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Intradural versus Extradural Removal of the Anterior Clinoid Process
Perspectives Commentary on: Complications of Anterior Clinoidectomy Through Lateral Supraorbital Approach by Romani et al. pp. 698-703.
Peter Vajkoczy, M.D. Professor, Department of Neurosurgery Charite Universitätsmedizin Berlin
Intradural versus Extradural Removal of the Anterior Clinoid Process Peter Vajkoczy
T
he treatment of complex lesions located at or close to the anterior skull base may necessitate the removal of the anterior clinoid process to achieve adequate neurovascular control during surgical manipulation. The most frequent situation in which an anterior clinoidectomy is indicated is microsurgical treatment of paraophthalmic aneurysms. Anterior clinoidectomy primarily aims at visualizing the segment of the internal carotid artery proximal to the aneurysm (i.e., the clinoidal segment) to provide enough room for temporary control of the vessel. Additional unroofing of the optic canal allows the surgeon to free the optic nerve and provides additional room for manipulating the aneurysm sac safely. The second frequent indication for anterior clinoidectomy when dealing with vascular lesions is microsurgical treatment of complex aneurysms located at the basilar tip. Especially when choosing a pterional-transcavernous approach, anterior clinoidectomy represents an early key step for providing room and, more important, adequate orientation for attacking the cavernous sinus and optimal visualization of the distal basilar artery (2).
Anterior clinoidectomy plays a central role in removal of parasellar tumors, including meningiomas originating at the medial sphenoid wing, the anterior clinoid process, or the optic canal. In addition, surgery of large tuberculum sellae meningiomas extending into the optic canal may benefit from anterior clinoidectomy to optimize decompression of the optic nerve. Generally, it is our policy to remove the anterior clinoid in the context of skull base tumor surgery when (a) the tumor is extending into the optic canal, (b) a hyperostotic anterior clinoid is narrowing the optic canal, or (c) the optic nerve is stretched over the tumor surface and anterior clinoidectomy and unroofing of the optic canal would release the nerve and provide space for manipulation. However, surgery should be kept safe and simple. The potential complications, such as direct or thermal optic nerve injury, vascular
Key words 䡲 Complications 䡲 Intradural 䡲 Lateral supraorbital approach 䡲 Tailored anterior clinoidectomy 䡲 Tumors 䡲 Vascular 䡲 Visual outcome
WORLD NEUROSURGERY 77 [5/6]: 615-616, MAY/JUNE 2012
injuries, and cerebrospinal fluid leak, and the additional operating room time should not be underestimated when deciding to perform anterior clinoidectomy. It is recommended to tailor the indication and extent of anterior clinoidectomy to the need of the individual surgical situation. Although the necessity of anterior clinoidectomy is undisputed, the optimal surgical strategy has been controversial for many years. Both the extradural and the intradural approaches have their proponents and have been discussed extensively in the literature. In the literature, the stated advantages of extradural clinoidectomy are an improved control over the anterior clinoid, early devascularization of the tumor, avoidance of intradural drilling, limited need for intradural dissection, and a straightforward approach to the internal carotid artery after the dura has been opened (3). The stated advantages of intradural clinoidectomy are better visualization of the paraophthalmic artery and the aneurysm, easier identification of the optic canal, better control over the optic nerve, and the ability to tailor the extent of clinoidectomy better to the need of the individual situation (4). In our eyes, these arguments all are more or less valid. It is advisable not to be too dogmatic, and surgeons dealing with the anterior clinoid process should be familiar with both techniques of its removal and should know how and when best to take advantage of them. Another issue frequently discussed is the technique of clinoidectomy after the anterior clinoid process has been exposed. Traditionally, the anterior clinoid process is drilled down with a diamond bit using the eggshell technique, and the remaining base is broken when it has been liberated from the surrounding dural attachments. Cautious irrigation during this maneuver is mandatory to prevent heat injury to the optic nerve. Nevertheless, using the standard drill down in the basal cistern,
Department of Neurosurgery, Charite Universitätsmedizin Berlin, Berlin, Germany To whom correspondence should be addressed: Peter Vajkoczy, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2012) 77, 5/6:615-616. DOI: 10.1016/j.wneu.2011.10.026
www.WORLDNEUROSURGERY.org
615
PERSPECTIVES
especially when approaching the clinoid via the intradural route, carries a significant risk for major neurovascular complications. As an alternative, the use of an ultrasonic bone aspirator has been proposed more recently to remove the anterior clinoid process more safely (1). This technical detail seems to be attractive at first glance. However, in our experience, the use of the bone Cavitron ultrasonic aspirator has so far proven to be a slow technique lacking the adequately sized aspirator tips. The traditional craniotomy approach to the anterior clinoid process, whether intradural or extradural, is via a pterional craniotomy. Proponents of the extradural clinoidectomy especially prefer the pterional approach because it allows for a pretemporal extension, facilitating transection of the meningo-orbital ligament and mobilization of the dura propria off the anterior clinoid. Romani et al. have adjusted the microsurgical technique of anterior clinoidectomy to an approach via a mini-lateral supraorbital craniotomy. Intuitively, we would assume that a purely lateral subfrontal approach through a keyhole craniotomy to the anterior clinoid process should restrict the maneuverability, at least when coming from extradurally. Nevertheless, the authors have reported a successful clinoidectomy in their initial technical report.
