Endoscopic endonasal anterior clinoidectomy: surgical anatomy, technique nuance, and case series

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Advances in endoscopic technique allow for resection of the anterior clinoid process (ACP) via an endoscopic endonasal approach. The authors discuss the endoscopic endonasal anterior clinoidectomy (EEAC) and demonstrate the relevant surgical anatomy and technical nuances. The approach was simulated in 6 cadaveric heads. From a technical point of view, the lateral optic carotid recess was used as the landmark in the proposed technique. The superomedial, superolateral, and inferior vertices of this recess are the main operative points. The EEAC approach was achieved by disconnecting the ACP tip from the base by drilling the 3 vertices. The proposed approach was successfully performed in all cadaveric specimens. Then, in a case series involving 6 patients in whom the EEAC approach was used, there were no vascular injuries; 2 patients had postoperative oculomotor nerve palsy, which improved in one and resolved in the other by 1 month.

The EEAC approach for tumors and vascular lesions in the parasellar region is technically feasible. The surgical corridor is increased by ACP resection, although to a lesser extent than the transcranial anterior clinoidectomy. Based on the authors’ initial anatomical and surgical results, resection of the ACP via the endonasal endoscopic approach is a novel technique worth exploring in suitable cases.

ABBREVIATIONS ACP = anterior clinoid process; EEAC = endoscopic endonasal anterior clinoidectomy; ICA = internal carotid artery; LOCR = lateral opticocarotid recess.

Article Information

Correspondence Tao Hong: The First Affiliated Hospital of Nanchang University, Nanchang City, Jiangxi Province, People’s Republic of China. ht2000@vip.sina.com.

INCLUDE WHEN CITING Published online July 5, 2019; DOI: 10.3171/2019.4.JNS183213.

L.X. and S.X. share first authorship of this work.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    Related anatomical structures in EEAC performed on the right side of a cadaveric specimen. A: Microscopic view of the anatomical structures surrounding the ACP before anterior clinoidectomy. A1: The triangle delineating the LOCR and the 3 numbered circles indicate the 3 vertices of drilling. B: Corresponding microscopic view of the initial drilling of the LOCR. B1: First superomedial vertex drilling of the LOCR under endoscopic view. C: Corresponding microscopic view of the second drilling of the LOCR. C1: Second superolateral vertex drilling of the LOCR. D: Corresponding microscopic view of the third drilling of the LOCR. D1: Third inferior vertex drilling of the triangle-shaped LOCR. E: Microscopic view after final drilling of the ACP tip. E1: The ACP tip is removed under endoscopic visualization. F: Microsurgical view after ACP resection. F1: The ICA bifurcation and the M1 and A1 segments are identified through the corridor created by ACP resection. Cav.Sin = cavernous sinus; du.env = dural envelope; LSW = lesser sphenoid wing; O.C = optic canal; Ocul.N = oculomotor nerve; Optic.N = optic nerve; P.com = posterior communicating artery. Figure is available in color online only.

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    Case 1. Radiological images and intraoperative photographs of a recurrent ACP meningioma. A–C: Preoperative Gd-enhanced MR images showing a right ACP meningioma. D: Endoscopic view of the LOCR after sphenoidotomy. E: Separation of the medial part of the tumor. F: The lateral border of the tumor is hidden by the ACP. G: The removed portion of the ACP tip. H and I: Endoscopic view of the relevant structures after tumor resection. J–L: Postoperative MR images demonstrating complete tumor removal. L.ON = left optic nerve; P.S = pituitary stalk; R.ON = right optic nerve. Figure is available in color online only.

