They are characterized clinically by their tendency to occur at a younger age
They frequently rupture at a younger age compared to other intracranial aneurysms 5).
Treatment is recommended since they tend to bleed at a lower age than other aneurysms 8).
The presence of multiple perforators in this area along with the angle of origin often skewed toward the MCA or the anterior cerebral artery primarily can make treatment challenging 9).
They are surgically characterized by the technical difficulties posed by their domes being adherent to the frontal lobe, their location at the apex of the sylvian fissure, and their relation to myriad perforator complexes 10).
The surgical treatment of ICA bifurcation aneurysms is particularly challenging, due to their location at the highest point of the ICA and the presence of multiple perforators at this level that may be adherent to the back side of the aneurysm 11)
Endovascular treatment of ICA bifurcation aneurysms is feasible and effective and is associated with high immediate angiographic occlusion rates. However, retreatment rates and procedure-related morbidity and mortality are non-negligible 12).
Periprocedural complications following endovascular treatment of ICA terminus aneurysms are not negligible. Aneurysms at this location are at a high risk of ischemic stroke in the territory of the ipsilateral MCA (either from distal emboli during the procedure or clot formation at the level of the neck with impairment of distal MCA flow), a potential source of serious morbidity and mortality 13) 14) 15).
In the meta-analysis of Morales-Valero et al., perioperative morbidity rates were approximately 4% and mortality rates were 3%. Perioperative stroke was a major contributor to morbidity and mortality, occurring in approximately 3% of patients. Although good long-term neurologic outcome was achieved in 90% of patients regardless of aneurysm rupture status, the periprocedural complication rate reported is not trivial. Particularly worrisome is the procedure-related mortality of 4% for unruptured and 6% for ruptured ICA bifurcation aneurysms. These findings stress the importance of proper patient selection because these aneurysms are often adequately and effectively treatable with surgical clip ligation. The high retreatment rate observed in the meta-analysis and in the own series is similar to that reported for aneurysms located in other bifurcation points 16).
Fifty-one patients with ICAbifAs were treated in the study period out of which 40 patients underwent microsurgical clipping. The median age was 48 yr (range 14-68 yr). Nearly 95% of the patients presented in a good clinical grade (World Federation of Neurological Surgeons grade 1 and 2). At 6-mo follow-up, 36 patients (90%) had good clinical outcome (Glasgow Outcome Scale 4 and 5). According to their direction, ICAbifAs were grouped as anteriorly directed (10 cases), superiorly directed (23 cases), and posteriorly directed (7 cases). Operative techniques and nuances utilized depend on aneurysmal direction and are presented here.
An appropriate surgical strategy based on the direction of ICAbifAs as per the preoperative radiology, meticulous dissection of aneurysmal wall from adjacent perforators, and clip application with the aim of remodeling the ICA bifurcation are integral to achieving a good outcome 17).
Fifty-nine patients with 61 unruptured ICAbifAs were included. Seven aneurysms were treated surgically (11.5 %), 22 underwent endovascular treatment (36 %), and 32 were managed conservatively (52.5 %). In the surgical group, short- and long-term complete aneurysm occlusion rates were 100 % with no cases of perioperative or long-term permanent morbidity or treatment-related mortality. In the endovascular group, two patients (11.7 %) with giant aneurysms had perioperative thromboembolic events with transient morbidity. There was one case of aneurysm rupture at follow-up in a giant aneurysm treated with partial coil embolization. Complete/near-complete occlusion rates were 63 %. There was one case of aneurysm rupture after 114 aneurysm-years of follow-up in the conservative management group (0.89 %/year), but no ruptures were observed in small aneurysms selected for conservative management.
Unruptured small ICAbifAs have a benign natural history. In patients selected for treatment, excellent results can be achieved in the vast majority of patients with judicious use of endovascular and surgical therapy 18).
A total of 58 patients with ICA bifurcation aneurysms were treated. By interdisciplinary consensus, 30 aneurysms were assigned for coiling and 28 for clipping. Patients who underwent surgical clipping were younger and had larger aneurysms. More patients were assigned to coiling if their aneurysms originated only from the ICA bifurcation or projected superiorly. For the combined angiographic endpoint, complete and nearly complete occlusion (Raymond-Roy I + II), similar rates of 96% (coiling) or 100% (clipping) could be achieved. Raymond-Roy I occlusion occurred more often after clipping (79% vs 41% coiling). Follow-up of the endovascular group showed minor recanalization of the aneurysm neck (Raymond-Roy II) in 42%. One patient (4%) showed a major recanalization (Raymond-Roy III) and needed re-treatment. For incidental findings, no bleeding complications or new persistent neurological deficits occurred during follow-up.