REFERENCES 1. Hadeishi H, Suzuki A, Yasui N, Satou Y: Anterior clinoidectomy and opening of the internal auditory canal using an ultrasonic bone curette. Neurosurgery 52:867-870, 2003.
2. Krisht AF, Krayenbühl N, Sercl D, Bikmaz K, Kadri PA: Results of microsurgical clipping of 50 high com-
616
www.SCIENCEDIRECT.com
Romani et al. now report their clinical data with respect to surgical complications and outcome. In 82 patients with neoplastic and vascular lesions, anterior clinoidectomy was performed through the lateral supraorbital approach. The fact that ⬎80% of the clinoids were removed through an intradural approach confirms the potential limitation of this restricted approach. Nevertheless, the excellent results of this series are in accordance with other contemporary series approaching the anterior clinoid process via a pterional approach and confirm the feasibility of the authors’ concept. I will try this technique. The ultrasonic bone dissector was used in 40% of the cases, whereas the remaining clinoid processes were removed using a conventional drill. The ultrasonic bone dissector was used in five of the seven patients who experienced postoperative visual complications suggesting that this device carries an increased risk of damaging the optic nerve. In summary, anterior clinoidectomy is a central step in successful management of tumors and vascular lesions within the parasellar region. Romani et al. show that an anterior clinoidectomy can be performed successfully and safely via a supraorbital keyhole approach. The only limitation seems to be the restriction to an intradural approach to the anterior clinoid process.
plexity basilar apex aneurysms. Neurosurgery 60: 242-250, 2007. 3. Otani N, Muroi C, Yano H, Khan N, Pangalu A, Yonekawa Y: Surgical management of tuberculum sellae meningioma: role of selective extradural anterior clinoidectomy. Br J Neurosurg 20:129-138, 2006. 4. Seifert V, Güresir E, Vatter H: Exclusively intradural exposure and clip reconstruction in complex paracli-
noid aneurysms. Acta Neurochir (Wien) 5153:21032109, 2011. Citation: World Neurosurg. (2012) 77, 5/6:615-616. DOI: 10.1016/j.wneu.2011.10.026 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2012 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, DOI:10.1016/j.wneu.2011.10.026
Peter Vajkoczy, M.D. Professor, Department of Neurosurgery Charite Universitätsmedizin Berlin
Intradural versus Extradural Removal of the Anterior Clinoid Process Peter Vajkoczy
T
he treatment of complex lesions located at or close to the anterior skull base may necessitate the removal of the anterior clinoid process to achieve adequate neurovascular control during surgical manipulation. The most frequent situation in which an anterior clinoidectomy is indicated is microsurgical treatment of paraophthalmic aneurysms. Anterior clinoidectomy primarily aims at visualizing the segment of the internal carotid artery proximal to the aneurysm (i.e., the clinoidal segment) to provide enough room for temporary control of the vessel. Additional unroofing of the optic canal allows the surgeon to free the optic nerve and provides additional room for manipulating the aneurysm sac safely. The second frequent indication for anterior clinoidectomy when dealing with vascular lesions is microsurgical treatment of complex aneurysms located at the basilar tip. Especially when choosing a pterional-transcavernous approach, anterior clinoidectomy represents an early key step for providing room and, more important, adequate orientation for attacking the cavernous sinus and optimal visualization of the distal basilar artery (2).
