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Surgery for very large and giant intracranial aneurysms: Results and complications
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.246291
Keywords: Aneurysm clipping, bypass surgery, complication, internal carotid artery, large and giant intracranial aneurysms, outcome, revascularization, ruptured aneurysm, subarachnoid hemorrhage, unruptured aneurysm, vertebral artery
Aneurysms can be classified as very small (≤5 mm), small (5–9 mm), large (10–17 mm), very large (18–24 mm) or giant (defined as those ≥25 mm).[1],[2] Very large (VL) and giant aneurysms are associated with a high risk of subarachnoid hemorrhage (SAH) and cerebral compression with mass effect. They are considered as one of the most challenging lesions to manage and have a poor outcome and prognosis. The outcome in the management of giant aneurysms are very poor because of the higher risk of rupture and mass effect, leading to a high morbidity and mortality.[1],[2],[3] Untreated giant aneurysms have a mortality rate of 68% and 85% at 2 and 5 years after diagnosis, respectively.[4] According to the International Study of Unruptured Intracranial Aneurysms, the chances for rupture are significantly higher in giant aneurysms. In anterior circulation, the annual rate of bleeding for aneurysms sized 7-12 mm and 13-24 mm is 0.5% and 2.9%, respectively, which increases significantly to 8% for the aneurysms greater than 25 mm. In posterior circulation including the internal carotid artery-posterior communicating artery (ICA-PCOM), the annual rate of bleeding for aneurysms sized 7-12 mm and 13-24 mm is 2.9% and 3.7%, respectively, which increases significantly to 10% for the aneurysms greater than 25 mm. Location also plays a crucial role in dictating morbidity and mortality with posterior circulation aneurysms having a higher mortality rate than those found in the anterior circulation.[3] An advanced age and associated comorbidities also play a pivotal role in the prognosis of these patients. According to the Japanese unruptured aneurysm study, the overall rate of rupture of cerebral aneurysms is 0.95% annually. The risk of rupture increases with the increasing size of the aneurysm. The hazard ratios for size categories for aneurysms in the size range of 5 to 6 mm was 1.13; for the size range of 10 to 24 mm was 9.09; and, for aneurysms sized 25 mm or larger, it was 76.26. Regarding the independent risk factors for rupture, aneurysms of 7 mm size or larger were associated with a significantly increased risk of rupture according to the multivariate analysis; and large and giant aneurysms were associated with a very high risk of rupture.[5] These aneurysms can be treated by the endovascular methods (coiling, stent assisted coiling, stent and balloon assisted coiling and flow diversion stents). Microsurgical treatment consists of clip reconstruction, bypass with clipping and trapping or proximal occlusion. In this publication, we have reviewed the outcome and complications of surgical treatment by a single surgeon over a 13-year period.
All patients were operated on by LNS with assistance in some patients by LJK or BVJ. The record review was performed by ZQ following approval from the institutional review board, University of Washington. Pathological examination of the removed aneurysmal wall was done by GJS, a neuropathologist. Record review included evaluation of the patients’ charts, radiographic studies, and follow up. The patient demographics, clinical presentation, preoperative imaging (computed tomographic angiography [CTA], magnetic resonance imaging [MRI], digital subtraction angiography [DSA]), the decision making process (based on clinical history, location/size/morphology of the aneurysm and peri-aneurysmal vessels; availability of donor or conduit vessels), intra- and post-operative imaging (indocyanine green [ICG], DSA, MRI, computed tomography [CT]), hospital course, clinic and outpatient follow up (complications and outcomes assessed by mRs) and delayed imaging (CTA, MRA, DSA looking for occlusion of the aneurysm, bypass and recipient vessel patency, and final stroke territories if any) were reviewed retrospectively. In all cases, an operative drawing by the senior author (LNS) was converted into a drawing by a medical illustrator. Statistical analysis was done using the Statistical Package for the Social Sciences (SPSS) software. In many cases, an experienced neuro-interventionist was involved in the decision making strategy as well as patient counseling when required. If there was a strong likelihood of a bypass during the operation, the patients were given 325 mg of aspirin orally, or 150 mg of clopidogrel, if an allergy to aspirin was present. During surgery, the patient was placed in burst suppression by the anesthesiologist to protect the brain; and, the blood pressure was kept normal (in the case of ruptured aneurysms), or elevated 20% (in the case of unruptured aneurysms). The patient was given 2,500 to 3,000 units of intravenous heparin during the bypass. Neurophysiological monitoring of somatosensory evoked potentials (SSEPs), and motor evoked potentials (MEPs) was used in all but a few emergent cases (in the latter cases, it was not available). The decision to proceed with the cerebral revascularization was done on the basis of the preoperative aneurysm characteristics. The choice of the grafting procedure and bypass conduit was based on the flow required, the complexity of surgery, and the artery being replaced. The techniques used for the bypasses by the senior author have been presented in other papers.[6],[7],[8],[9],[10],[11] The patients operated recently underwent an indocyanine green angiogram, and micro Doppler studies intraoperatively, and in all patients, a postoperative intra-arterial digital subtraction angiogram (IADSA) was performed as well as the duplex ultrasonographic imaging of the graft. Modified Rankin score scale (mRs) was used to measure the preoperative and postoperative functional status of patients, in those patients with an unruptured aneurysm. In the cases with an ruptured aneurysm, the preoperative Hunt and Hess grade and the mRs scores were measured. The patients were followed up with regular clinic visits at eight weekly intervals for 6 months, and then at six months interval thereafter.
