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Microsurgical treatment of ophthalmic segment aneurysms
Journal of Clinical Neuroscience 20 (2013) 1145–1148
Contents lists available at SciVerse ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Operative Technique
Microsurgical treatment of ophthalmic segment aneurysms Bradley A. Gross, Rose Du ⇑ Department of Neurological Surgery, Brigham and Women’s Hospital and Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA
a r t i c l e
i n f o
Article history: Received 2 November 2012 Accepted 9 November 2012
Keywords: Aneurysm Clinoidectomy Clipping Dorsal variant Microsurgery Ophthalmic Superior hypophyseal
a b s t r a c t Ophthalmic segment aneurysms refer to superior hypophyseal artery aneurysms, true ophthalmic artery aneurysms, and their dorsal variant. Indications for treatment of these aneurysms include concerning morphological features, large size, visual loss, or rupture. Although narrow-necked aneurysms are ideal endovascular targets, more complex and larger lesions necessitating adjunctive stent or flow-diversion techniques may be suitably treated with long-lasting, effective clip ligation instead. This is particularly relevant in the consideration of ruptured ophthalmic segment aneurysms. This article provides a depiction of microsurgical treatment of ophthalmic segment aneurysms with an accompanying video demonstration. Emphasis is placed on microsurgical anatomy, the intradural anterior clinoidectomy and clipping technique. The intradural anterior clinoidectomy, demonstrated in detail in our Supplementary video, provides significant added exposure of the ophthalmic segment of the internal carotid artery, allowing for improved aneurysm visualization. In the management of superior hypophyseal artery aneurysms, emphasis is placed on identifying and preserving superior hypophyseal artery perforators, using serial fenestrated straight clips rather than a single right-angled fenestrated clip to obliterate the aneurysm. Post-clipping indocyanine green dye angiography is a crucial tool to confirm aneurysm obliteration and the preservation of the parent vasculature and adjacent superior hypophyseal artery perforators. With careful attention to the nuances of microsurgical clipping of ophthalmic segment aneurysms, rewarding results can be obtained. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction Ophthalmic segment aneurysms (Fig. 1) are common and may require treatment due to concerning morphologic features, large size, visual loss, or rupture. Although narrow-necked aneurysms are ideal endovascular targets,1 more complex and larger lesions necessitating adjunctive stent2 or flow-diversion techniques3 may be suitably treated with long-lasting, effective clip ligation instead - a particularly important consideration for ruptured aneurysms.4–6 Their microsurgical management is more nuanced than aneurysms arising more distally along the internal carotid artery (ICA) or at the middle cerebral artery bifurcation; however a mastery of key principles of proximal control, sharp dissection, and intradural anterior clinoidectomy can afford excellent results.4 2. Operative technique 2.1. Perioperative considerations and patient counseling Patients are counseled about the typical risks of cranial surgery (See Supplementary video) including excessive blood loss, ⇑ Corresponding author. Tel.: +1 617 732 5500; fax: +1 617 734 8342. E-mail address: [email protected] (R. Du). 0967-5868/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jocn.2012.11.005
infection and stroke. Germane to ophthalmic segment aneurysms, possible cervical carotid exposure and potential visual loss or cerebrospinal fluid (CSF) leak are also addressed. A preoperative baseline ophthalmic examination should be performed. Cervical carotid anatomy and collateral circulation is evaluated in anticipation of possible temporary cervical carotid occlusion. Patients are kept normotensive and those with ruptured aneurysms undergo ventriculostomy placement prior to treatment as indicated. 2.2. Setup and positioning The patient is placed in a supine position. The head is turned by 30 degrees and extended slightly at the neck. The vertex is lowered making the maxilla the highest point in view. The head is secured in a radiolucent head holder. After induction of anesthesia, somatosensory evoked potentials and electroencephalogram monitoring leads are placed. The neck is prepared for potential exposure of the cervical carotid artery for proximal control. 2.3. Initial opening and craniotomy A gently curved incision is made from the midline down to the zygoma, just posterior to the hairline and no more than 1 cm
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B.A. Gross, R. Du / Journal of Clinical Neuroscience 20 (2013) 1145–1148
Fig. 1. Digital subtraction angiography demonstrating (a) a superior hypophyseal artery aneurysm (arrow, anteroposterior view), (b) ophthalmic artery aneurysm (arrow, anteroposterior view), and (c) dorsal variant ophthalmic artery aneurysm (arrow, lateral view).
