Abstract
Cerebrovascular surgery is associated with relatively higher mortality and morbidity in comparison to other subspecialties of neurosurgery. Advancements in surgical technology, anesthesia, and intensive care have improved the overall outcome in recent years. Understanding the common complications will guide neurosurgeons to more appropriately prognosticate and formulate treatment protocols. In this chapter, we briefly discuss the common complications encountered in the practice of cerebrovascular surgery.
Keywords
aneurysm, arteriovenous malformation, Moyamoya disease, carotid endarterectomy, carotid artery stenting
Highlights
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Cerebrovascular surgery is associated with relatively higher mortality and morbidity in comparison to other sub-specialties of neurosurgery.
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Advances in surgical technology, technical expertise, neuro-anesthesia and neuro-intensive care have improved the overall outcome in recent years for vascular neurosurgery.
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Understanding the common complications and the nuances to avoid them will guide neurosurgeons towards appropriate prognostication and formulation of treatment protocols.
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We present a brief overview of common complications encountered in the practice of vascular neurosurgery.
Introduction
Cerebrovascular surgery is a dual-edged sword. On one hand, this neurosurgical branch is highly rewarding, offering lifesaving treatments for potentially lethal intracranial vascular pathologies; on the other hand, it carries relatively higher rates of morbidity and mortality among neurosurgical specialties. The latter can be very well gauged from the fact that the 30-day postsurgical mortality rates for clipping of unruptured aneurysms (1.0% to 5.5%) and for clipping of ruptured aneurysms (7.4% to 13.4%) are significantly higher than those for brain tumor surgery (2.3%) and epilepsy surgery (0%). Based on various single- and multi-institutional studies, the overall complication rate for cerebrovascular surgery ranges from 2% to 17%. However, a recent study analyzing the complication and mortality in cerebrovascular surgery based on the National Surgical Quality Improvement Program (NSQIP) database has revealed a complication rate of 30.9%, and patients who had at least one complication were found to have significantly increased odds for 30-day postoperative mortality. Thus, complication avoidance in vascular neurosurgery is a vital component of achieving good patient outcomes and preventing postoperative mortality. A significant proportion of complications in cerebrovascular neurosurgery may be avoidable through specific technical practices, teamwork, and specialization. This overview and the ensuing section on complications in cerebrovascular neurosurgery represent a step toward recognizing and addressing these complications.
Neurosurgery for Intracranial Aneurysms
The single most important factor to improve the outcome can be ensured by individualizing the treatment of each patient. Since the publication of the International Subarachnoid Aneurysm Trial (ISAT) in 2002, there has been plenty of comparison between outcomes of endovascular coiling versus surgical clipping. A total of 2143 (endovascular = 1073 and surgical clipping = 1070) patients were randomized. About 23.7% of patients who underwent endovascular coiling were dependent or dead at 1 year compared with 30.6% of patients who had their aneurysm surgically clipped ( P <0.002). This led to a relative/absolute risk reduction of dependency or death at 1 year of 22.6% versus 6.9%. Rebleeding risk at 1 year was 2 per 1276 patient-years in the endovascular group versus 0 per 1081 patient-years in the surgical group.