A total of 703 aneurysms were operated upon between 2005 to 2018 by the senior author with VL or giant aneurysms being present in 76 cases. VL and giant aneurysms made up 11% of the total aneurysms operated during this time span. Overall, there were 44 VL and 32 giant aneurysms – 62 were in the anterior circulation (35 in the internal carotid artery, 17 in the middle cerebral artery, 8 in the anterior communicating artery, and 2 in the anterior cerebral artery), while 14 were found in the posterior circulation (3 in the vertebral artery, 8 in the basilar artery and 3 in the posterior cerebral artery) [Table 1], [Table 2], [Table 3].
Twenty-four patients presented with SAH (32%); while in forty-nine patients, 52 aneurysms (68%) were unruptured. Out of a total of 76 aneurysms, 63 aneurysms were treated with a bypass procedure and aneurysm occlusion, and 13 aneurysms were treated by microsurgical clipping. Out of 62 anterior circulation aneurysms, the bypass surgery was performed in 49 patients and 13 underwent clipping. In the posterior circulation, all aneurysms were treated with the bypass procedure with aneurysm occlusion [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]. Sixty-nine of the aneurysms presented de novo; 3 were recurrent after the patients harboring them had already undergone previous surgery for clipping the aneurysm; and, 4 were recurrent, as the patients harboring them had already undergone prior coiling or flow diversion procedures.
Unruptured aneurysms: There were 31 (60%) patients with the preoperative mRs score from 0-2, and 21 (40%) patients with the mRs score from 3-5. Postoperatively, 45 patients (87%) had an mRs score of 0-2, 3 patients (6%) had an mRs score of 3-5, and four patients (7%) died [Table 5]. Ruptured aneurysms: There were five (21%) patients with the preoperative Hunt and Hess grade being 3-5, and all had a poor outcome, with 3 patients having the postoperative mRs 3-5, while two expired. Of the 19 (79%) patients who had the preoperative Hunt and Hess grade 1-2, sixteen patients had an mRs score of 0 -2 and only three patients had an mRs score of 3-5 at the last follow up [Table 6]. On the long-term follow up visit, 99% of the aneurysms were found to be occluded. The mean clinical follow up duration was 32.3 months (range: 2 -118 months) and the mean radiological follow up was 29 months (range: 2-104 months). Statistical analysis The preoperative and postoperative mRs score for the unruptured cases were compared statistically by dichotomizing mRs scores at 0-2 and 3-6 and using a McNemar two-sided exact test. It concluded from this evaluation that the postoperative mRs was significantly better (P = 0.004) than the preoperative mRs, denoting a good outcome in patients with unruptured aneurysms treated by microsurgery [Table 5]. The relationship between the preoperative Hunt and Hess grade and the postoperative mRs score in the ruptured cases was assessed using a Kruskal-Wallis two-sided exact test. The preoperative Hunt and Hess grade was significantly related to the postoperative mRs score (P < 0.001), as the patients with the preoperative mRs score of 1-2 had a much lower postoperative mRs than the patients who had the preoperative mRs score of between 3-5. This analysis demonstrates that the outcomes after surgery were strongly correlated to the preoperative Hunt and Hess grade for ruptured giant aneurysms [Table 6]. Complications Ruptured aneurysms: Four patients suffered a brain infarction, out of which two made a good recovery and two expired. One patient had an intraoperative rupture of the aneurysm after the induction of anesthesia prior to dural incision. This patient had a postoperative mRs score of 4 at follow up of two years. One patient developed wound infection and bone flap necrosis, which was managed by wound debridement. One patient developed postoperative extradural hematoma, which was managed conservatively. Three patients had graft-related complications. Out of these 3 patients, two patients required revision of the graft; and, one patient required balloon angioplasty of the graft. Unuptured aneurysms: Four patients developed brain infarction. Out of these, two made a good recovery and two expired. Two