anterior to the tragus to avoid injury to the frontalis branch of the facial nerve. After elevating the scalp flap, the temporalis fascia is incised superior to the fat pad. The temporalis muscle is then freed from the fascia and retracted posteroinferiorly, leaving a muscle cuff anteriorly for closure. A pterional craniotomy is performed. The sphenoid ridge is taken down to the base of the anterior clinoid process (ACP). The dura is opened based on the sphenoid ridge and reflected anteriorly. The sylvian fissure is split. 2.4. Anterior clinoidectomy After exposure of the optico-carotid cistern, the falciform ligament is sectioned. A dural incision is then made from the tip of the anterior clinoid process extending along the sphenoid ridge. A second dural incision is made perpendicular to the first and extends medially over the optic canal to the medial falciform ligament. The optic canal is unroofed with a diamond burr to minimize injury to the optic nerve during manipulation of the ACP. It is then removed with a combination of rongeur and highspeed diamond burr, detaching it inferiorly from the optic strut. Copious irrigation is crucial to control heat in close proximity to the optic nerve. After ACP removal, the optic strut may be drilled down further (Fig. 2a, b). The lateral optic nerve sheath is then opened and retracted (Fig. 2c). 2.5. Aneurysm dissection and clipping Sharp dissection about the neck and dome of the aneurysm follows. When treating superior hypophyseal artery (SHA)
aneurysms, attention needs to be paid to the identification and preservation of perforators supplying the pituitary gland and optic chiasm (Fig. 3a). If the aneurysm is ruptured and/or complex, the neck is opened and a clip is placed on the cervical carotid artery for proximal control prior to clipping. SHA aneurysms are treated with serial fenestrated straight clips to preserve vessels supplying the pituitary and optic chiasm (Fig. 3b, c). Ophthalmic and dorsal variant aneurysms are typically managed with a straight or gently curved clip (Fig. 4). Indocyanine green (ICG) angiography is performed to verify aneurysm occlusion and flow preservation in the surrounding vasculature including the ICA, ophthalmic artery, and SHA perforators. If pneumatization of the optic strut is seen, the communication with the sphenoid sinus is sealed with muscle and/or bonewax. The dura is then closed, the bone flap replaced, and the temporalis fascia is sutured followed by the galea and then the skin. 3. Discussion Recent natural history studies have generally suggested a relatively lower risk of rupture for aneurysms of the ophthalmic segment as compared to most other intradural aneurysms.7,8 Grouped along with anterior choroidal artery and ICA bifurcation aneurysms in the recent Japanese Unruptured Cerebral Aneurysm Study, their annual rupture rates were 0.14%, 0%, 1.19%, 1.07%, and 10.61% for 3-4 mm, 5-6 mm, 7-9 mm, 10-24 mm, and giant lesions, respectively.8 Despite these low rupture rates, indications for treatment of ophthalmic segment aneurysms include aneurysm rupture, visual loss, or concerning morphologic features such as
Fig. 2. Intraoperative photographs showing (a) drilling of the optic strut, (b) exposure after anterior clinoidectomy and (c) exposure after opening the lateral optic nerve sheath (arrow).
B.A. Gross, R. Du / Journal of Clinical Neuroscience 20 (2013) 1145–1148
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Fig. 3. Intraoperative photographs showing (a) dissection of superior hypophyseal artery (SHA) aneurysm (note the perforators), (b) serial straight fenestrated clips being employed to occlude the aneurysm, and (c) preservation of SHA perforators, confirmed on indocyanine green angiography.
