Perspectives Commentary on: Microsurgical Clipping of Unruptured Middle Cerebral Artery Bifurcation Aneurysms: Incidence of and Risk Factors for Procedure-Related Complications by Chung et al. World Neurosurg 83:666-672, 2015
Preoperative Angiography of Middle Cerebral Artery Bifurcation Aneurysms Menno R. Germans1 and R. Loch Macdonald2-4
N
eurosurgical clipping of cerebral aneurysms is a less common procedure for neurosurgeons now compared with those who were trained in the previous century. Nowadays, endovascular techniques have arisen for repair of ruptured aneurysms on the basis of randomized trial evidence showing they are associated with better patient outcomes than clipping in selected cases. Endovascular treatments have also become widely used for unruptured aneurysms, even in the absence of randomized trials to show they are equivalent to or better than neurosurgical clipping (2). The noninvasiveness and potentially lower complications of endovascular coiling compared with neurosurgical clipping draw attention to complication rates for these procedures because efficacy at least for unruptured aneurysms requires years of follow-up that is not evident today. Also, the increased knowledge of the natural history of unruptured aneurysms has led to a significant decrease in the number of patients who need aneurysm treatment (1, 3, 4). The article of Chung et al. encompasses an interesting topic on unruptured middle cerebral artery (MCA) aneurysms that is applicable for the neurosurgeon who is preoperatively assessing a patient’s status in order to perform safe and efficacious aneurysm surgery. Their study describes specific factors that predict complications in the microsurgical treatment of unruptured MCA aneurysms. These factors are based on the preoperative catheter angiogram and include the length of the M1, defined as the distance between the bifurcation of the internal
Key words Complications - Intracranial aneurysm - Microsurgical clipping - Middle cerebral artery - Predictors - Unruptured aneurysm -
Abbreviations and Acronyms MCA: Middle cerebral artery
carotid artery and the main bifurcation of the MCA, angle of the M1 in comparison with the skull base on the anteroposterior angiogram, and projection of the dome on the lateral angiogram view. In multivariate analysis, a shorter M1 segment, larger M1 angle, and posterior inferior aneurysm projection appear to be independent variables that are related to a higher risk for surgical complications. They discuss that these factors can ameliorate the decision making in whether or not to operate on that specific aneurysm. They mention the probable cause for the higher chance of complications with shorter M1 segments, which is likely that there will be more proximity to perforating lateral lenticulostriate arteries. However, the explanation for the other factors is less obvious. What makes the larger angle of the M1 segment more difficult to operate on the MCA aneurysm? It could be an indication that the M1 is lying deeper into the Sylvian fissure or that the MCA is situated more distant to the skull base. In our experience, this increases the depth of dissection needed to expose the aneurysm in the Sylvian fissure, with more manipulation of the brain, Sylvian veins, and such. The posterior inferior projection of the aneurysm makes the dissection around it more demanding because these are the cases where the overlying M2 branches and neighboring lenticulostriate arteries are plastered onto the aneurysm and must be dissected off or somehow preserved during clipping. In view of this, the authors’ observations are valuable and highlight what we envision when we see the angiogram of a patient with an unruptured MCA aneurysm. The distal, anteriorly projecting superficial one will be
From the 1Department of Neurosurgery, St. Elisabeth Hospital, Tilburg, The Netherlands; 2 Division of Neurosurgery, St. Michael’s Hospital; 3Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Centre of the Li Ka Shing Knowledge Institute of St. Michael’s Hospital; and 4Department of Surgery, University of Toronto, Toronto, Ontario, Canada To whom correspondence should be addressed: R. Loch Macdonald, M.D., Ph.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015) 84, 2:222-223. http://dx.doi.org/10.1016/j.wneu.2015.04.003
222
www.SCIENCEDIRECT.com
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2015.04.003
PERSPECTIVES
