The**** chiasmatic groove (chiasmatic sulcus, optic groove, pre**chiasmatic sulcus)** is a transverse groove upon the superior aspect of the body of sphenoid bone ******** ******** within the middle cranial fossa. ******** It is bounded anteriorly by the sphenoidal limbus (a variably prominent ridge also representing the posterior boundary of the sphenoidal jugum ), and posteriorly by the tuberculum **sellae. The opening of each optic canal is placed at either lateral end of the chiasmatic sulcus. The optic chiasm is situated superior and quite posterior to the chiasmatic groove (and not against the groove as the name suggests). **