3.1. Relevant surgical anatomy
Fig. 4. Intraoperative photograph showing the small straight clip used to occlude an ophthalmic artery aneurysm.
large size, irregularity, or aneurysm growth. Recent microsurgical studies have continued to reinforce the efficacy and safety of this treatment modality for the vast majority of ophthalmic segment aneurysms.5,6 Relative contraindications to surgery include significant medical comorbidities and calcification at the aneurysm neck.
The ACP has three connection points - the lesser sphenoid wing laterally, the optic roof superomedially, and the optic strut inferomedially. The roof of the optic canal connects the ACP to the planum sphenoidale, while the optic strut connects the ACP to the body of the sphenoid, separating the optic canal medially from the superior orbital fissure laterally. The ACP has three dural reflections - the falciform ligament, the complete (distal) dural ring, and the incomplete (proximal) dural ring or carotid-oculomotor membrane (COM). The falciform ligament is a dural fold lying posterior to the roof of the optic canal, serving as a potential site of optic nerve compression if the nerve is placed under traction. The COM emanates from the inferior surface of the ACP. It extends from the oculomotor nerve laterally to the ICA medially, marking its transition from cavernous to clinoidal segments. The distal dural ring emanates from the superomedial aspect of the ACP and encircles the ICA, marking the transition from the extradural clinoidal segment to the intradural ophthalmic segment. A resultant dural diverticulum lying medial to the ICA is the carotid cave. Clinoidal aneurysms are often incorrectly dubbed ‘‘carotid cave’’ aneurysms; however they are extradural, lying between the dural rings, not in the carotid cave. Two variants exist - a medial clinoidal and an anterolateral variant (Fig. 5). The ophthalmic segment of the ICA originates at the distal dural ring and terminates at the takeoff of the posterior communicating artery. Typical hemodynamic aneurysms arising from this segment include superior hypophyseal artery (SHA) aneurysms, ophthalmic artery aneurysms and their dorsal variant (Fig. 1). SHA aneurysms
Fig. 5. Three dimensional rotational angiography demonstrating (a) a medial clinoidal aneurysm (arrow) and (b) lateral clinoidal variant aneurysm (arrow).
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B.A. Gross, R. Du / Journal of Clinical Neuroscience 20 (2013) 1145–1148
can be stratified into two variants - a parasellar variant projecting inferiorly toward the sella and a suprasellar variant projecting superiorly. The former is relatively reinforced by the dura of the sella or cavernous sinus and has a low risk of rupture. At times, parasellar SHA aneurysms may extend proximally and inferiorly with further reinforcement by the dura of the carotid cave, serving as a true ‘‘carotid cave’’ aneurysm.
patency of adjacent vessels, including the SHA perforators. Thereafter, meticulous watertight dural closure over the removed ACP is crucial to prevent postoperative CSF leak. Conflicts of interest/disclosures The authors declare that they have no financial or other conflicts of interest in relation to this research and its publication.