Treatment of ICA bifurcation aneurysms after interdisciplinary assignment to clipping or coiling is effective and safe. Despite significantly more minor recanalizations after coiling, the re-treatment rate was very low, and no bleeding was observed during follow-up. Multivariate analysis revealed that origin only from the ICA bifurcation was an independent predictor of aneurysm recanalization after endovascular treatment 19).
The records of 65 patients with 66 ICA BA were retrieved from data prospectively accrued between September 1999 and July 2013. Clinical and morphological outcomes of the aneurysms were assessed, including technical aspects of treatment.
The aneurysms under study were directed either superiorly (41/66, 62.1%), anteriorly (24/66, 36.4%), or posteriorly (1/66, 1.5%), and all were devoid of perforators. Aneurysmal necks were situated symmetrically at the terminal ICA (37/66, 56.1%) or slightly deviated to the proximal A1 segment (29/66, 43.9%). The steam-shaped S microcatheter (73.8%) was most commonly used to select the aneurysms, and the single microcatheter technique was most commonly applied (56.1%) to perform coil embolization, followed by balloon remodelling (21.2%), multiple microcatheter (15.1%), and stent-protection (7.6%). Successful aneurysmal occlusion was achieved in 100% of cases, with no procedure-related morbidity or mortality. Imaging performed in the course of follow-up (mean duration 27.3 months) confirmed stable occlusion of most lesions (47/53, 88.7%).
Through tailored technical strategies, ICA BA are amenable to safe and effective endovascular coil embolization, with a tendency for stable occlusion long-term 20).
Morales-Valero et al. performed a comprehensive literature search for reports on contemporary endovascular treatment of ICA bifurcation aneurysms from 2000 to 2013, and we reviewed our experience. We extracted information regarding periprocedural complications, procedure-related morbidity and mortality, immediate angiographic outcome, long-term clinical and angiographic outcome, and retreatment rate. Event rates were pooled across studies by using random-effects meta-analysis.
Including our series of 37 patients, 6 studies with 158 patients were analyzed. Approximately 60% of the aneurysms presented as unruptured; 88.0% (95% CI, 68.0%-96.0%) of aneurysms showed complete or near-complete occlusion at immediate postoperative angiography compared with 82.0% (95% CI, 73.0%-88.0%) at last follow-up. The procedure-related morbidity and mortality were 3.0% (95% CI, 1.0%-7.0%) and 3.0% (95% CI, 1.0%-8.0%), respectively. The retreatment rate was 14.0% (95% CI, 8.0%-25.0%). Good neurologic outcome was achieved in 93.0% (95% CI, 86.0%-97.0%) of patients.
Endovascular treatment of ICA bifurcation aneurysms is feasible and effective and is associated with high immediate angiographic occlusion rates. However, retreatment rates and procedure-related morbidity and mortality are non-negligible 21).
Internal carotid artery (ICA) bifurcation aneurysms are relatively uncommon and frequently rupture at a younger age compared to other intracranial aneurysms.
Gupta et al treated a total of 999 patients for intracranial aneurysms, of whom 89 (8.9%) had ICA bifurcation aneurysms, and 42 of the 89 patients were 30 years of age or younger. The study analyzed the clinical records of 70 patients with ICA bifurcation aneurysms treated from mid 1997 to mid 2003. Multiple aneurysms were present in 15 patients. Digital subtraction angiography films were studied in 55 patients to identify vasospasm and aneurysm projection. The aneurysm projected superiorly in most of these patients (37/55, 67.3%).
They preferred to minimize frontal lobe retraction, so widely opened the sylvian fissure to approach the ICA bifurcation and aneurysm neck. Elective temporary clipping was employed before the final dissection and permanent clip application. Vasospasm was present in 24 (43.6%) of 55 patients. Forty-eight (68.6%) of the 70 patients had good outcome, 14 (20%) had poor outcome, and eight (11.4%) died. Patients with ICA bifurcation aneurysms tend to bleed at a much younger age compared to those with other intracranial aneurysms. Wide opening of the sylvian fissure and elective temporary clipping of the ICA reduces the risk of intraoperative rupture and perforator injury. Mortality was mainly due to poor clinical grade and intraoperative premature aneurysm rupture 22).