patients with an unstable aneurysm had an intraoperative rupture of the aneurysms, and both died. Two patients had postoperative wound infection and two patients developed a subdural hematoma. Five patients suffered from graft-related complications; four underwent graft revision, and in one patient, balloon angioplasty of the graft was performed. The outcome and complications seen in the study are summarized in [Table 7] and [Table 8]. The analysis of patients with the postoperative mRs score of 3-5 is summarized in [Table 11], [Table 12], [Table 13]. The analysis of patients with the postoperative mRs 6 is summarized in [Table 14] and [Table 15].
Case 1: Giant anterior communicating artery aneurysm, clipping and A3-A3 side-to-side intracranial bypass This 21-year old woman had a prior history of fibrous dysplasia and had undergone multiple surgeries in other institutions, which were complicated by bilateral blindness and panhypopituitarism. She presented to us with subarachnoid hemorrhage with her Hunt and Hess grade being 4. Neurological examination revealed an absence of light perception in both her eyes and right facial paresis. Cerebral angiography revealed a giant aneurysm arising from the left A2 vessel, projecting into the right frontal lobe with a large hemorrhage around the neck of the aneurysm. Clipping of the aneurysm along with A3-to-A3 bypass was planned. In the meantime, the patient had another rebleed with left frontal and left intraventricular hemorrhage and neurological deterioration. The patient underwent a bifrontal craniotomy, right orbital osteotomy, A3-to-A3, side-to-side anastomosis via an interhemispheric approach and trapping of the aneurysm [Figure 1]. She had a complex postoperative course with persisting vasospasm and the occurrence of cardiomyopathy requiring endovascular angioplasty and an intra-aortic balloon counterpulsion, respectively. She recovered without any additional neurological deficits and was discharged to domiciliary care. At a follow up of 5 years, she was doing well without any recurrence of the aneurysm.
Case 2: Giant anterior communicating artery aneurysm, temporary trapping to remove the clot, and clip reconstruction This 62-year man presented with worsening headache. He had a history of having presented with a large anterior communicating artery aneurysm 3 years ago. Over the last three years, the aneurysm had significantly increased in size. It was bilobed, projecting toward the ventricle on both the sides, the right lobe being larger than the left. The aneurysmal sac was heavily thrombosed. The overall dimension of the aneurysm was 43 mm in the transverse axis, 23 mm in the superior/inferior axis, and 27 mm in the anteroposterior axis. When assessed by the angiographic images, the filling portion of the aneurysm measured 7.8 × 9.7 × 14.2 mm, with a very broad neck that measured 11 mm. The aneurysm was filling predominantly via the large left A1 artery, although there was also a small right A1 vessel. The patient underwent a bifrontal craniotomy, an orbitofrontoethmoidal osteotomy with an interhemispheric and basal frontal approach [Figure 2]. Microsurgical clipping of the aneurysm was done after its temporary trapping and removal of the clot. The patient had a good recovery without any deficit. At a follow up of seven years, he has been asymptomatic without aneurysm recurrence.
Case 3: Double M1-middle cerebral artery aneurysm, resection with interposition graft This 4-year old girl presented with episodes of severe headaches for two months. Cerebral angiogram revealed two fusiform middle cerebral artery (MCA) aneurysms measuring 25 mm and 14 mm and involving the M1 segment, straddling the anterior temporal artery. She underwent a right frontotemporal craniotomy and orbitotomy, and resection of the two aneurysms. A radial artery graft was placed as an interposition graft. The anterior temporal artery was occluded, and no lenticulostriate artery was seen arising from the M1 segment [Figure 3]. Her postoperative mRs score was 0. She recovered completely and remains normal neurologically for 5 years. At a five-year follow up, she is asymptomatic, has not had a recurrence of the aneurysm and also has a patent graft.