3.2. Key principles of surgical management A precise understanding of the distinction of the clinoidal and ophthalmic segments of the ICA is crucial prior to the treatment of ophthalmic segment aneurysms, as clinoidal aneurysms do not possess a risk of subarachnoid hemorrhage unless they extend intradurally. Careful attention to aneurysm calcification on preoperative CT scans is important as attempts to treat the lesion via endovascular means should be given greater consideration if calcification is present at the neck. If surgical treatment is still indicated, adjunctive revascularization may be indicated. At our institution, we remain strong proponents of an intradural anterior clinoidectomy for ophthalmic segment aneurysms. It provides improved exposure of ophthalmic segment aneurysms9 and can be performed at low morbidity with special attention paid to ACP microsurgical anatomy, continuous irrigation during drilling, and a meticulous watertight dural closure. Specific attention should be paid to pneumatization and a connection with the sphenoid sinus after drilling the ACP and optic strut. Of little controversy, it is also important to section the falciform ligament and open the optic nerve sheath early in aneurysm dissection to minimize the risk of injury to the optic nerve. At the time of sharp aneurysm dissection, in cases of SHA aneurysms, careful attention must be paid to the preservation of SHA perforator vessels. Serial fenestrated clips over the ICA rather than a right-angled fenestrated clip should be used when securing SHA aneurysms. After clipping, ICG angiography is a crucial tool to verify aneurysm occlusion and
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jocn.2012.11.005. References 1. Park HK, Horowitz M, Jungreis C, et al. Endovascular treatment of paraclinoid aneurysms: experience with 73 patients. Neurosurgery 2003;53:14–23. 2. Ogilvy CS, Natarajan SK, Jahshan S, et al. Stent-assisted coiling of paraclinoid aneurysms: risks and effectiveness. J Neurointerv Surg 2011;3:14–20. 3. Wong GK, Kwan MC, Ng RY, et al. Flow diverters for treatment of intracranial aneurysms: current status and ongoing clinical trials. J Clin Neurosci 2011;18:737–40. 4. Day AL. Aneurysms of the ophthalmic segment. A clinical and anatomical analysis. J Neurosurg 1990;72:677–91. 5. Sharma BS, Kasliwal MK, Suri A, et al. Outcome following surgery for ophthalmic segment aneurysms. J Clin Neurosci 2010;17:38–42. 6. Zhao J, Wang S, Zhao 3rd Y, et al. Microneurosurgical management of carotidophthalmic aneurysms. J Clin Neurosci 2006;13:330–3. 7. Wiebers DO, Whisnant JP, Huston J, et al. Unruptured intracranial aneurysms: a natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet 2003;362:103–10. 8. UCAS Japan Investigators, Morita A, Kirino T, et al. The natural course of unruptured cerebral aneurysms in a Japanese cohort. N Engl J Med 2012;366:2474–82. 9. Andaluz N, Beretta F, Bernucci C, et al. Evidence for the improved exposure of ophthalmic segment of the internal carotid artery after anterior clinoidectomy: morphometric analysis. Acta Neurochir (Wien) 2006;148:971–5.
Contents lists available at SciVerse ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Operative Technique
Microsurgical treatment of ophthalmic segment aneurysms Bradley A. Gross, Rose Du ⇑ Department of Neurological Surgery, Brigham and Women’s Hospital and Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA
a r t i c l e
i n f o
Article history: Received 2 November 2012 Accepted 9 November 2012
Keywords: Aneurysm Clinoidectomy Clipping Dorsal variant Microsurgery Ophthalmic Superior hypophyseal
a b s t r a c t Ophthalmic segment aneurysms refer to superior hypophyseal artery aneurysms, true ophthalmic artery aneurysms, and their dorsal variant. Indications for treatment of these aneurysms include concerning morphological features, large size, visual loss, or rupture. Although narrow-necked aneurysms are ideal endovascular targets, more complex and larger lesions necessitating adjunctive stent or flow-diversion techniques may be suitably treated with long-lasting, effective clip ligation instead. This is particularly relevant in the consideration of ruptured ophthalmic segment aneurysms. This article provides a depiction of microsurgical treatment of ophthalmic segment aneurysms with an accompanying video demonstration. Emphasis is placed on microsurgical anatomy, the intradural anterior clinoidectomy and clipping technique. The intradural anterior clinoidectomy, demonstrated in detail in our Supplementary video, provides significant added exposure of the ophthalmic segment of the internal carotid artery, allowing for improved aneurysm visualization. In the management of superior hypophyseal artery aneurysms, emphasis is placed on identifying and preserving superior hypophyseal artery perforators, using serial fenestrated straight clips rather than a single right-angled fenestrated clip to obliterate the aneurysm. Post-clipping indocyanine green dye angiography is a crucial tool to confirm aneurysm obliteration and the preservation of the parent vasculature and adjacent superior hypophyseal artery perforators. With careful attention to the nuances of microsurgical clipping of ophthalmic segment aneurysms, rewarding results can be obtained. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction Ophthalmic segment aneurysms (Fig. 1) are common and may require treatment due to concerning morphologic features, large size, visual loss, or rupture. Although narrow-necked aneurysms are ideal endovascular targets,1 more complex and larger lesions necessitating adjunctive stent2 or flow-diversion techniques3 may be suitably treated with long-lasting, effective clip ligation instead - a particularly important consideration for ruptured aneurysms.4–6 Their microsurgical management is more nuanced than aneurysms arising more distally along the internal carotid artery (ICA) or at the middle cerebral artery bifurcation; however a mastery of key principles of proximal control, sharp dissection, and intradural anterior clinoidectomy can afford excellent results.4 2. Operative technique 2.1. Perioperative considerations and patient counseling Patients are counseled about the typical risks of cranial surgery (See Supplementary video) including excessive blood loss, ⇑ Corresponding author. Tel.: +1 617 732 5500; fax: +1 617 734 8342. E-mail address: [email protected] (R. Du). 0967-5868/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jocn.2012.11.005
infection and stroke. Germane to ophthalmic segment aneurysms, possible cervical carotid exposure and potential visual loss or cerebrospinal fluid (CSF) leak are also addressed. A preoperative baseline ophthalmic examination should be performed. Cervical carotid anatomy and collateral circulation is evaluated in anticipation of possible temporary cervical carotid occlusion. Patients are kept normotensive and those with ruptured aneurysms undergo ventriculostomy placement prior to treatment as indicated. 2.2. Setup and positioning The patient is placed in a supine position. The head is turned by 30 degrees and extended slightly at the neck. The vertex is lowered making the maxilla the highest point in view. The head is secured in a radiolucent head holder. After induction of anesthesia, somatosensory evoked potentials and electroencephalogram monitoring leads are placed. The neck is prepared for potential exposure of the cervical carotid artery for proximal control. 2.3. Initial opening and craniotomy A gently curved incision is made from the midline down to the zygoma, just posterior to the hairline and no more than 1 cm
1146
B.A. Gross, R. Du / Journal of Clinical Neuroscience 20 (2013) 1145–1148
Fig. 1. Digital subtraction angiography demonstrating (a) a superior hypophyseal artery aneurysm (arrow, anteroposterior view), (b) ophthalmic artery aneurysm (arrow, anteroposterior view), and (c) dorsal variant ophthalmic artery aneurysm (arrow, lateral view).
anterior to the tragus to avoid injury to the frontalis branch of the facial nerve. After elevating the scalp flap, the temporalis fascia is incised superior to the fat pad. The temporalis muscle is then freed from the fascia and retracted posteroinferiorly, leaving a muscle cuff anteriorly for closure. A pterional craniotomy is performed. The sphenoid ridge is taken down to the base of the anterior clinoid process (ACP). The dura is opened based on the sphenoid ridge and reflected anteriorly. The sylvian fissure is split. 2.4. Anterior clinoidectomy After exposure of the optico-carotid cistern, the falciform ligament is sectioned. A dural incision is then made from the tip of the anterior clinoid process extending along the sphenoid ridge. A second dural incision is made perpendicular to the first and extends medially over the optic canal to the medial falciform ligament. The optic canal is unroofed with a diamond burr to minimize injury to the optic nerve during manipulation of the ACP. It is then removed with a combination of rongeur and highspeed diamond burr, detaching it inferiorly from the optic strut. Copious irrigation is crucial to control heat in close proximity to the optic nerve. After ACP removal, the optic strut may be drilled down further (Fig. 2a, b). The lateral optic nerve sheath is then opened and retracted (Fig. 2c). 2.5. Aneurysm dissection and clipping Sharp dissection about the neck and dome of the aneurysm follows. When treating superior hypophyseal artery (SHA)
