J Korean Neurosurg Soc.  2013 Jul;54(1):14-18. 10.3340/jkns.2013.54.1.14.

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

• Lee HW
• Park HS
• Yoo KS
• Kim KU
• Song YJ

• KMID: 2190851
• DOI: http://doi.org/10.3340/jkns.2013.54.1.14

Abstract

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.

Keyword

Anterior clinoid process; Extradural anterior clinoidectomy; Optic strut; Ophthalmic segment

MeSH Terms

Adult
Cadaver
Carotid Artery, Internal
Craniotomy
Head
Humans
Ophthalmic Artery
Optic Nerve

Figure

• 

  Fig. 1 A: Measurements before anterior clinoidectomy. Exposure of the ICA and optic nerve in operative view (left) and schematic image (right). (a) and (b) represent the lengths of the exposed ICA on its lateral and medial sides, respectively. (c) is the optic nerve length from the chiasm to the falciform ligament, (d) and (e) are the intradural basal width and height of the ACP, respectively. B: Exposure of the ICA and optic nerve after anterior clinoidectomy in operative view (left) and schematic image (right). (a') and (b') represent the extended ICA length on its lateral and medial sides, respectively. They correspond to the entire C6 segment of the ICA. (c') is the optic nerve length from the chiasm to the annulus of Zinn. ACP: anterior clinoid process, OC: optic chiasm, PcomA: posterior communicating artery, ICA: internal carotid artery, DDR: distal dural ring, II: optic nerve, A1: anterior cerebral artery, M1: middle cerebral artery.

• 

  Fig. 2 Operative views (A and B) and a schematic iamge (C) after extradural anterior clinoidectomy. A: Before releasing the DDR and opening the optic sheath. The distance between the optic strut and the falciform ligament was checked (f). The distance between the lateral portion of the DDR and the optic strut was checked (g). The distance between the entry of the CN III into the cavernous sinus and the point of intersection with the CN IV was measured (h). B: Operative view after opening of the optic sheath, and releasing of the DDR. The OA was exposed and the distance between its origin and the optic strut is checked (i). DDR: distal dural ring, OA: ophthalmic artery, ICA: internal carotid artery, II: optic nerve, III: oculomotor nerve, IV: trochlear nerve, V1: ophthalmic branch of trigeminal nerve.

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