easy. The bigger it is, the more proximal and more embedded back in the fissure, the more we have to consider carefully whether to repair the aneurysm surgically or not. Strengths of this study are the large number of patients who were prospectively collected and the fact that all patients were treated by surgeons who were trained at the same institution. First, assuming that the surgical results are comparable among the surgeons, this makes the interpretation of the results quite reliable. Second, the use of a standard preoperative catheter angiography for the risk assessment for surgical complications makes the conclusions of this study easy to implement in daily practice. One point that needs to be commented on is the exact causes of the complications. The majority of complications are frontal hypodensities or intracerebral hemorrhages, which could have been a result of frontal lobe retraction or venous infarctions. Hypodensities could also be a result of lenticulostriate artery occlusion. Understanding the exact mechanism of complication could help to optimize the safety of the surgery. For instance, excessive frontal lobe retraction can be prevented by dynamic retraction and distal-to-proximal opening of the fissure. Venous infarction, on the contrary, could be prevented by sacrifice of as few Sylvian veins as possible and assessment of the venous drainage pattern on the preoperative digital subtraction angiography. Artery occlusion can sometimes be detected by intraoperative indocyanine green or fluorescein video angiography, intraoperative angiography, or electrophysiological monitoring. Another interesting point about the study of Chung et al. is the exceptionally low risk of morbidity (1.2%), which is low in
REFERENCES 1. Bederson JB, Awad IA, Wiebers DO, Piepgras D, Haley EC, Brott T, Hademenos G, Chyatte D, Rosenwasser R, Caroselli C: Recommendations for the management of patients with unruptured intracranial aneurysms: a statement for healthcare professionals from the Stroke Council of the American Heart Association. Stroke 31:2742-2750, 2000. 2. Darsaut TE, Estrade L, Jamali S, Bojanowski MW, Chagnon M, Raymond J: Uncertainty and agreement in the management of unruptured intracranial aneurysms. J Neurosurg 120:618-623, 2014. 3. Etminan N, Beseoglu K, Barrow DL, Bederson J, Brown RD, Connolly ES, Derdeyn CP, Hanggi D, Hasan D, Juvela S, Kasuya H, Kirkpatrick PJ, Knuckey N, Koivisto T, Lanzino G, Lawton MT, LeRoux P, McDougall CG, Mee E, Mocco J, Molyneux A, Morgan MK, Mori K, Morita A,
comparison with previous published results of aneurysm clipping (5, 6). That is despite there being 416 patients operated on over 11 years by 5 surgeons, which is only 7 or 8 cases a year per surgeon. With such a low rate of morbidity, the microsurgical treatment of MCA aneurysms might be an acceptable and durable option for patients. Taking the rupture risk for unruptured MCA aneurysms according to the PHASES score into account (4), all MCA aneurysms that are larger than 7 mm might be good candidates for surgical treatment because the risk for rupture in 5 years will outweigh the risk for surgery. This morbidity rate is also competing with the morbidity after endovascular MCA aneurysm treatment and is reflected in the probable preferred surgical treatment of this type of unruptured aneurysm according to a recent review (7). On the other hand, single-center, retrospective reports by the treating physicians always have optimistically high efficacy rates and low complications. Without any standard postoperative imaging or neurocognitive assessment, it is likely that at least some of the 3.6% of procedure-related complications were important to the patient even if they were not to the surgeon. Cases that are more likely to be associated with complications like M1 segment aneurysms, those with an early frontal branch, and cases when multiple aneurysms were treated were excluded. Those lost to follow-up were excluded. These patients did not come back for follow-up, perhaps because they are dead or disabled. Finally, this assessment is unusual in that it examines a great number of factors associated with potential complications, including aneurysm size, calcifications, and such. Many studies find aneurysm size, calcifications, thrombus, and associated atherosclerosis are risk factors for complications. Chung et al. did not find this, perhaps due to the small number of end point events.
Murayama Y, Nagahiro S, Pasqualin A, Raabe A, Raymond J, Rinkel GJ, Rufenacht D, Seifert V, Spears J, Steiger HJ, Steinmetz H, Torner JC, Vajkoczy P, Wanke I, Wong GK, Wong JH, Macdonald RL: Multidisciplinary consensus on assessment of unruptured intracranial aneurysms: proposal of an international research group. Stroke 45:1523-1530, 2014. 4. Greving JP, Wermer MJ, Brown RD, Morita A, Juvela S, Yonekura M, Ishibashi T, Torner JC, Nakayama T, Rinkel GJ, Algra A: Development of the PHASES score for prediction of risk of rupture of intracranial aneurysms: a pooled analysis of six prospective cohort studies. Lancet Neurol 13:59-66, 2014.
6. Raaymakers TW, Rinkel GJ, Limburg M, Algra A: Mortality and morbidity of surgery for unruptured intracranial aneurysms: a meta-analysis. Stroke 29: 1531-1538, 1998. 7. Zijlstra IA, Verbaan D, Majoie CB, Vandertop P, van den Berg R: Coiling and clipping of middle cerebral artery aneurysms: a systematic review on clinical and imaging outcome. J Neurointerv Surg 2014 [Epub ahead of print].
Citation: World Neurosurg. (2015) 84, 2:222-223. http://dx.doi.org/10.1016/j.wneu.2015.04.003 Journal homepage: www.WORLDNEUROSURGERY.org
5. King JT, Berlin JA, Flamm ES: Morbidity and mortality from elective surgery for asymptomatic, unruptured, intracranial aneurysms: a meta-analysis. J Neurosurg 81:837-842, 1994.