aneurysms, attention needs to be paid to the identification and preservation of perforators supplying the pituitary gland and optic chiasm (Fig. 3a). If the aneurysm is ruptured and/or complex, the neck is opened and a clip is placed on the cervical carotid artery for proximal control prior to clipping. SHA aneurysms are treated with serial fenestrated straight clips to preserve vessels supplying the pituitary and optic chiasm (Fig. 3b, c). Ophthalmic and dorsal variant aneurysms are typically managed with a straight or gently curved clip (Fig. 4). Indocyanine green (ICG) angiography is performed to verify aneurysm occlusion and flow preservation in the surrounding vasculature including the ICA, ophthalmic artery, and SHA perforators. If pneumatization of the optic strut is seen, the communication with the sphenoid sinus is sealed with muscle and/or bonewax. The dura is then closed, the bone flap replaced, and the temporalis fascia is sutured followed by the galea and then the skin. 3. Discussion Recent natural history studies have generally suggested a relatively lower risk of rupture for aneurysms of the ophthalmic segment as compared to most other intradural aneurysms.7,8 Grouped along with anterior choroidal artery and ICA bifurcation aneurysms in the recent Japanese Unruptured Cerebral Aneurysm Study, their annual rupture rates were 0.14%, 0%, 1.19%, 1.07%, and 10.61% for 3-4 mm, 5-6 mm, 7-9 mm, 10-24 mm, and giant lesions, respectively.8 Despite these low rupture rates, indications for treatment of ophthalmic segment aneurysms include aneurysm rupture, visual loss, or concerning morphologic features such as
Fig. 2. Intraoperative photographs showing (a) drilling of the optic strut, (b) exposure after anterior clinoidectomy and (c) exposure after opening the lateral optic nerve sheath (arrow).
B.A. Gross, R. Du / Journal of Clinical Neuroscience 20 (2013) 1145–1148
1147
Fig. 3. Intraoperative photographs showing (a) dissection of superior hypophyseal artery (SHA) aneurysm (note the perforators), (b) serial straight fenestrated clips being employed to occlude the aneurysm, and (c) preservation of SHA perforators, confirmed on indocyanine green angiography.
3.1. Relevant surgical anatomy
Fig. 4. Intraoperative photograph showing the small straight clip used to occlude an ophthalmic artery aneurysm.
large size, irregularity, or aneurysm growth. Recent microsurgical studies have continued to reinforce the efficacy and safety of this treatment modality for the vast majority of ophthalmic segment aneurysms.5,6 Relative contraindications to surgery include significant medical comorbidities and calcification at the aneurysm neck.
The ACP has three connection points - the lesser sphenoid wing laterally, the optic roof superomedially, and the optic strut inferomedially. The roof of the optic canal connects the ACP to the planum sphenoidale, while the optic strut connects the ACP to the body of the sphenoid, separating the optic canal medially from the superior orbital fissure laterally. The ACP has three dural reflections - the falciform ligament, the complete (distal) dural ring, and the incomplete (proximal) dural ring or carotid-oculomotor membrane (COM). The falciform ligament is a dural fold lying posterior to the roof of the optic canal, serving as a potential site of optic nerve compression if the nerve is placed under traction. The COM emanates from the inferior surface of the ACP. It extends from the oculomotor nerve laterally to the ICA medially, marking its transition from cavernous to clinoidal segments. The distal dural ring emanates from the superomedial aspect of the ACP and encircles the ICA, marking the transition from the extradural clinoidal segment to the intradural ophthalmic segment. A resultant dural diverticulum lying medial to the ICA is the carotid cave. Clinoidal aneurysms are often incorrectly dubbed ‘‘carotid cave’’ aneurysms; however they are extradural, lying between the dural rings, not in the carotid cave. Two variants exist - a medial clinoidal and an anterolateral variant (Fig. 5). The ophthalmic segment of the ICA originates at the distal dural ring and terminates at the takeoff of the posterior communicating artery. Typical hemodynamic aneurysms arising from this segment include superior hypophyseal artery (SHA) aneurysms, ophthalmic artery aneurysms and their dorsal variant (Fig. 1). SHA aneurysms
Fig. 5. Three dimensional rotational angiography demonstrating (a) a medial clinoidal aneurysm (arrow) and (b) lateral clinoidal variant aneurysm (arrow).
