Microanatomy and clinical significance of the trigones in middle skull fossa and cavernous sinus

Objective To understand the microanatomical struction of the commonly-used trigones related to the cavernous sinus (CS) and provide safe operative approaches for direct microsurgical operation on the CS. Methods 15 adult cadaver heads were used to dissect, observe and measure the regions in three CS walls under microscope. Results There were medial trigone and oculomotor nerve trigone in the superior wall of the CS. The lateromedial trigone, Parkinson trigone, Mullan trigone, Anteromedial trigone, Glasscock trigone and Kawase trigone were in the lateral wall or around. The inferolateral trigone and inferomedial trigone were in the posterior wall. Out of 10 trigones, the medial trigone and Parkinson trigone were more important than the others. Nearly all structures and spaces of CS could be exposed via those two trigones. Conclusion (1) The trigones of CS could provide safe approaches for direct exposure of CS with some important nerves and arteries protected. (2) The medial and Parkinson trigones were more often used clinically. (3) Kawase trigone forms an important passage from middle fassa to post fassa.