Impact of Anterior Clinoid Process Pneumatization on Adjacent Anatomical Structures

The Anterior clinoid process is closely related to many important anatomical structures including vessels, nerves, and paranasal sinuses. In the majority of cases, this process is osseous, but its pneumatization has been recorded as an anatomic variant. Coronal CT scans of the head region that were done for thirty-seven patients at Tanta University hospitals were collected to be used in teaching radiological anatomy for medical students. During their routine investigation, a case of a female aged 21 years showed bilateral pneumatization of the anterior clinoid processes associated with some variants of the adjacent anatomical structures. These findings were discussed on anatomical basis with referral to their possible clinical implications. If a surgical removal of the anterior clinoid process is recommended, a comprehensive knowledge of its anatomy, pneumatization, and associated regional anatomic variants is crucial for neurosurgeons to avoid risky complications.

Measurement of Critical Structures around Paraclinoidal Area : A Cadaveric Morphometric Study

OBJECTIVE: Although removal of the anterior clinoid process (ACP) is essential surgical technique, studies about quantitative measurements of the space broadening by the anterior clinoidectomy are rare. The purposes of this study are to investigate the dimension of the ACP, to quantify the improved exposure of the parasellar space after extradural anterior clinoidectomy and to measure the correlation of each structure around the paraclinoidal area. METHODS: Eleven formalin-fixed Korean adult cadaveric heads were used and frontotemporal craniotomies were done bilaterally. The length of C6 segment of the internal carotid artery on its lateral and medial side and optic nerve length were checked before and after anterior clinoidectomy. The basal width and height of the ACP were measured. The relationships among the paraclinoidal structures were assessed. The origin and projection of the ophthalmic artery (OA) were investigated. RESULTS: The mean values of intradural basal width and height of the ACP were 10.82 mm and 7.61 mm respectively. The mean length of the C6 lateral and medial side increased 49%. The mean length of optic nerve increased 97%. At the parasellar area, the lengths from the optic strut to the falciform liament, distal dural ring, origin of OA were 6.69 mm, 9.36 mm and 5.99 mm, respectively. The distance between CN III and IV was 11.06 mm. CONCLUSION: With the removal of ACP, exposure of the C6 segments and optic nerve can expand 49% and 97%, respectively. This technique should be among a surgeon's essential skills for treating lesions around the parasellar area.

Determination of Aneurysmal Location with 3 Dimension-Computed Tomographic Angiography in the Microsurgery of Paraclinoid Aneurysms

OBJECTIVE: Determining the location of paraclinoid aneurysms for microsurgery is important for selecting treatment options, especially when deciding on the release of the dural ring in direct clipping. We examined the reliability of using the optic strut as an anatomical landmark for evaluating the location of paraclinoid aneurysms. METHODS: Cadaveric dissection was performed to establish the relationship of the optic strut to the dural ring. Results from these anatomic studies were compared with the three-demensional computed tomographic angiographic (3D-CTA) findings of nine patients with ten paraclinoid aneurysms between May 2004 and October 2005. These, 3D-CTA results were then compared with intraoperative findings. RESULTS: The inferior boundary of the optic strut accurately localized the point at the proximal dural ring in cadaveric study. The optic strut and its relationship to the aneurysms was well observed on the multiplanar reformats of 3D-CTA. During microsurgery, nine of ten aneurysms were verified to arise from distal to the upper surface of the optic strut. Two aneurysms that had arisen between the inferior and superior boundary of the optic strut were observed to lie within the carotid cave. One aneurysm which had arisen at the inferior boundary of the optic strut and directed inferiorly was observed to lie within the cavernous sinus just after the release of the proximal ring. CONCLUSION: The optic strut, as identified with multiplanar reformats of 3D-CTA, provided a reliable anatomic landmark for the proximal rings and an important information about the location of aneurysms around the anterior clinoid process (ACP). Therefore, 3D-CTA and the optic strut could become an invaluable tool and a landmark in the assessment of the location of paraclinoid aneurysms for microsurgery.

Anterior clinoid process and optic strut in Koreans

The anterior clinoid process and the optic strut are often removed during operation on the anterior part of the cavernous sinus. Therefore it is important for neurosurgeons to verify their dimensions and variations. The purpose of this study was to investigate the dimension and the variation of the anterior clinoid process and to describe the locational variation of the optic strut. Seventy-three skulls of Korean adults were used. The average length, basal width and thickness of the anterior clinoid process were 9.18 +/- 1.55, 9.63 +/- 1.49 and 5.32 +/- 1.07 mm, respectively. The average thickness of the optic strut was 2.9 +/- 1.15 mm and it was commonly attached to anterior two-fifths of the anterior clinoid process. The complete caroticoclinoid canal was observed in 4.1%, however it was incomplete in 11.6%. The incidence of a caroticoclinoid canal in Koreans was relatively low compared with other races.