Anterior clinoidectomy plays a central role in removal of parasellar tumors, including meningiomas originating at the medial sphenoid wing, the anterior clinoid process, or the optic canal. In addition, surgery of large tuberculum sellae meningiomas extending into the optic canal may benefit from anterior clinoidectomy to optimize decompression of the optic nerve. Generally, it is our policy to remove the anterior clinoid in the context of skull base tumor surgery when (a) the tumor is extending into the optic canal, (b) a hyperostotic anterior clinoid is narrowing the optic canal, or (c) the optic nerve is stretched over the tumor surface and anterior clinoidectomy and unroofing of the optic canal would release the nerve and provide space for manipulation. However, surgery should be kept safe and simple. The potential complications, such as direct or thermal optic nerve injury, vascular
Key words 䡲 Complications 䡲 Intradural 䡲 Lateral supraorbital approach 䡲 Tailored anterior clinoidectomy 䡲 Tumors 䡲 Vascular 䡲 Visual outcome
WORLD NEUROSURGERY 77 [5/6]: 615-616, MAY/JUNE 2012
injuries, and cerebrospinal fluid leak, and the additional operating room time should not be underestimated when deciding to perform anterior clinoidectomy. It is recommended to tailor the indication and extent of anterior clinoidectomy to the need of the individual surgical situation. Although the necessity of anterior clinoidectomy is undisputed, the optimal surgical strategy has been controversial for many years. Both the extradural and the intradural approaches have their proponents and have been discussed extensively in the literature. In the literature, the stated advantages of extradural clinoidectomy are an improved control over the anterior clinoid, early devascularization of the tumor, avoidance of intradural drilling, limited need for intradural dissection, and a straightforward approach to the internal carotid artery after the dura has been opened (3). The stated advantages of intradural clinoidectomy are better visualization of the paraophthalmic artery and the aneurysm, easier identification of the optic canal, better control over the optic nerve, and the ability to tailor the extent of clinoidectomy better to the need of the individual situation (4). In our eyes, these arguments all are more or less valid. It is advisable not to be too dogmatic, and surgeons dealing with the anterior clinoid process should be familiar with both techniques of its removal and should know how and when best to take advantage of them. Another issue frequently discussed is the technique of clinoidectomy after the anterior clinoid process has been exposed. Traditionally, the anterior clinoid process is drilled down with a diamond bit using the eggshell technique, and the remaining base is broken when it has been liberated from the surrounding dural attachments. Cautious irrigation during this maneuver is mandatory to prevent heat injury to the optic nerve. Nevertheless, using the standard drill down in the basal cistern,
Department of Neurosurgery, Charite Universitätsmedizin Berlin, Berlin, Germany To whom correspondence should be addressed: Peter Vajkoczy, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2012) 77, 5/6:615-616. DOI: 10.1016/j.wneu.2011.10.026
www.WORLDNEUROSURGERY.org
615
PERSPECTIVES
especially when approaching the clinoid via the intradural route, carries a significant risk for major neurovascular complications. As an alternative, the use of an ultrasonic bone aspirator has been proposed more recently to remove the anterior clinoid process more safely (1). This technical detail seems to be attractive at first glance. However, in our experience, the use of the bone Cavitron ultrasonic aspirator has so far proven to be a slow technique lacking the adequately sized aspirator tips. The traditional craniotomy approach to the anterior clinoid process, whether intradural or extradural, is via a pterional craniotomy. Proponents of the extradural clinoidectomy especially prefer the pterional approach because it allows for a pretemporal extension, facilitating transection of the meningo-orbital ligament and mobilization of the dura propria off the anterior clinoid. Romani et al. have adjusted the microsurgical technique of anterior clinoidectomy to an approach via a mini-lateral supraorbital craniotomy. Intuitively, we would assume that a purely lateral subfrontal approach through a keyhole craniotomy to the anterior clinoid process should restrict the maneuverability, at least when coming from extradurally. Nevertheless, the authors have reported a successful clinoidectomy in their initial technical report.
REFERENCES 1. Hadeishi H, Suzuki A, Yasui N, Satou Y: Anterior clinoidectomy and opening of the internal auditory canal using an ultrasonic bone curette. Neurosurgery 52:867-870, 2003.
2. Krisht AF, Krayenbühl N, Sercl D, Bikmaz K, Kadri PA: Results of microsurgical clipping of 50 high com-
616
www.SCIENCEDIRECT.com
Romani et al. now report their clinical data with respect to surgical complications and outcome. In 82 patients with neoplastic and vascular lesions, anterior clinoidectomy was performed through the lateral supraorbital approach. The fact that ⬎80% of the clinoids were removed through an intradural approach confirms the potential limitation of this restricted approach. Nevertheless, the excellent results of this series are in accordance with other contemporary series approaching the anterior clinoid process via a pterional approach and confirm the feasibility of the authors’ concept. I will try this technique. The ultrasonic bone dissector was used in 40% of the cases, whereas the remaining clinoid processes were removed using a conventional drill. The ultrasonic bone dissector was used in five of the seven patients who experienced postoperative visual complications suggesting that this device carries an increased risk of damaging the optic nerve. In summary, anterior clinoidectomy is a central step in successful management of tumors and vascular lesions within the parasellar region. Romani et al. show that an anterior clinoidectomy can be performed successfully and safely via a supraorbital keyhole approach. The only limitation seems to be the restriction to an intradural approach to the anterior clinoid process.
plexity basilar apex aneurysms. Neurosurgery 60: 242-250, 2007. 3. Otani N, Muroi C, Yano H, Khan N, Pangalu A, Yonekawa Y: Surgical management of tuberculum sellae meningioma: role of selective extradural anterior clinoidectomy. Br J Neurosurg 20:129-138, 2006. 4. Seifert V, Güresir E, Vatter H: Exclusively intradural exposure and clip reconstruction in complex paracli-
noid aneurysms. Acta Neurochir (Wien) 5153:21032109, 2011. Citation: World Neurosurg. (2012) 77, 5/6:615-616. DOI: 10.1016/j.wneu.2011.10.026 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter © 2012 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, DOI:10.1016/j.wneu.2011.10.026