- Goodman Campbell Brain and Spine, Department of Neurological Surgery, Indiana University, Indianapolis, Indiana, USA
- Pediatric Neurosurgery, Children's Hospital, 1600 7th Avenue South ACC 400, Birmingham, Alabama, USA
Aaron A. Cohen-Gadol
Goodman Campbell Brain and Spine, Department of Neurological Surgery, Indiana University, Indianapolis, Indiana, USA
DOI:10.4103/2152-7806.85981Copyright: © 2011 Kulwin C. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Kulwin C, Tubbs RS, Cohen-Gadol AA. Anterior clinoidectomy: Description of an alternative hybrid method and a review of the current techniques with an emphasis on complication avoidance. Surg Neurol Int 12-Oct-2011;2:140
How to cite this URL: Kulwin C, Tubbs RS, Cohen-Gadol AA. Anterior clinoidectomy: Description of an alternative hybrid method and a review of the current techniques with an emphasis on complication avoidance. Surg Neurol Int 12-Oct-2011;2:140. Available from: http://sni.wpengine.com/surgicalint_articles/anterior-clinoidectomy-description-of-an-alternative-hybrid-method-and-a-review-of-the-current-techniques-with-an-emphasis-on-complication-avoidance/
Background:Anterior clinoidectomy is a difficult but important part of surgery for a variety of parasellar, proximal carotid and central skull base pathologies. First developed intradurally nearly 60 years ago, the promotion of an extradural technique decades later offered an approach with a different set of difficulties, risks and benefits. Many recent studies have demonstrated that there is no consensus about the “correct side” of the dura from which to remove the anterior clinoid process in a number of pathologies. Here, we review and compare the current techniques for intra- and extradural clinoidectomy and describe a hybrid alternative technique.
Methods:We used a hybrid method to potentially engage the advantages of the intradural and extradural techniques. The hybrid method starts with an extradural sphenoid wing osteotomy to the level of the superior orbital fissure (SOF). The dura is then incised parallel to the sphenoid wing lateral to the SOF, and the need for further bony removal, including clinoidectomy, is assessed after gentle elevation of the frontal lobe and release of cerebrospinal fluid through opening the optico-carotid cisterns and inspection of the pathology in relation to the clinoid. Sylvian fissure may be dissected to relieve retraction on the frontal lobe.
Results:The hybrid method allows an early identification of the optic nerve and its protection during clinoidectomy. The operator leaves the dura medial to the SOF intact and the clionoidectomy proceeds in an extradural fashion while intradural inspection periodically is performed to assess the extent of necessary extradural bony removal.
Conclusion:The hybrid method theoretically can be used as a versatile method under some circumstances. Cutting the dura along the sphenoid wing will prevent the dural layers from obscuring the clinoid and offers intradural visualization to monitor the lesion and potentially tailor bony removal.
Keywords: Clinoidectomy, complications, optic nerve, technical nuance
Anterior clinoidectomy is a technically difficult yet invaluable component of surgery for a variety of parasellar, proximal carotid and central skull base pathologies. Initially developed intradurally nearly 60 years ago,[
Anatomical benefit of clinoidectomy
The result of anterior clinoidectomy is creation of the clinoid space, the cavity previously filled by the bony process. This potential space has been well defined in microsurgical anatomical studies.[
Intradural anterior clinoidectomy
Generally, the intradural clinoidectomy begins with a standard pterional craniotomy. The dura over the lesser wing of the sphenoid may be retracted, the orbit skeletonized and the lesser wing of the sphenoid drilled extradurally, depending on the specific approach.[
Extradural anterior clinoidectomy
The originally described extradural Dolenc[
Considerations and complications
Described major complications related to anterior clinoidectomy in modern series include postoperative cerebrospinal fluid (CSF) leak, damage to optic nerve in the form of visual field deficits (either direct neural damage or ischemia due to ophthalmic artery manipulation), oculomotor palsy and intraoperative aneurysm rupture. Each of these will be discussed in the context of the two approaches to clinoidectomy.
