Applied anatomy of the optic chiasma and its surrounding structures related with sellar tumour and its clinical significance

Objective:To provide morphological evidences for the reasons of the visual field defect caused by the optic chiasm compressing through saddle area tumors. Methods: 80 adult cadaveric heads were dissected. The shape and position of the optic chiasma and its relationship with saddle diaphragm, pituitary, internal carotid artery and the tiny arteries of optic chiasma were studied. Results: The maximum angle of anterior horn of the optic chiasma was 100°, and the type of prechiasmatic space was predominant. The minimum angle was about 40°, and the type of postfixed predominant. The area of optic chiasma was 13.2±0.40 mm2 averagely, the thickness of saddle diaphragm 0.58±0.09 mm. For samples, 5% absent saddle diaphragm. 52.5% foramen of saddle diaphragm pushed into the opposite side, and their maximum diameter was about 7.8×9.8mm. The pituitary located inferiorly to the saddle diaphragm foramen was 52.5%. For 88% samples, the internal carotid artery touched the optic chiasma. Conclusions: The shape and position relationship of the optic chiasma, and its surrounding structures is useful for explaining the reasons of the visual field defect caused by compression from saddle area tumors.