Can the angle between optic nerves indicate whether optic chiasm is prefixed, normofixed or postfixed? An anatomical study with radiologic and neurosurgical implications

Abstract

The INA is wider when OC is prefixed, intermediate when normofixed and narrowed when postfixed. This observation throws light on the possibility of using INA as a marker of RAPL of OC. As INA can be measured in axial MRI sections, it can be used in differentiation of the cases with prefixed OC from others during pre-operative work up for pituitary surgeries and to identify individuals 'at risk' during subfrontal approach for pituitary lesions.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Endoscopic Endonasal Approach to the Sellar and Parasellar Regions

“…A prefixed chiasm limits the access to suprachiasmatic corridor and a postfixed chiasm may restrict access to retrochiasmatic area. 45,46 EEA access to the cavernous sinus encounters the ICA medially as opposed to their intracranial counterpart approaches. Anteriorly, the cavernous sinuses extend to the SOF and anterior clinoid process, and posteroinferiorly they extend toward the petrous apex.…”

“…A prefixed chiasm limits the access to suprachiasmatic corridor and a postfixed chiasm may restrict access to retrochiasmatic area. 45 46…”