title: The Anatomy of the Posterior Commissure.
abstract: OBJECTIVE
  The connections of posterior commissure are defined. Its fibers mediate the consensual light reflex by interconnecting the pretectal nuclei. The fiber connections from the thalamic, pretectal, superior colliculus and the habenular nuclei are known, but they have not been shown anatomically. The present study is a fiber dissection study to define the anatomy of the posterior commissure.
  
  
  METHODS
  Twenty formalin-fixed sheep heads were used in the study. The specimens were fixed in 10% formalin solution for 3 weeks. The arachnoidal and vascular structures were removed by using a surgical microscope magnification (x6-x40) and brains were again fixed for 4 weeks at -20°C. The fiber dissections were performed at Marmara University, Rhoton Laboratory. Also, a radiological tractographic study was carried on five healthy volunteers to see the posterior commissure cortical connections.
  
  
  RESULTS
  In fifteen sheep brains, the dimensions of the posterior commissure were measured as 1.36 mm (range 0.5-2.5 mm) width, and as 4.6 mm (range 3-6 mm) length. In the dissection study, a frontotemporooccipital fascicle was observed to connect with the fibers of the posterior commissure. Diffusion tensor imaging scans showed the frontotemporooccipital tract to extend to posterior commissural region.
  
  
  CONCLUSIONS
  To our knowledge, this is the first anatomical and tractographic study regarding the posterior commissure. However, further human cadaveric studies are necessary.
authors.affiliation: İstanbul Training and Research Hospital, Neurosurgery Clinic, Istanbul, Turkey.
authors.forename: Nuriye Guzin
authors.initials: NG
authors.lastname: Ozdemir
mesh_terms: D000818:Animals; D056324:Diffusion Tensor Imaging; D006801:Humans; D009434:Neural Pathways / Q000033:anatomy & histology*; D066243:Posterior Cerebellar Commissure / Q000033:anatomy & histology*; D012756:Sheep