupillary light reflex. However, the anatomy of the posterior commissure and its associated structures have been examined in a limited number of studies in the literature. This study aims to investigate the microsurgical anatomy of the posterior commissure and its related structures through white matter dissection and tractography methods.

Materials and Methods: In this study, white matter dissections were performed on five postmortem human brain specimens prepared according to the method proposed by Klingler. The dissections were conducted under a microscope using microsurgical techniques and documented using three-dimensional photography. The results of the posterior commissure white matter fiber dissection were compared with the deterministic tractography findings obtained from a template incorporating diffusion data from 1,065 subjects.

Results: The dissections revealed that the posterior commissure is in close anatomical proximity to structures such as the corpora quadrigemina, pineal gland, habenular commissure, and stria medullaris thalami. It was observed that the fibers are continuous with the superior colliculus inferiorly and with the habenular commissure posteriorly. Tractography analyses demonstrated that the fibers of the posterior commissure are connected with the thalamus, tectal region, superior colliculus, brainstem, and cerebellum.

Discussion: The posterior commissure is not limited solely to pupillary reflexes; rather, it is part of a broader functional network through its connections with the brainstem and cerebellum. These fibers are also associated with the pretectal region and various mesencephalic nuclei, participating in a wide range of functions from light reflexes to vestibular system integration. Our study is one of the rare anatomical investigations that comprehensively elucidates both the anatomical and functional aspects of the posterior commissure.

Keywords: posterior commissure, commissural pathways, fiber dissection, diffusion tensor imaging

References

  1. Rhoton Jr AL. The cerebrum. Neurosurgery 2007; 61. https://doi.org/10.1227/01.NEU.0000255490.88321.CE
  2. Schmahmann J, Pandya D. Fiber pathways of the brain. New York: Oxford University Press; 2006. https://doi.org/10.1093/acprof:oso/9780195104233.001.0001
  3. Ozdemir NG. The anatomy of the posterior commissure. Turkish Neurosurgery 2015; 25(6): 837-843. https://doi.org/10.5137/1019-5149.JTN.12122-14.2
  4. Clarke E, O'Malley CD. The human brain and spinal cord: a historical study illustrated by writings from antiquity to the twentieth century. San Francisco: Norman Publishing; 1996.
  5. Nieuwenhuys R, Voogd J, Van Huijzen C. The human central nervous system: a synopsis and atlas. Springer Science & Business Media; 2007. https://doi.org/10.1007/978-3-540-34686-9
  6. Klingler J. Erleichterung der makrokopischen Präparation des Gehirns durch den Gefrierprozess. Orell Füssli; 1935.
  7. Agrawal A, Kapfhammer JP, Kress A, et al. Josef Klingler's models of white matter tracts: influences on neuroanatomy, neurosurgery, and neuroimaging. Neurosurgery 2011; 69: 238-252. https://doi.org/10.1227/NEU.0b013e318214ab79
  8. Shimizu S, Tanaka R, Rhoton AL, et al. Anatomic dissection and classic three-dimensional documentation: a unit of education for neurosurgical anatomy revisited. Neurosurgery 2006; 58: E1000. https://doi.org/10.1227/01.NEU.0000210247.37628.43
  9. Yeh FC, Tseng WYI. NTU-90: a high angular resolution brain atlas constructed by q-space diffeomorphic reconstruction. Neuroimage 2011; 58: 91-99. https://doi.org/10.1016/j.neuroimage.2011.06.021
  10. Yeh FC, Wedeen VJ, Tseng WYI. Generalized q-sampling imaging. IEEE Trans Med Imaging 2010; 29: 1626-1635. https://doi.org/10.1109/TMI.2010.2045126
  11. Yeh FC, Panesar S, Fernandes D, et al. Population-averaged atlas of the macroscale human structural connectome and its network topology. Neuroimage 2018; 178: 57-68. https://doi.org/10.1016/j.neuroimage.2018.05.027
  12. Keene ML. The connexions of the posterior commissure: a study of its development and myelination in the human foetus and young infant, of its phylogenetic development, and of degenerative changes resulting from certain experimental lesions. Journal of Anatomy 1938; 72(Pt 4): 488-501.
  13. Young MJ, Lund RD. The anatomical substrates subserving the pupillary light reflex in rats: origin of the consensual pupillary response. Neuroscience 1994; 62: 481-496. https://doi.org/10.1016/0306-4522(94)90381-6
  14. Gilbert TT, Olopade FE, Ladagu AD, et al. Microscopic anatomy of the subcommissural organ in the brain of the adult greater cane rat (Rodentia: Thryonomyidae). Anat Histol Embryol 2024; 53: e12990. https://doi.org/10.1111/ahe.12990
  15. Ortloff AR, Vío K, Guerra M, et al. Role of the subcommissural organ in the pathogenesis of congenital hydrocephalus in the HTx rat. Cell Tissue Res 2013; 352: 707-725. https://doi.org/10.1007/s00441-013-1615-9
  16. Grondona JM, Hoyo-Becerra C, Visser R, Fernández-Llebrez P, López-Ávalos MD. The subcommissural organ and the development of the posterior commissure. Int Rev Cell Mol Biol 2012; 296: 63-137. https://doi.org/10.1016/B978-0-12-394307-1.00002-3
  17. Corales LG, Inada H, Hiraoka K, et al. The subcommissural organ maintains features of neuroepithelial cells in the adult mouse. J Anat 2022; 241: 820-830. https://doi.org/10.1111/joa.13709
  18. Rhoton AL. Tentorial incisura. Neurosurgery 2000; 47: S131-S153. https://doi.org/10.1097/00006123-200009001-00015
  19. Rhoton Jr AL. The posterior cranial fossa: microsurgical anatomy and surgical approaches. Neurosurgery 2000; 47(suppl_3): S5-S6. https://doi.org/10.1097/00006123-200009001-00005
  20. Jouvet A, Fauchon F, Liberski P, et al. Papillary tumor of the pineal region. Am J Surg Pathol 2003; 27: 505-512. https://doi.org/10.1097/00000478-200304000-00011
  21. Kennedy G, Degueure A, Dai M, Cuevas-Ocampo A, Arevalo O, Cuevas-Ocampo AK. An unusual finding: papillary tumor of the pineal region. Cureus 2023; 15(2): e34725. https://doi.org/10.7759/cureus.34725
  22. Vilela-Filho O, Freitas ELA, Goulart LC, Lino-Filho AM, Carneiro R, Fernandes-Santos B. 7T magnetic resonance imaging probabilistic tractography-based evidence of decussation of the fibers between the lateral geniculate nucleus and the primary visual area. World Neurosurg 2024; 188: e555-e560. https://doi.org/10.1016/j.wneu.2024.05.152
  23. Dauleac C, Mertens P, Frindel C, Jacquesson T, Cotton F. Atlas-guided brain projection tracts: from regions of interest to tractography 3D rendering. J Anat 2025; 246: 732-744. https://doi.org/10.1111/joa.14120

Copyright and license

Copyright © 2025 The Author(s). This is an open access article distributed under the Creative Commons Attribution License (CC BY), which permits unrestricted use, distribution, and reproduction in any medium or format, provided the original work is properly cited.

How to cite

1.
Barut O, Erbaş MA, Baydın ŞS. Microsurgical anatomy of the posterior commissure. Sinir Sistemi Cerrahisi Derg 2025;10(1):10-18. https://doi.org/10.54306/sscd.2025.215