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B.A. Gross, R. Du / Journal of Clinical Neuroscience 20 (2013) 1145–1148
can be stratified into two variants - a parasellar variant projecting inferiorly toward the sella and a suprasellar variant projecting superiorly. The former is relatively reinforced by the dura of the sella or cavernous sinus and has a low risk of rupture. At times, parasellar SHA aneurysms may extend proximally and inferiorly with further reinforcement by the dura of the carotid cave, serving as a true ‘‘carotid cave’’ aneurysm.
patency of adjacent vessels, including the SHA perforators. Thereafter, meticulous watertight dural closure over the removed ACP is crucial to prevent postoperative CSF leak. Conflicts of interest/disclosures The authors declare that they have no financial or other conflicts of interest in relation to this research and its publication.
3.2. Key principles of surgical management A precise understanding of the distinction of the clinoidal and ophthalmic segments of the ICA is crucial prior to the treatment of ophthalmic segment aneurysms, as clinoidal aneurysms do not possess a risk of subarachnoid hemorrhage unless they extend intradurally. Careful attention to aneurysm calcification on preoperative CT scans is important as attempts to treat the lesion via endovascular means should be given greater consideration if calcification is present at the neck. If surgical treatment is still indicated, adjunctive revascularization may be indicated. At our institution, we remain strong proponents of an intradural anterior clinoidectomy for ophthalmic segment aneurysms. It provides improved exposure of ophthalmic segment aneurysms9 and can be performed at low morbidity with special attention paid to ACP microsurgical anatomy, continuous irrigation during drilling, and a meticulous watertight dural closure. Specific attention should be paid to pneumatization and a connection with the sphenoid sinus after drilling the ACP and optic strut. Of little controversy, it is also important to section the falciform ligament and open the optic nerve sheath early in aneurysm dissection to minimize the risk of injury to the optic nerve. At the time of sharp aneurysm dissection, in cases of SHA aneurysms, careful attention must be paid to the preservation of SHA perforator vessels. Serial fenestrated clips over the ICA rather than a right-angled fenestrated clip should be used when securing SHA aneurysms. After clipping, ICG angiography is a crucial tool to verify aneurysm occlusion and
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jocn.2012.11.005. References 1. Park HK, Horowitz M, Jungreis C, et al. Endovascular treatment of paraclinoid aneurysms: experience with 73 patients. Neurosurgery 2003;53:14–23. 2. Ogilvy CS, Natarajan SK, Jahshan S, et al. Stent-assisted coiling of paraclinoid aneurysms: risks and effectiveness. J Neurointerv Surg 2011;3:14–20. 3. Wong GK, Kwan MC, Ng RY, et al. Flow diverters for treatment of intracranial aneurysms: current status and ongoing clinical trials. J Clin Neurosci 2011;18:737–40. 4. Day AL. Aneurysms of the ophthalmic segment. A clinical and anatomical analysis. J Neurosurg 1990;72:677–91. 5. Sharma BS, Kasliwal MK, Suri A, et al. Outcome following surgery for ophthalmic segment aneurysms. J Clin Neurosci 2010;17:38–42. 6. Zhao J, Wang S, Zhao 3rd Y, et al. Microneurosurgical management of carotidophthalmic aneurysms. J Clin Neurosci 2006;13:330–3. 7. Wiebers DO, Whisnant JP, Huston J, et al. Unruptured intracranial aneurysms: a natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet 2003;362:103–10. 8. UCAS Japan Investigators, Morita A, Kirino T, et al. The natural course of unruptured cerebral aneurysms in a Japanese cohort. N Engl J Med 2012;366:2474–82. 9. Andaluz N, Beretta F, Bernucci C, et al. Evidence for the improved exposure of ophthalmic segment of the internal carotid artery after anterior clinoidectomy: morphometric analysis. Acta Neurochir (Wien) 2006;148:971–5.