Chiasmatic Ridge: Incidence, Classification, and Clinical Implications.

Abstract

The study aimed to identify the chiasmatic ridge (CR) morphology and to discuss its surgical significance. The suprasellar region of 90 adult dry skulls with unknown ages, sexes, or nationalities was examined to record the shape and incidence of the CR. The CR was found in 14 (15.56%) of 90 dry skulls. The ridge was classified into 3 types, taking into account its shape, incidence (presence/absence), and the risk of residual tumor formation. The absence of the CR was named as Type 1 (76 cases, 84.44%). The bony extension without a hidden area was identified as Type 2 (8 cases, 8.89%), while the bony extension with a hidden area as Type 3 (6 cases, 6.67%). Type 3 CR (which has an evident hidden area beneath the ridge) should be taken into account by neurosurgeons to eliminate possible residual tumor risk during removal of tumors (eg, meningioma) with subfrontal or supraorbital approaches.