CSF rhinorrhea postoperatively occurs when the facial sinuses are, intentionally or inadvertently, made contiguous with the subarachnoid space. In the context of clinoidectomy, this can involve incursion into the frontal, ethmoid or sphenoid sinuses. While ethmoid and frontal sinus involvement can generally be avoided with careful surgical corridor planning, the sphenoid sinus (or, rarely, the ethmoid) can extend into the optic strut and/or the ACP itself (referred to as a pneumatized optic strut or pneumatized clinoid process), necessitating sinus violation for adequate bony removal. Various incidences of this anatomical variant are reported,[
An argument can be made that intradural clinoidectomy may have a lower incidence of CSF rhinorrhea for two reasons. First, through intradural evaluation of the anatomy of the lesion and target corridor, the necessity of clinoidectomy can be further evaluated, and some number of anterior clinoid processes could theoretically be spared. Second, the necessary exposure can be decided intraoperatively and a smaller amount of bony removal may be indicated, possibly avoiding sinus invasion.[
Of the neural structures related to the cavernous sinus and SOF, cranial nerve III is the most commonly affected cranial nerve by clinoidectomy given its size and location directly inferior to the ACP in the first layer of connective tissue overlying the SOF. Depending on the location of the injury, dysfunction frequently may be limited to only the superior branch, producing ptosis and upgaze palsy, or more extensive oculomotor dysfunction.
Intradural series have noted a 10–75% rate of any third nerve dysfunction (transient or permanent) with 4–13% permanent deficit,[
Optic nerve deficit
Cranial nerve II deficits are harder to quantify as a large number of patient series requiring clinoidectomy consist of the patients presenting with preoperative visual field changes harboring craniopharyngiomas, large or giant ICA aneurysms and medial sphenoid wing meningiomas. Modern intradural series describe a small (0–3%) incidence of visual deterioration with either standard or en bloc clinoidectomy,[
Aneurysms of the internal carotid artery around the ACP often necessitate clinoidectomy and are simultaneously at a risk of premature rupture during bone removal. While aneurysm rupture during clinoidectomy is only rarely reported,[
Description of an alternative hybrid technique
We have employed the following hybrid method to potentially engage the advantages of the intradural and extradural techniques. The hybrid method starts with an extradural sphenoid wing osteotomy to the level of the SOF. The dura is then incised parallel to the sphenoid wing lateral to the SOF [
The hybrid method starts with an extradural sphenoid wing osteotomy (sketched for the left-sided approach) to the level of the superior orbital fissure. The dura is then incised parallel to the sphenoid wing lateral to the superior orbital fissure and along the frontal and temporal lobes. The need for further bony removal including clinoidectomy is assessed following gentle elevation of the frontal lobe and release of cerebrospinal fluid through opening the optico-carotid cisterns and inspection of the pathology in relation to the clinoid. Sylvian fissure may be dissected to relieve retraction on the frontal lobe
This exposure allows an early identification of the optic nerve and its protection during clinoidectomy [Figures
The above statements emphasize the advantages and disadvantages of intradural and extradural techniques for clinoidectomy. It is important to note that the surgeon should prefer the method he or she feels most comfortable with. This preference is often affected by the surgeon's training. Extradural clinoidectomy is advantageous during removal of the medial sphenoid wing meningiomas as aggressive bony removal facilitates extradual devascularization of the tumor and may enhance gross tumor removal, especially if the clinoid is infiltrated with tumor. The intradural technique may be preferred for clipping of ophthalmic aneurysms as bony removal can be tailored based on the pathology at hand and clinoidectomy can be done under careful monitoring of the aneurysm to prevent manipulations that would place the aneurysm at risk of intraoperative rupture.
The hybrid method theoretically can be used as a versatile method under both circumstances mentioned above. Cutting the dura along the sphenoid wing will prevent the dural layers from obscuring the clinoid and offers intradural visualization to monitor the lesion and potentially tailor bony removal.
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