A series of 25 patients treated by clipping under the operating microscope are analyzed and compared with previous cases. Twenty-five patients, 11 men and 14 women (mean age 51 years), were treated by the same neurosurgeon. Seventeen patients presented with subarachnoid hemorrhage (Hunt & Kosnik Grade I in three, II in five, III in two, IV in seven), five with unruptured ICA bifurcation aneurysms, and three with unruptured ICA bifurcation aneurysms but another ruptured aneurysm. There were 23 small, one large, and one giant ICA bifurcation aneurysms. The projection was superior in 12, anterior in seven, and posterior in six cases. Pterional approach was employed for all cases. Outcomes were evaluated at discharge with the Glasgow Outcome Scale. Favorable outcomes (good recovery (GR) and moderate disability (MD)) were obtained in ten of 17 patients with ruptured ICA bifurcation aneurysm. Favorable outcomes were significantly greater in Grades I and II (three in I, four in II) than in Grades III and IV (one in III, two in IV; P=0.0498). Seven of eight patients with unruptured ICA bifurcation aneurysm had favorable outcomes. Temporary clipping and projection of the aneurysm did not affect the outcome. Causative factors of unfavorable outcomes were primary brain damage in cases of small and large aneurysms and perforator damage in the case of giant aneurysm. Poor clinical grade and vasospasm are the causative factors of poor outcome in patients with ruptured ICA bifurcation aneurysm. Preservation of perforators is crucial in cases of giant aneurysm. Clipping of unruptured ICA bifurcation aneurysms is recommended since they tend to bleed at a lower age than other aneurysms 23).
A 70-year-old man with progressive visual disturbances, left superior quadrantanopsia, and right-sided papilledema underwent imaging that demonstrated a right internal carotid artery (ICA) terminus aneurysm with third-ventricle mass effect and ipsilateral optic nerve and chiasm compression. We performed a right modified orbitozygomatic craniotomy, with proximal control and dissection of the aneurysm and small perforator arteries. Temporary ICA and anterior cerebral artery (ACA) clips allowed placement of a large curved permanent clip, reconstructing the ICA bifurcation and maintaining adequate patency of the ACA and middle cerebral artery. Complete aneurysm obliteration was confirmed by intraoperative indocyanine green angiography and postoperative CT angiography. The video can be found here: http://youtu.be/5WEEgmA-g2A 24).
A 64-year-old woman, with visual deficit, harboring a large wide-necked aneurysm located at the junction between left internal carotid artery and left A1 segment of anterior cerebral artery, was submitted to endovascular treatment. As she had pre-existing occlusion of left internal carotid, approach from the contralateral internal carotid was used to advance the pipeline embolization device through the anterior communicating artery and place the flow diverter horizontally across the neck (from M1 to A1). Coil embolization was also performed through a microcatheter navigated via posterior communicating artery. The intervention was uneventful, with total aneurysm occlusion. Patient presented with visual improvement on follow-up.
Horizontal deployment of pipeline embolization device appears to be an acceptable and feasible alternative to treat internal carotid bifurcation aneurysms. Long-term follow-up and a greater number of cases are mandatory to establish the safety of this strategy 25).
A surgical case of an eleven year old boy with excellent outcome is reported, with a subsequent review on the subject. Patients may present with classical subarachnoidal hemorrhage, but also with compressive signs with bigger and unruptured lesions. Initial management of these cases is basically the same of older patients, considering their age, weight and special intensive care for infants 26).
A 58-year-old hypertensive woman presenting with mild headaches underwent computed tomography, which showed a nonruptured aneurysm of the left internal carotid artery. She subsequently underwent cerebral angiography, confirming that the aneurysm was located at the left terminal carotid segment with a wide neck. INTERVENTION: Using a cross-over approach from the contralateral internal carotid artery, a new self-expandable stent was advanced through the anterior communicating artery and placed horizontally across the aneurysm neck. Aneurysm occlusion was performed by subsequent trans-stent catheterization of the aneurysm and coil packing.
Successful stent placement allowed subtotal coil occlusion of the aneurysm with a good anatomic and clinical result. No complications were encountered. The new self-expandable stent is a highly flexible, low-profile device that can be safely navigated through tortuous intracranial vessels even in a crossover technique. Its radial force and closed cell design is suitable for stent-assisted coiling and may be superior to stents with an open cell design 27).