LAUSR

OBJECTIVE Understanding the relationship between the carotid artery, optic nerve and the anterior clinoid process is the basis of surgical approaches performed in the subchiasmal region. The location of the optic chiasm, the length of the optic nerves, and the distance and angle between the optic nerves determine the route of surgical approaches. We have determined the types of optic chiasm to study the relationship between vascular and neural structures in this region. MATERIALS AND METHODS Thirty autopsy specimens were investigated at the Bursa Forensic Medicine Institute for optic chiasm types and the relationship between the neural and vascular anatomical structures of the sellar-parasellar and subchiasmal region was examined between June 2016 and November 2016. RESULTS In this study, 4 prefix types (13%), 6 postfix types (20%), and 20 central types (67%) of chiasm were defined. Furthermore, we measured this angle between two optic nerves, which indirectly shows the location of chiasm according to the diaphragma sellae, and then detected the mean value of this angle as 87.1±11.6°. The "limit" value to designate a chiasm as prefix was measured in the current study as ≥101.1°. The angle between optic nerves ranged from a mean value of 69.9±3.7° in 6 cases with postfix chiasm, to a mean value of 104.0±2.1° in 4 cases with prefix chiasm and a mean value of 88.8±6.7° in 20 cases with central chiasm. CONCLUSION In this study, we showed that the relationship among optic chiasma types, optic nerves and bony and vascular structures around the sellar area was effective at determining the surgical approach to this region.