Applied Anatomy Of Adult Optic Canal And Its Associated Structures

Objective To study the optic canal and its associated structures such as orbital region and surrounding areas before clinoid to provide anatomical basis for the transcranial decompression of optic nerve. According to the results obtained in the Institute of Anatomy, summarize the surgical techniques and precautions of transcranial optic nerve decompression. Explore the best surgical option when traumatic optic neuropathy.Methods10 randomly selected no abnormal appearance of formalin fixed adult cadaveric heads,sawed the skull and the dura mater incision to the brain according to the occipital protuberance on the upper edge of the eyebrow 1 cm connection, to observe and measure the optic canal and its related structures such as Orbital region and surrounding areas before clinoid under a microscope from December 2014 to March 2015. Then select five adult stem skulls, randomly, worn out bone structure surrounding the optic canal, grind cranial orifice, middle part, orbital orifice of the optic cana to orbital plane of the longitudinal axis of the optic canal, measure the diameter and vertical diameter.Results1. The angle between the optic canal cranial sagittal and axial plane is(36.30 ± 3.27) °,and the angle between the optic canal cranial sagittal and coronal plane is(21.32 ±3.42) °. The transverse areas in cranial orifice, middle part, orbital orifice of the optic canal are(19.22±4.58),(18.26±4.33),(21.08±3.96) mm2, respectively; The distance from endocranial opening of optic canal to glabella is(63.88±4.63) mm, and the range from endocranial opening to pterion is(51.97±2.98) mm.The distance from orbital opening of optic canal to glabella is(63.88±4.63) mm, and the range from orbital opening to pterion is(51.97±2.98) mm.2. The total length of the anterior clinoid process is(9.52±0.38) mm, width of its root is(11.45±0.67) mm. The ratio of anterior clinoid gasification is 20%. Anterior clinoid process is close to cranial nerve and internal carotid artery.3. 12 side falciform ligament with a sharp sickle ligament trailing edge in this group press optic nerve. Falciform ligament, annular tendon and the region dura are relatively tough and firm, and no significant space between them and the optic nerve.4. Three trochlear nerves(15%) in this group pulled by posterior ethmoidal arteries,causing them to close to superior rectus tendons.5. The transverse areas in cranial orifice, middle part, orbital orifice of the optic nerve are(10.74±2.48),(9.26±2.23),(8.48±1.96)mm2, respectively.6. The ophthalmic artery goes beneath the optic nerve when it is in the optic canal. Most of the ophthalmic artery trave from below within the optic nerve in cranial orifice, to the outside bottom of the optic nerve in orbital orifice. Most of the optic sheath artery located beneath the optic nerve or the outer optic nerve.Conclusion1. The upper wall and the outer wall of the optic canal should be full cut when choosing transcranial optic nerve decompression.2. It can reduce the chance of damage to cranial nerve and internal carotid artery by grinding anterior clinoid process correctly.3. The method to incise falciform ligament and the dura vertically on the optic nerve,and to slit annular tendon close to the inside when near the orbital orifice, can depressurize optic nerve effectively, And it also can reduce the chance of damage to the trochlear nerve, avoid damage to the ophthalmic artery and optic sheath artery.4. The transpterional approach is the classic surgical of traumatic optic canal decompression, worthy of promotion.