Case 4: Superior hypophyseal artery aneurysm, clipping This 61-year-old woman had presented with severe headaches during radiation treatment for adenocarcinoma of the lung and had been discovered to have a unruptured large internal carotid artery-superior hypophyseal artery aneurysm. Cerebral angiogram showed an aneurysm that was pointing medially, 14 × 10 mm in dimension with a neck dimension of 5 mm. The patient underwent a right frontotemporal craniotomy, posterolateral orbitotomy, anterior clinoidectomy and optic nerve decompression. Microsurgical clip reconstruction of the aneurysm was performed, and another small internal carotid artery aneurysm was clipped. Clipopexy was done to relieve kinking of the internal carotid artery caused by the clips [Figure 4]. The patient was relieved of her symptoms and was without any complications postoperatively.
Case 5: Giant internal carotid artery (ICA) aneurysm, radial artery graft bypass, clip reconstruction This 40-year old physician presented with complaints of rapidly progressive visual loss and severe headache. Neurological examination revealed a left homonymous hemianopsia. Cerebral angiography demonstrated a giant ICA aneurysm involving the terminal ICA segment. Collaterals from the contralateral ICA were poor because of a small caliber anterior cerebral artery on the ipsilateral side. The patient underwent a radial artery graft bypass from the external carotid artery to the MCA, and the aneurysm was clipped with preservation of flow to the anterior choroidal artery [Figure 5]. Postoperatively, the patient had a mild hemiparesis, which resolved after 3 days. He has been back to work as a physician and has been without any deficit for 10 years. The follow up CT angiogram demonstrated graft patency without evidence of aneurysmal recurrence.
Case 6: P1/P2 junction aneurysm with brainstem compression, bypass with trapping This 46-year old man presented with several weeks of episodes of headaches, which were progressively worsening. On neurological examination, he was found to have anisocoria along with visual changes in the form of worsening of sight in the near field and hyperopia. Cerebral angiography showed a partially thrombosed fusiform, 14.9 × 15.4 × 6.4 mm aneurysm at the left P1/P2 junction with the aneurysm neck incorporating the native PCA and with severe compression of the brainstem. The patient underwent a left temporal and retrosigmoid craniotomy, posterior transtemporal-transpetrosal approach and partial resection of the inferior temporal gyrus to approach the aneurysm. Proximal occlusion of the aneurysm was done followed by the placement of a radial artery graft from the occipital artery to the P2 segment of the posterior cerebral artery distal to the aneurysm [Figure 6]. The patient had a good postoperative recovery without any deficit, and had no recurrence at a one-year follow-up visit.
Case 7: A giant vertebral artery aneurysm, with posterior inferior cerebellar artery (PICA) not filling from the contralateral vertebral artery (VA), bypass and trapping This 21-year old man, suffering from Marfan's syndrome, had undergone endovascular occlusion of a giant right ICA aneurysm at 9 years of age at another institution. He presented to us with a giant right vertebral artery aneurysm. He also had a small aneurysm of the right posterior communicating (PCOM) artery, which was supplying the entire right middle cerebral artery territory. A balloon test occlusion of the right vertebral artery did not cause clinical deficit, but the right PICA was not filling from the contralateral vertebral artery injection. Due to the concern about a possible PICA infarct after endovascular occlusion of VA, surgery was elected. The patient underwent a suboccipital craniotomy, far lateral approach, and occlusion of the aneurysm with occipital artery to PICA bypass. The patient had already exhibited early aneurysmal changes in the right posterior communicating artery, which was the collateral source to the right middle cerebral artery. In addition, following the last procedure, the patient had developed an asymptomatic watershed infarct in the right parietal area. Both these findings indicated that the patient would benefit from additional revascularization of the right side of the brain in order to reduce the incidence of aneurysm formation as well as to reduce the chances of right brain ischemia [Figure 7]. Due to this fact, a radial artery graft bypass from the external carotid artery to the M2 segment of middle cerebral artery was performed in this patient. He recovered well without any deficit. Thus, this patient was not eligible for an endovascular flow diversion stent due to the unusual location of the PICA (at its origin from the vertebral artery) in close proximity to the giant vertebral artery aneurysm.