WORLD NEUROSURGERY 84 [2]: 222-223, AUGUST 2015
Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
223
Preoperative Angiography of Middle Cerebral Artery Bifurcation Aneurysms Menno R. Germans1 and R. Loch Macdonald2-4
N
eurosurgical clipping of cerebral aneurysms is a less common procedure for neurosurgeons now compared with those who were trained in the previous century. Nowadays, endovascular techniques have arisen for repair of ruptured aneurysms on the basis of randomized trial evidence showing they are associated with better patient outcomes than clipping in selected cases. Endovascular treatments have also become widely used for unruptured aneurysms, even in the absence of randomized trials to show they are equivalent to or better than neurosurgical clipping (2). The noninvasiveness and potentially lower complications of endovascular coiling compared with neurosurgical clipping draw attention to complication rates for these procedures because efficacy at least for unruptured aneurysms requires years of follow-up that is not evident today. Also, the increased knowledge of the natural history of unruptured aneurysms has led to a significant decrease in the number of patients who need aneurysm treatment (1, 3, 4). The article of Chung et al. encompasses an interesting topic on unruptured middle cerebral artery (MCA) aneurysms that is applicable for the neurosurgeon who is preoperatively assessing a patient’s status in order to perform safe and efficacious aneurysm surgery. Their study describes specific factors that predict complications in the microsurgical treatment of unruptured MCA aneurysms. These factors are based on the preoperative catheter angiogram and include the length of the M1, defined as the distance between the bifurcation of the internal
Key words Complications - Intracranial aneurysm - Microsurgical clipping - Middle cerebral artery - Predictors - Unruptured aneurysm -
Abbreviations and Acronyms MCA: Middle cerebral artery
carotid artery and the main bifurcation of the MCA, angle of the M1 in comparison with the skull base on the anteroposterior angiogram, and projection of the dome on the lateral angiogram view. In multivariate analysis, a shorter M1 segment, larger M1 angle, and posterior inferior aneurysm projection appear to be independent variables that are related to a higher risk for surgical complications. They discuss that these factors can ameliorate the decision making in whether or not to operate on that specific aneurysm. They mention the probable cause for the higher chance of complications with shorter M1 segments, which is likely that there will be more proximity to perforating lateral lenticulostriate arteries. However, the explanation for the other factors is less obvious. What makes the larger angle of the M1 segment more difficult to operate on the MCA aneurysm? It could be an indication that the M1 is lying deeper into the Sylvian fissure or that the MCA is situated more distant to the skull base. In our experience, this increases the depth of dissection needed to expose the aneurysm in the Sylvian fissure, with more manipulation of the brain, Sylvian veins, and such. The posterior inferior projection of the aneurysm makes the dissection around it more demanding because these are the cases where the overlying M2 branches and neighboring lenticulostriate arteries are plastered onto the aneurysm and must be dissected off or somehow preserved during clipping. In view of this, the authors’ observations are valuable and highlight what we envision when we see the angiogram of a patient with an unruptured MCA aneurysm. The distal, anteriorly projecting superficial one will be
From the 1Department of Neurosurgery, St. Elisabeth Hospital, Tilburg, The Netherlands; 2 Division of Neurosurgery, St. Michael’s Hospital; 3Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Centre of the Li Ka Shing Knowledge Institute of St. Michael’s Hospital; and 4Department of Surgery, University of Toronto, Toronto, Ontario, Canada To whom correspondence should be addressed: R. Loch Macdonald, M.D., Ph.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015) 84, 2:222-223. http://dx.doi.org/10.1016/j.wneu.2015.04.003
222
www.SCIENCEDIRECT.com
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2015.04.003
PERSPECTIVES
easy. The bigger it is, the more proximal and more embedded back in the fissure, the more we have to consider carefully whether to repair the aneurysm surgically or not. Strengths of this study are the large number of patients who were prospectively collected and the fact that all patients were treated by surgeons who were trained at the same institution. First, assuming that the surgical results are comparable among the surgeons, this makes the interpretation of the results quite reliable. Second, the use of a standard preoperative catheter angiography for the risk assessment for surgical complications makes the conclusions of this study easy to implement in daily practice. One point that needs to be commented on is the exact causes of the complications. The majority of complications are