[Microanatomic and three-dimensional reconstruction study of lateral wall and related structures of optic canal]

To investigate the key microanatomic and radiological structures of optic canal comprehensively so as to provide anatomic parameters and procedural flows for the decompression of optic canal.

Gross observations and microscopic measurements were applied on 10 (20 sides) formalin-treated cadaveric specimens and 15 (30 sides) adult skulls. Using multislice helical CT (computed tomography)-aided three-dimensional reconstruction in combination with direct anatomic measurement, the investigators dissected, photographed, measured and analyzed the shape of optic canal and analyze its anatomic relationship with the adjoining structures.

Optic canal was formed by the superior, inferior, medial and external walls and distal proximal opening. The lateral wall of optic canal was formed by anterior clinoid process with a length of (9.87 ± 1.34) mm, a width of (11.66 ± 2.35) mm, a base thickness of (5.35 ± 1.07) mm and a middle thickness of (4.50 ± 1.06) mm. Optic strut separating the optic canal from the superior orbital fissure was located inferiorly. And the distance between the apex of anterior clinoid process and the middle of ICA (internal carotid artery) groove was (4.25 ± 2.30) mm. The CSF (cerebrospinal fluid) leakage and secondary injury of optic nerve and injury of ICA, ophthalmic artery might occur during the surgical procedures due to the variation of anterior clinoid process. The microanatomic figures and radiological measurements had a mean difference very close to each other at (0.08 - 0.48) mm. No statistical difference was found (P > 0.05).

Optic nerve, ophthalmic artery and ICA may be exposed by a high-speed drilling of the lateral wall of optic canal. The drilling dissection of lateral wall plays a vital role during a successful optic canal decompression. Radiological measurement and three-dimensional reconstruction of skull base may be of great clinical significance in lesion visualization. And it helps to make a better choice of surgical approaches. The measurements provide valuable references for surgeons and researchers.