Case 8: Lower basilar artery aneurysm; sephanous vein graft to the posterior cerebral artery, proximal clipping and endovascular coiling This 10-year old boy, who underwent multiple coiling procedures for a lower basilar trunk aneurysm, presented with episodic severe headaches and hemiparesis. The preoperative cerebral angiography revealed that the aneurysm had recurred and was filling through both vertebral arteries that had a right-sided dominance. The posterior communicating arteries were not adequate to support the endovascular occlusion of the basilar artery and a flow diversion stent was not available at that time. The patient underwent a right-sided combined far lateral and transpetrosal approach, with a saphenous vein graft from the right V3 segment of the vertebral artery to the P2 segment of the posterior cerebral artery. Both vertebral arteries just proximal to the aneurysm were occluded using a clip. Postoperative angiography demonstrated the persistent filling of the aneurysm through the contralateral vertebral artery, around the clip blades. Six weeks later, the remaining vertebral artery and the base of the aneurysm were obliterated with coils [Figure 8]. The follow-up at 1 year showed no evidence of aneurysm recurrence. The patient has an mRs score of 0 at a 12-year follow up period.
Case 9: Giant basilar tip aneurysm after multiple coilings, sephanous vein graft bypass, and basilar artery occlusion A 62-year old woman had undergone four coiling procedures for an unruptured basilar tip aneurysm. The procedures had started in 2003. She presented with progressive decline in her neurological status. She was restricted to a wheelchair and her neurological examination was positive for global cognitive dysfunction, expressive aphasia, and spastic quadriparesis. She also had difficulty in swallowing for which a gastrostomy was done. Her preoperative mRs was 5. The brain MRI scan demonstrated a large cyst adjacent to the aneurysm, which was extending into the third and lateral ventricles, and a coil mass which was severely compressing the midbrain. The aneurysm was measuring 26 × 26 × 24 mm in size. Cerebral angiography showed the continued filling of the aneurysm from the basilar artery with the maximum dimension (the height of the aneurysm) of the portion that still had a patent circulation being 17 mm. The patient had an absent posterior communicating artery artery on the left side and a moderate-sized posterior communicating artery (of 1 mm diameter) on the right side. She underwent surgery in three stages; in first stage, the cyst was fenestrated endoscopically. In the second stage, exposure of V2 and V3 segments of the vertebral artery and decompression of the sigmoid sinus and facial nerve were performed by the transtemporal and transpetrosal approaches. The third stage consisted of the bypass procedure with placement of the saphenous vein graft from the vertebral artery (V3 segment) to the right PCA (P2 segment), followed by clip occlusion of the upper basilar artery. During this surgery, the aneurysm could not be visualized due to the coil mass. The patient made a good recovery without any postoperative complications. The postoperative angiogram demonstrated the aneurysm neck filling slightly from the right posterior communicating artery, and through the bypass and a patent graft [Figure 9]. At a 3-year follow-up period, the patient had considerably improved. She was able to speak a few words, walk a few steps with assistance, and her swallowing had improved significantly followed by removal of gastrostomy tube. At a 3-year follow-up visit, her angiogram showed a patent graft with good flow in both posterior cerebral arteries, one supported by the sephanous vein graft and other through the posterior communicating artery. A small stable aneurysm neck remnant was also seen. Thus, due to a single, moderate sized, posterior communicating artery, the endovascular occlusion of the basilar artery was not done[12] A sephanous veing graft was placed because the radial arteries could not be used due to their utilization in the prior operations.