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    Case 2. Radiological images and intraoperative photographs of a right ACP/orbital lesion. A and B: Preoperative Gd-enhanced axial and coronal MR images showing the lesion involving the ACP and orbit. C: Sagittal MR image of the lesion. The white arrow indicates the tumor infiltrating the sphenoid sinus. D: Preoperative CT scan showing the tumor infiltrating the sphenoid sinus. The white arrow indicates the ACP. E: Endoscopic view after sphenoidotomy. F: Identification of the LOCR after removal of a portion of the tumor. G: Endoscopic anterior clinoidectomy. H: Separation of the tumor from the right optic nerve. I: Endoscopic view after tumor resection. J: Endoscopic view through the ACP triangle. K–M: Postoperative MR images demonstrating total tumor removal. N: Postoperative CT scan. The white circle indicates the disappearance of the ACP tip. Cav.Sin = cavernous sinus; L.Opt.C = left optic canal; ophth.A = ophthalmic artery; Sup.Hyp.a = superior hypophyseal artery. Figure is available in color online only.

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    Case 3. Radiological images and intraoperative photographs of recurrent meningioma involving the ACP and cavernous sinus. A–C: Preoperative Gd-enhanced MR images showing the tumor involving the ACP and right cavernous sinus and encasement of the ICA and M1 segment. D and E: Preoperative CT scans demonstrating the hyperplastic ACP. The arrow indicates the ACP. F: Endoscopic view after sphenoidotomy. G: Endoscopic anterior clinoidectomy. H: The hyperplastic ACP is removed. I: The compartment medial to the ICA is enlarged after ACP resection. J: The compartment lateral to the ICA is also enlarged after ACP resection. K: Endoscopic view after tumor resection. L–N: Postoperative MR images showing subtotal tumor resection. O: Postoperative CT scan showing ACP resection. The yellow circle indicates the ACP has been resected. P: Diameter of the resected ACP. Cav.ICA = cavernous segment of the ICA; IV = trochlear nerve; PCP = posterior clinoid process; P.G = pituitary gland; P.S = pituitary stalk; Tu = tumor; VI = abducens nerve. Figure is available in color online only.

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    Case 5. Multiple aneurysms clipped through the EEAC approach. A and B: Lateral view (A) and anteroposterior view (B) of digital subtraction angiograms showing an ophthalmic aneurysm (An1) and a paraclinoid aneurysm (An2). C and D: Lateral view (C) and anteroposterior view (D) of the 3D reconstruction images showing a third aneurysm (An3) located in the cavernous segment of the ICA. E: Exposure of the paraclival ICA for proximal control. F: Endoscopic view of the LOCR after a transplanum approach. G: Removal of the ACP tip. H: Endoscopic view after anterior clinoidectomy. I: Exposure of the ophthalmic aneurysm (An1). J: Exposure of the neck of the paraclinoid aneurysm (An2) through the ACP triangle (created by the EEAC). K and L: Postoperative lateral view (K) and anteroposterior view (L) of digital subtraction angiograms showing complete obliteration of An1 and An2. M and N: Lateral view (M) and anteroposterior view (N) of the 3D reconstruction images showing the unclipped third aneurysm (An3) located in the cavernous segment of the ICA. D.D.R = distal dural ring; Oph.a = ophthalmic artery; Paracliv = paraclival. Figure is available in color online only.

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    Steps of the EEAC approach. A: Identification of the LOCR. The blue triangle delineates the shape of the LOCR, and the numbered circle indicates each step of this technique. B: First step of the technique. C: Second step of the technique. D: Third step of the technique. E: Fourth step of the technique. F: Postoperative CT scan of the patient. The blue arrows indicate the aneurysm clip, and the yellow circle delineates the area where the ACP tip was removed. D.D.R = distal dural ring; P.D.R = proximal dural ring. Figure is available in color online only.

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    Artist’s illustration of the steps in the EEAC approach. A: Identification of the LOCR after sphenoidotomy. B: First step of the technique. C: Second step of the technique. D: Third step of the technique. E: Hollowing out of the ACP. F: ICA bifurcation and the M1 and A1 segments can be identified through the ACP triangle. Inf.vertex = inferior vertex; S.L.vertex = superolateral vertex; S.M.vertex = superiomedial vertex. Copyright The First Affiliated Hospital of Nanchang University. Published with permission. Figure is available in color online only.

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