Anatomic study of the prechiasmatic sulcus and its surgical implications

To address a lack of anatomical descriptions in the literature regarding the prechiasmatic sulcus, we conducted an anatomical study of this sulcal region and discuss its clinical relevance to cranial base surgery. Our systematic morphometric analysis includes the variable types of chiasmatic sulcus and a classification schema that has surgical implications. We examined the sulcal region in 100 dry skulls; bony relationships measured included the interoptic distance, sulcal length/width, planum sphenoidale length, and sulcal angle. The varied anatomy of the prechiasmatic sulcii was classified as four types in combinations of wide to narrow, steep to flat. Its anterior border is the limbus sphenoidale at the posterior aspect of the planum sphenoidale. The sulcus extends posteriorly to the tuberculum sellae and laterally to the posteromedial aspect of each optic strut. Averages included an interoptic distance (19.3 +/- 2.4 mm), sulcal length (7.45 +/- 1.27 mm), planum sphenoidale length (19 +/- 2.35 mm), and sulcal angle (31 +/- 14.2 degrees). Eighteen percent of skulls had a chiasmatic ridge, a bony projection over the chiasmatic sulcus. The four types of prechiasmatic sulcus in our classification hold potential surgical relevance. Near the chiasmatic ridge, meningiomas may be hidden from the surgeon's view during a subfrontal or pterional approach. Preoperative evaluation by thin-cut CT scans of this region can help detect this ridge.