Case 10: Vertebrobasilar junction aneurysm, bypass and subsequent endovascular occlusion of aneurysm; patient developed brain stem stroke This 69-year female patient presented with sixth nerve palsy. Cerebral angiogram showed a 20 mm, partially thrombosed, aneurysm just above the vertebrobasilar junction, with both the vertebral arteries joining the proximal aspect of the neck of the aneurysm. The aneurysm was causing significant brain stem compression and could not be treated with simple endovascular coiling because both the vertebral arteries were joining the aneurysm at the inferior aspect of its sac, and the basilar artery had no collaterals from the posterior communicating artery. Due to this, the patient was offered either of the two choices, either an endovascular treatment utilizing a flow diversion device; or, a bypass to the right posterior cerebral artery followed by endovascular occlusion of the aneurysm. The patient chose to have microsurgery. She underwent a right temporal and retrosigmoid craniotomy, mastoidectomy with presigmoid petrosal approach and a radial artery graft was placed from the external carotid artery to the posterior cerebral artery on the right side. She did well initially after the bypass procedure. Coil embolization of the giant mid-basilar artery aneurysm, and both vertebral arteries was performed subsequently. After the coiling, however, her condition deteriorated, most likely due to the occlusion of perforators. The brain MRI demonstrated multiple ventrolateral pons and medullary infarcts [Figure 10]. Eventually, the patient developed respiratory failure and expired due to the development of brain stem infarcts. For such patients, there is no consistently good solution at present. In other patients with similar aneurysms, we have done bypass followed by proximal occlusion of the major inferior artery, or distal occlusion with good results. Flow diversion embolization has also been done but with variable results.[13]
Case 11: Giant internal carotid artery aneurysm; rupture on induction of anesthesia This 39-year old female patient presented with 2 months of blurred vision, worst in the left inferior quadrant of her visual fields. The cerebral angiogram showed a giant supraclinoid internal carotid artery aneurysm measuring 40 mm. The preoperative balloon occlusion test showed a 35% reduction of transcranial Doppler velocity in the middle cerebral artery, so a permanent endovascular occlusion was not done. She underwent a right frontotemporal craniotomy and orbitozygomatic osteotomy. The patient had an intraoperative rupture of the aneurysm spontaneously upon induction of anesthesia. We decided to proceed with treatment despite the absence of evoked potentials because of her young age. A CT scan showed significant intraventricular and subarachnoid hemorrhage, mass effect and cerebral edema in the right hemisphere and signs of central herniation syndrome. Frontal and temporal lobectomies were done and the aneurysm was trapped. An extracranial-to-intracranial bypass was performed using a radial artery graft, from the external carotid artery to the middle cerebral artery. This was followed by a decompressive craniectomy [Figure 11]. Postoperatively, she did not improve and died. This case demonstrates the presence of a very unstable aneurysm. Perhaps rupture could have been prevented by inducing hypotension during the induction of anesthesia until the aneurysm was occluded.
Case 12: Giant internal carotid artery aneurysm with bypass; occlusion of the large posterior communicating artery; the patient developed a stroke This 77-year old male patient presented to us with progressive visual decline in the right eye with complete visual loss. This manifestation was accompanied by headaches for six weeks. An MRI demonstrated a giant, right-sided supraclinoid internal carotid artery aneurysm measuring 26 mm, with compression on the optic nerve apparatus. The angiogram showed that the aneurysm was heavily thrombosed but the basal portion was still filling. The posterior communicating artery was fetal but with some communication through a tiny P1 segment and was arising from the neck of the aneurysm. All endovascular options were considered, which were not applicable due to the nearly fetal posterior communicating artery and a poor collateral circulation. The patient underwent a right frontotemporal craniotomy with orbital osteotomy. A radial artery bypass graft was placed from the common carotid artery to the M2 segment of the middle cerebral artery. The aneurysm was opened, a lot of thrombus and abnormal material was removed. The internal carotid artery was reconstructed with two fenestrated clips, and the posterior communicating artery appeared to be patent on evaluation using the indocyanine green angiogram and micro-Doppler studies. However, around this time, the motor evoked potential from the left arm and leg was suddenly lost and could not be recovered even with clip readjustment. Postoperatively, the patient developed left-sided hemiplegia. His angiogram showed the occlusion of fetal posterior communicating artery from the internal carotid artery but forward filling of the posterior cerebral artery and the posterior communicating artery from the basilar artery. The MRI scan showed hypothalamic, medial temporal and thalamic infarcts [Figure 12]. At a three year follow up visit, his left-sided hemiplegia has improved with a power of 3/5 in both his extremities. His mRs was 3. An option in this patient would have been to perform the bypass followed by proximal occlusion of the aneurysm without trapping or clipping. This case was still difficult for a pipeline embolization device placement due to the presence of a significant thrombus within the aneurysm and the fetal origin of the posterior cerebral artery from the aneurysm.
