Three-Dimensional Radiologic Study on Index Measurement of Endonasal Endoscopic Optic Nerve Decompression

Objective: To provide the radiologic basis for the clinical application of endonasal endoscopic optic nerve decompression (EEOND). Methods: CTA images were used to observe the optic canal (OC) and related structures of 60 patients (120 sides) with normal nasal, paranasal sinuses, OC, and other related structures. Results: Optic canal could be classified as: the canal (10 sides, 8.33%), the semicanal (25 sides, 20.83%), the impression (49 sides, 40.83%), and the nonimpression (36 sides, 30%). According to its relationships with the sinuses, OC could be further typed as: ethmoid sinus (22 sides, 18.3%), sphenoid sinus (38 sides, 31.7%), ethmoid and sphenoid sinus (60 sides, 50%). The thickness of OC medial wall is about 1.11 ± 0.24 mm at orbital mouth, 0.87 ± 0.25 mm at middle part and 1.19 ± 0.27 mm at cranial mouth. The arc length of OC bone wall which can be opened from the sinus cavity is about 7.18 ± 0.76 mm at orbital mouth, 8.27 ± 0.93 mm at middle part, and 6.98 ± 0.89 mm at cranial mouth. The length of the OC medial wall is 12.18 ± 1.35 mm. In the three-dimensional Cartesian coordinate system that origined with the last point of middle turbinate root and oriented by temporal side, front side, and superior side, the coordinates of midpoints of OC medial wall are: (3.64 ± 1.11, 8.48 ± 1.65, 23.14 ± 2.67) at orbital mouth, (0.16 ± 1.21, 3.99 ± 1.80, 24.85 ± 2.67) at middle part, and (−3.59 ± 1.22, 0.77 ± 2.13, 26.39 ± 2.68) at cranial mouth. One length unit on the axes is a millimeter. Conclusion: Computed tomography (CT) scanning technique can measure the data of the OC in EEOND. It has great guiding significance for clinical operation.

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