At 10 years, rebleeding was more likely after endovascular coiling than after neurosurgical clipping; however, the risk was small, and the probability of disability-free survival was significantly greater in the endovascular group than in the neurosurgical group. Other large trials show higher recanalization rate after coiling (20% according to Ferns et al., 2009). Metaanalysis by Li et al. in 2013 suggested that endovascular treatment is associated with higher rates of rebleeding. The six-year result of the Barrow ruptured aneurysm trial (BRAT trial 2015) suggested that complete aneurysm obliteration at 6 years was achieved in 96% (111/116) of the clipping group and in 48% (23/48) of the coiling group ( P < 0.0001). Overall retreatment rates were 4.6% (13/280) for clipping and 16.4% (21/128) for coiling ( P < 0.0001). The outcomes for posterior circulation aneurysms continued to favor coiling. Subgroup analysis for saccular aneurysms shows there was no difference in outcome of intent-to-treat analysis. However, of the 178 clip-assigned patients with saccular aneurysms, 1 patient (<1%) was crossed over to coiling, and 64 (36%) of the 178 coil-assigned patients were crossed over to clipping. The Cerebral Aneurysm Rerupture after Treatment (CARAT) Study suggested that the degree of aneurysm occlusion after treatment was strongly associated with risk of rerupture (overall risk: 1.1% for complete occlusion, 2.9% for 91% to 99% occlusion, 5.9% for 70% to 90%, 17.6% for <70%; P <0.0001 in univariate and multivariable analysis). Overall risk of rerupture tended to be greater after coil embolization compared with surgical clipping (3.4% vs 1.3%; P <0.092).
Overall, patient-related factors (such as age and overall health), aneurysm-related factors (symptoms, size, location, configuration, and presence of an intracerebral hemorrhage), and the experience of the surgeon predict the complications and outcome. A number of aneurysms simply are not ideal for surgical management, including those in elderly patients, in patients with poor neurologic condition, and in patients presenting with cerebral vasospasm; aneurysms that are difficult to surgically access; and multiple aneurysms requiring multiple craniotomies for treatment. Many of these aneurysms are better treated by endovascular therapy because of recent advances in this discipline. Many aneurysms, however, still require surgical treatment. This includes fusiform, blister-like, very small, very large, thrombotic, and wide-necked aneurysms as well as those presenting with a clinically significant intracerebral hemorrhage. However, the endovascular treatment options have expanded in these cases as well.
Complications of Microsurgery
Direct Injury
Avoiding direct injury to the brain involves the use of surgical adjuncts, appropriate exposure, and brain relaxation. Minimizing the use of retractors to preserve veins is essential. Surgeons must be careful about brain protection during temporary occlusion. Judicious use of bypass procedures is an important skill in a surgeon’s armamentarium. Intraoperative imaging with digital subtraction angiography or indocyanine green videoangiography is a proven adjunct to check for adequate occlusion of the aneurysm and distal patency of the vessels.
Incomplete Obliteration
Durability is the major advantage of surgical clip ligation of an aneurysm over current endovascular options. With the use of modern aneurysm clips, the risk of recurrence after appropriate clipping is very low. Indocyanine green videoangiography has provided beautiful fluorescent images of aneurysms before and after clipping.
Compromise of Parent Vessel
Complex clipping strategies can be used to completely obliterate aneurysms and to ensure the patency of perforating vessels and parent arteries. Some aneurysms simply are not suitable for either endovascular treatment or surgical clipping and require sacrifice of the parent artery and a bypass with either the saphenous vein or the radial artery to resupply the circulation eliminated by the sacrifice.
Intraoperative Rupture
Perhaps the most dramatic and potentially devastating complication of aneurysm surgery is intraoperative rupture (IOR). Sluzewski et al. noticed that the clinical outcome of IOR reflects an all-or-none phenomenon: Patients either do very well or die, which is probably related to the rapidity with which hemostasis can be achieved (or not) and intracranial pressure controlled (or not).
As with most surgical complications, this one is better avoided than managed, but the vascular neurosurgeons must prepare for IOR in every surgery. Adequate exposure, sharp dissection, proximal control, and use of temporary clips are the primary means of avoiding IOR. Intraoperative tear of neck is more difficult to manage than rupture of dome. Barrow and Spetzler (2011) described a cotton-clipping technique in which a tear is covered with a piece of cotton and held in place with a suction device. The aneurysm clip can then be applied more distally on the cotton, using it as a bolster, preserving the patency.