frontal hypodensities or intracerebral hemorrhages, which could have been a result of frontal lobe retraction or venous infarctions. Hypodensities could also be a result of lenticulostriate artery occlusion. Understanding the exact mechanism of complication could help to optimize the safety of the surgery. For instance, excessive frontal lobe retraction can be prevented by dynamic retraction and distal-to-proximal opening of the fissure. Venous infarction, on the contrary, could be prevented by sacrifice of as few Sylvian veins as possible and assessment of the venous drainage pattern on the preoperative digital subtraction angiography. Artery occlusion can sometimes be detected by intraoperative indocyanine green or fluorescein video angiography, intraoperative angiography, or electrophysiological monitoring. Another interesting point about the study of Chung et al. is the exceptionally low risk of morbidity (1.2%), which is low in
REFERENCES 1. Bederson JB, Awad IA, Wiebers DO, Piepgras D, Haley EC, Brott T, Hademenos G, Chyatte D, Rosenwasser R, Caroselli C: Recommendations for the management of patients with unruptured intracranial aneurysms: a statement for healthcare professionals from the Stroke Council of the American Heart Association. Stroke 31:2742-2750, 2000. 2. Darsaut TE, Estrade L, Jamali S, Bojanowski MW, Chagnon M, Raymond J: Uncertainty and agreement in the management of unruptured intracranial aneurysms. J Neurosurg 120:618-623, 2014. 3. Etminan N, Beseoglu K, Barrow DL, Bederson J, Brown RD, Connolly ES, Derdeyn CP, Hanggi D, Hasan D, Juvela S, Kasuya H, Kirkpatrick PJ, Knuckey N, Koivisto T, Lanzino G, Lawton MT, LeRoux P, McDougall CG, Mee E, Mocco J, Molyneux A, Morgan MK, Mori K, Morita A,
comparison with previous published results of aneurysm clipping (5, 6). That is despite there being 416 patients operated on over 11 years by 5 surgeons, which is only 7 or 8 cases a year per surgeon. With such a low rate of morbidity, the microsurgical treatment of MCA aneurysms might be an acceptable and durable option for patients. Taking the rupture risk for unruptured MCA aneurysms according to the PHASES score into account (4), all MCA aneurysms that are larger than 7 mm might be good candidates for surgical treatment because the risk for rupture in 5 years will outweigh the risk for surgery. This morbidity rate is also competing with the morbidity after endovascular MCA aneurysm treatment and is reflected in the probable preferred surgical treatment of this type of unruptured aneurysm according to a recent review (7). On the other hand, single-center, retrospective reports by the treating physicians always have optimistically high efficacy rates and low complications. Without any standard postoperative imaging or neurocognitive assessment, it is likely that at least some of the 3.6% of procedure-related complications were important to the patient even if they were not to the surgeon. Cases that are more likely to be associated with complications like M1 segment aneurysms, those with an early frontal branch, and cases when multiple aneurysms were treated were excluded. Those lost to follow-up were excluded. These patients did not come back for follow-up, perhaps because they are dead or disabled. Finally, this assessment is unusual in that it examines a great number of factors associated with potential complications, including aneurysm size, calcifications, and such. Many studies find aneurysm size, calcifications, thrombus, and associated atherosclerosis are risk factors for complications. Chung et al. did not find this, perhaps due to the small number of end point events.
Murayama Y, Nagahiro S, Pasqualin A, Raabe A, Raymond J, Rinkel GJ, Rufenacht D, Seifert V, Spears J, Steiger HJ, Steinmetz H, Torner JC, Vajkoczy P, Wanke I, Wong GK, Wong JH, Macdonald RL: Multidisciplinary consensus on assessment of unruptured intracranial aneurysms: proposal of an international research group. Stroke 45:1523-1530, 2014. 4. Greving JP, Wermer MJ, Brown RD, Morita A, Juvela S, Yonekura M, Ishibashi T, Torner JC, Nakayama T, Rinkel GJ, Algra A: Development of the PHASES score for prediction of risk of rupture of intracranial aneurysms: a pooled analysis of six prospective cohort studies. Lancet Neurol 13:59-66, 2014.
6. Raaymakers TW, Rinkel GJ, Limburg M, Algra A: Mortality and morbidity of surgery for unruptured intracranial aneurysms: a meta-analysis. Stroke 29: 1531-1538, 1998. 7. Zijlstra IA, Verbaan D, Majoie CB, Vandertop P, van den Berg R: Coiling and clipping of middle cerebral artery aneurysms: a systematic review on clinical and imaging outcome. J Neurointerv Surg 2014 [Epub ahead of print].
Citation: World Neurosurg. (2015) 84, 2:222-223. http://dx.doi.org/10.1016/j.wneu.2015.04.003 Journal homepage: www.WORLDNEUROSURGERY.org
5. King JT, Berlin JA, Flamm ES: Morbidity and mortality from elective surgery for asymptomatic, unruptured, intracranial aneurysms: a meta-analysis. J Neurosurg 81:837-842, 1994.
WORLD NEUROSURGERY 84 [2]: 222-223, AUGUST 2015
Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
223
