| ObjectiveMeeting the needs of the clinical application, we learned the anatomic landmarks and the variations related to the operation of transethmoidal-sphenoid neuroendoscopic optic canal decompression, via both the anatomic and radiographic study, and we also measured the anatomical data associated with this approach to confirm the margin of safety during the operation. Further more, the study explored the new methods to orient the optic canal with the expectation of improving the accuracy and safety of endoscopic optic canal decompression. The maximum effective drilling ranges of the medial wall of optic canal were also measured to evaluate its effectiveness from an anatomical standpoint. And the study also discussed the advantages of the approach and explored the impact of prognostic factors related to the operation combine with the retrospective analysis of clinical cases.Materials and MethodsSection Ⅰ:1. Three dimensional CT scan and reconstruction of the optic canal were performed respectively on six (Twelve sides) dry cadaver heads of Chinese adults which were selected randomizely, and related anatomic parameters were measured on CT images. The diameter and the cross-sectional area of the orbital opening, cranial opening and middle of the optic canal were calculated with the formula respectively. Then the heads were cut along the line linked by the point 10mm up to the bilateral eyebrow arch and the external occipital protuberance, the relative skull base structures were observed and the distance of the orbital opening, cranial opening and middle of bilateral optic canal were measured. And then, the heads were cut along the line of the middle axial and the brain tissues were removed. The relative structures were anatomised ccording to the pathway of the transethmoidal-sphenoid neuroendoscopic optic canal decompression. The anatomic landmarks were sought and confirmed along the approach, the distance between the anatomic landmarks and the length of the medial wall of optic canal were measured. The two sets of data which were obtained by using CT images and entity anatomy were compared.2. Simulated surgery of transethmoidal-sphenoid neuroendoscopic optic canal decompression with assist from rigid neuroendoscope was performed on six damp cadaver heads of Chinese adults (Twelve sides) which were fixed by formalin, and whose arteries were perfused with red latex before the surgery. The anatomic landmarks on the posterior and lateral walls of the sphenoid sinus were observed and recorded, and the positional relation between the cranial opening of optic canal and the center point of the tubercular recess were confirmed. The bony structures of the posterior and lateral walls of the sphenoid sinus were milled to explore the maximum effective drilling ranges of the medial wall of optic canal and observe the relationship between the optic nerve and the internal carotid artery. The distances from the vertex of the internal carotid siphon to the middle line were measured. At last, the optic sheath were incised to observed the distributions of the ophthalmic artery, and the positional relations between the optic nerve and the ophthalmic artery in orbital opening, cranial opening and middle of the optic canal were recorded.Section Ⅱ:Retrospectively analyzed the total of 4 cases (5 eyes) of traumatic optic neuropathy patients who went transethmoidal-sphenoid neuroendoscopic optic canal decompression in our hospital. The operation time, intraoperative blood loss and postoperative complications were recorded. And the visual acuity before and after surgery of all the patients were recorded and compared. The advantage of the approach and the impact of prognostic factors related to the operation were explored combined with the foundation of the anatomical study and literature review.ResultsSection I:1. By comparison, there is no significant difference between the two sets of data of the distances of the orbital opening, cranial opening and middle of bilateral optic canal and the length of the medial wall of optic canal which were measured by using CT images and entity anatomy. The diameter of the orbital opening, cranial opening and middle of the optic canal were (16.42±1.56)mm、(17.32±1.60)mm and (13.58±1.42)mm, and the cross-sectional area were (18.42±2.17)mm2、(22.64±2.23)mm2 and (15.12±2.05)mm2. The distance between the columella nasi and the orbital opening, cranial opening and middle of optic canal, anterior ethmoidal foramen, posterior ethmoidal foramen and the crossing points between the anterior wall of sphenoid sinus and the cribriform roof were (61.95±5.42)mm、(68.18±5.77)mm、(66.72 ±4.87)mm、(58.09±5.03)mm、(59.31±4.96)mm and (60.12±5.01)Hmm.The distance hetween the posterior ethmoidal foramen and the anterior ethmoidal foramen, the crossing points between the anterior wall of sphenoid sinus and the cribriform roof, the orbital opening, cranial opening and middle of the optic canal were (16.2±2.51)mm, (4.32±1.14)mm、(5.76±1.68)mm、(6.85 ±1.73)mm and (6.35±1.54)mm. The maximum effective drilling ranges of the medial wall of optic canal in orbital opening, cranial opening and middle of the optic canal were (7.82± 2.63)mm、(8.05±2.77)mm and (6.92±2.01)mm.2. The occurrence rate of the optic protuberance, carotid protuberance, medial opticocarotid recess and the lateral opticocarotid recess were 83.3%(Ten sides),91.7%(Eleven sides),58.3%(Seven sides) and 75.0%(Nine sides), while occurrence rate of the tubercular recess and sellar floor were both 100%(Six cases). On the coordinate system with the origin at the center point of the tubercular recess, the horizontal and the vertical coordinate of the cranial opening of the optic canal were (1.11+ 0.12)mm and (0.37±0.06)mm, and as calculated, the angle between the line linked by the center point of the tubercular recess and the cranial opening of the optic canal with the horizontal coordinate was (17.23±1.34)°. The distances from the vertex of the internal carotid siphon to the middle line was (1.12±0.13)mm. At the cranial opening of the optic canal,75.0%(Nine sides) of ophthalmic arteries were medial-inferior to the optic never, and 25.0%(3 sides) were inferior to the optic never, while at the orbital opening of the optic canal,16.7%(Two sides) of ophthalmic arteries were inferior to the optic never, and 83.3%(Ten sides) were lateral-inferior to the optic never.Section Ⅱ:Unilateral operation takes an average of 90 min (78～90 min), intraoperative hemorrhage 80 ml (70～100 ml), there were no postoperative complications such as bleeding, infection, and cerebrospinal fluid leakage.4 cases (5 eyes) of postoperative total effective rate was 60%(3/5), Patients with preoperative residual vision, regardless of the length of the course of the disease, the improvement of visual acuity to some extent, whereas patients with preoperative dull sense of no increase.ConclusionSection I:The operation of endoscopic transethmoidal-sphenoid optic canal decompression is a kind of minimally invasive surgery with direct approach and exact effect. Fully grasp the relevant local anatomical structure and depth ranges are important prerequisites to ensure the safety of surgery. Reading the CT images and making the related measurement preoperatively, combined with a variety of positioning methods can improve the accuracy of surgery.Section Ⅱ:Optic canal decompression has a positive impact for part of the traumatic optic neuropathy patients, and endoscopic transethmoidal-sphenoid approach to optic canal is suitable for clinical promotion due to the direct path, few complications snd easy to operate. |
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