The histopathologic examination was performed in the resected 10 very large and 11 giant aneurysms. These aneurysms demonstrated various structural abnormalities, including intimal denudation or fibrous hyperplasia, absence or prominent disruption of the internal elastic lamina, loss of smooth muscle cells of the tunica muscularis with associated variable areas of fibrosis, areas of atherosclerotic change, blood breakdown products, variable primarily lymphocytic mural infiltrates and microcalcifications. Five aneurysms demonstrated abundant thrombosis with organization and an occasional recanalization (as was evident in one case in the present study) [Figure 13].
Over the years, there has been a tremendous evolution in microsurgical and endovascular techniques for managing these difficult lesions.[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27],[28],[29] In the case of ruptured aneurysms, the microsurgical techniques are favored. The role of endovascular modalities is limited due to the need for administration of antiplatelet agents, although coiling followed by placement of a stent after 6 weeks is being used in many centers. Moreover, giant aneurysms with a mass effect, ruptured aneurysms, or bifurcation and trifurcation aneurysms cannot be treated with flow diversion embolization devices. Microsurgical techniques include clip reconstruction and bypasses. Calcification within the aneurysmal neck, the presence of severe atherosclerotic changes in the vessel wall, and excessive thrombosis within the aneurysm may preclude a clipping procedure; under these circumstances, the bypass techniques play a crucial role. In unruptured aneurysms, the endovascular options must be considered. The procedure of coiling has a high recurrence rate. The occasional occlusion of perforators and herniation of the coils within the arterial lumen pose a formidable challenge.[30] The placement of flow diverters has emerged as a ground-breaking procedure although their efficacy, long term complications and results still need to be established in the coming years.[31],[32],[33],[34],[35],[36],[37],[38],[39],[40] Some of the unruptured aneurysms treated in this series may be addressed currently by endovascular means using flow diverters. The crucial issues regarding the endovascular management of aneurysms are the long-term outcome, durability and cost of these procedures, particularly in developing countries. Moreover, patients treated by endovacular methods need to be on a constant follow up while microsurgery provides a definitive treatment with a similar risk and outcome. In our series, good results were achieved with microsurgical procedures but these results may be improved further. Majority of the very large and giant aneurysms treated here were with bypass and proximal occlusion/trapping. Poor outcomes correlated with a poor neurological condition after SAH, or even with the presence of unruptured aneurysms. Two aneurysms ruptured while anesthetic induction was being carried out reflecting a very unstable condition of the aneurysmal sac. Many cases were very difficult to manage, with multiple comorbidities, making them high risk candidates for rupture of the aneurysm. Multiple published trials in the literature regarding microsurgical management of giant aneurysms show that an excellent to good outcome (mRs score 0–3) was obtained in 58% to 84% of the patients, and a mortality rate of 14% to 22% was observed.[41],[42],[43],[44],[45],[46] This series has good outcome in 80% of the patients having a very large and giant aneurysm that was treated with microsurgery, with a mortality rate of 8% (6/73) and a morbidity rate of 12% (9/73). However, the overall good results of 80% (mRs 0-2) are excellent, and can be improved upon if one pre-selects patients for surgery and does not treat patients in a poor preoperative condition. Yet, the pre-selection presents an ethical dilemma since some of these patients in poor condition can be improved after surgery, especially in those with unruptured cases. It is difficult to compare the complications encountered within various series published in the literature due to the differences in the morbidities encountered in dealing with anterior and posterior circulation aneurysms, and the variable definition of a good outcome.[47],[48],[49],[50],[51],[52],[53],[54],[55] [Table 16] summarizes the previous reports of very large and giant aneurysms treated by microsurgery and compares the results of those studies to our study.
Due to their poor natural history and associated complexities in management, the treatment of very large and giant aneurysms is associated with a higher morbidity than that seen in small intracranial aneurysms. The retrospective analysis of our cases shows that a good outcome can be achieved with microsurgical techniques. Endovascular flow diversion is preferred for unruptured internal carotid artery-cavernous sinus and many para-ophthalmic intracranial aneurysms. For ruptured giant intracranial aneurysms, both endovascular and microsurgical treatment should be considered. Bypass with aneurysmal occlusion, followed by clip reconstruction are the main microsurgical treatments for these aneurysms. Therefore, continuing to learn and teach bypass techniques to future generations of neurosurgeons should be a mandatory feature of training programs in neurosurgery. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10], [Table 11], [Table 12], [Table 13], [Table 14], [Table 15], [Table 16]
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