Complications of Endovascular Treatment
Intraoperative Rupture
An intraprocedural rupture may not always be evident on the angiographic images. Changes in the patient’s vital signs and neurologic status can be a useful guide. A diminished or stagnant runoff of contrast from the internal carotid artery may reflect the pressure changes during the rupture of the aneurysm. Careful handling of the wire and catheter prevents potential rupture. Rupture of the aneurysm during coil placement can be seen as migration of coils into the subarachnoid space. The formation of a good “cage” early during the embolization procedure, in order to secure the aneurysm, is important. Aneurysms in the anterior communicating artery and those with a small dome size are likely to be risk factors for IOR.
Complications of Coil Embolization/Stent/Flow Diverter
The procedure-related morbidity and mortality are more for unruptured (~15%) aneurysms in comparison to ruptured ones (~10%). The thromboembolic complications related to the introducer catheter, the microcatheter, or the aneurysm itself may often be clinically silent. However, manifestation of stroke is not unlikely.
Compromise of the parent vessel or branch vessel may result from either inadvertent progressive coil packing in an anatomically hazardous pattern or from sudden prolapse of the coils into the parent artery due to coil instability; compromise also may occur during attempts to remove a damaged or ensnared coil. Balloon-assisted aneurysm coiling (using balloon inflation to temporarily remodel the neck of the aneurysm) can be helpful for wide-neck aneurysms; however, it may increase the risk of a thromboembolic phenomenon. The commonly used stents (Neuroform or Enterprise) may be associated with thromboembolic events and institution of anti-platelet therapy should be confirmed before their use. Deploying stents (especially the Pipeline Embolization Device) in patients with tortuous vasculature is technically difficult and tri-axial catheter systems should be duly considered in such cases.
The introduction of flow diverters has revolutionized the field of aneurysm treatment. However, complications are not uncommon.
Zhou et al. published in 2017 a metaanalysis of all papers up to January 2016 discussing complications of flow diverters for treatment of intracranial aneurysms. The complication rate for unruptured intracranial aneurysms was significantly lower than that for ruptured intracranial aneurysms (14.6% vs 30.6%; P <0.05). The incidence of procedural technical complication was 9.4%. Poor stent opening was the major cause, followed by wire perforation. The operative complication rate was nearly double for posterior circulation aneurysms compared with anterior circulation aneurysms. The neurologic morbidity rate was 4.5%. The specific causes were ischemia > intracranial hemorrhages > rebleeding. The permanent morbidity rate and mortality rates were 3.7% (95% confidence interval [CI] 2.5%–4.9%) and 2.8% (95% CI 1.2%–4.4%), respectively. In-stent thrombosis, stent migration, and delayed hemorrhage are other complications. Strict antiplatelet regimen, increasing experience of endovascular surgeons, and advancement of technology have improved the outcome.
Postoperative Complications Common to Either Mode of Treatment
Vasospasm
Cerebral vasospasm remains a significant source of morbidity and mortality in patients with subarachnoid hemorrhage (SAH) after an aneurysmal rupture. It has been discussed in detail elsewhere in the present book. Nimodipine has been proven as a prophylactic agent since 1989. Intraarterial milrinone has recently gained interest as a rescue agent. Endovascular balloon angioplasty is generally used when medication fails. Simvastatin in aneurysmal subarachnoid haemorrhage (STASH, 2014) trial did not detect any benefit in the use of simvastatin for long-term or short-term outcome in patients with aneurysmal SAH.
Hydrocephalus
Hydrocephalus can occur in approximately one-fourth of patients, and its onset can be acute, within 48 hours after SAH or, rarely, chronic.
Electrolyte and Metabolic Imbalance
Hyponatremia is common after aneurysmal SAH. Hypernatremia, hypokalemia, and hypomagnesemia are rare but are associated with poor outcome.
Related posts:
Medical Complications in Neurosurgery
Complications of AVM Microsurgery; Steal Phenomenon and Management of Residual AVM
Complications in Vestibular Schwannoma Patients
Procedure-Related Complications: AVMs
Complications of Surgery for Peripheral Nerve Injuries and Tumors
Complications of Surgery for Intrinsic Spinal Cord Tumors
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