Abstract
Anatomical variations in the middle cerebral artery affect outcomes of mechanical thrombectomy in M1 occlusion cases. However, the relationship between middle cerebral artery branching patterns―specifically trifurcation and bifurcation―and mechanical thrombectomy outcomes remains unclear. This study investigated that relationship and attempted to identify optimal mechanical thrombectomy strategies for trifurcation patterns. We retrospectively analyzed patients treated with mechanical thrombectomy for M1 occlusion at our institution between 2019 and 2024. Patients were categorized into bifurcation and trifurcation groups based on middle cerebral artery branching patterns, and differences in outcomes between the groups were analyzed. In the trifurcation group, further analysis compared characteristics between patients with and without successful recanalization, defined as a modified Thrombolysis in Cerebral Infarction score of 2b-3. Among 98 patients (trifurcation, n = 21; bifurcation, n = 77), the trifurcation group showed lower successful recanalization rates (57% vs. 91%, p = 0.001) and higher procedural complication rates, including distal thrombus migration (62% vs. 36%, p = 0.047) and symptomatic intracerebral hemorrhage (38% vs. 14%, p = 0.027), compared with the bifurcation group. A multivariate modified Poisson regression demonstrated that the trifurcation pattern was independently associated with reduced successful recanalization (relative risk = 0.22; 95% confidence interval, 0.09-0.53; p = 0.001). In trifurcation cases, contact aspiration achieved higher successful recanalization rates than the combined technique (100% vs. 44%, p = 0.009). Moreover, in combined technique cases, direct contact between the aspiration catheter and thrombus significantly improved recanalization rates (77% vs. 0%, p < 0.001) without increasing complications. Trifurcation anatomy hindered effective clot engagement by the aspiration catheter because of narrow M2 diameters and large branching angles, resulting in lower successful recanalization rates compared with bifurcation.
Keywords: bifurcation, mechanical thrombectomy, middle cerebral artery, trifurcation
Introduction
Recent randomized controlled trials demonstrated the efficacy of endovascular mechanical thrombectomy (MT) in patients with acute ischemic stroke (AIS) caused by emergent large vessel occlusion (LVO).1-3) Advances in endovascular devices and procedural strategies have led to higher recanalization rates and improved clinical outcomes. As a result, MT has become the standard treatment for patients with LVO who meet the relevant criteria. Occlusion of the middle cerebral artery (MCA) is the most common type of LVO in patients with AIS. Recent studies have reported that anatomical variations of the MCA―including vessel curvature, diameter, primary occlusion site, and the M1-M2 angulation―are associated with successful recanalization (Thrombolysis in Cerebral Infarction [TICI] ≥2b) and clinical outcomes.4-8)
Branching patterns of the MCA are defined by the division of the main trunk into smaller branches, with bifurcation and trifurcation being the most commonly described types.9-11) A recent systematic review reported bifurcation in 69.9% of cases (range: 58.1%-92.7%) and trifurcation in 27% (range: 7.3%-40.4%).11) Therefore, encountering a trifurcation pattern in MCA occlusion cases is not uncommon. However, the relationship between MCA branching patterns and MT outcomes remains unclear.
In the present study, we focused on MCA branching patterns, specifically bifurcation and trifurcation, and analyzed differences in procedural and clinical outcomes following MT. We also aimed to identify optimal MT strategies for effectively managing M1 occlusions with trifurcation patterns.
Methods
Patient population
The present study was approved by the local Institutional Review Board (OJH-202410) and conducted in accordance with the guidelines of the Strengthening the Reporting of Observational Studies in Epidemiology statement. Patients' informed consent was not required because this study was non-invasive and retrospective. Data were collected from 107 consecutive patients who underwent emergent MT for AIS due to M1 segment occlusion at our institution between April 2019 and June 2024. This study included adult patients (18 years or older) who underwent MT for AIS with occlusion of the M1 segment of the MCA. Exclusion criteria were: (1) AIS caused by intracranial stenosis or dissection, (2) cases in which MCA branching patterns could not be identified during hospitalization, and (3) cases with missing data on the 90-day modified Rankin Scale (mRS) score.
Data variables
Clinical data included demographics (age and sex), medical history (hypertension, diabetes mellitus, atrial fibrillation, and hyperlipidemia), Alberta Stroke Program Early Computed Tomography Score (ASPECTS), premorbid mRS score, use of intravenous thrombolysis, MCA branching patterns (bifurcation or trifurcation) on both the affected and non-affected sides, diameter of the largest M2 branch in the affected MCA, the bending angle between the M1 and M2 segments,5) the last known well-to-recanalization time, puncture-to-recanalization time, number of thrombectomy attempts, modified Thrombolysis in Cerebral Infarction (mTICI) score, and type of MT technique used (contact aspiration, stent retriever, or combined technique).
MT procedure and evaluation
All procedures were performed under local anesthesia. Patients without contraindications received 0.9 mg/kg of intravenous alteplase before endovascular thrombectomy (EVT). All first passes for M1 occlusions were performed at our institution using a combined technique. For the MT procedure, a microcatheter was navigated beyond the occluded artery into the M2 branch (superior, middle, or inferior trunk). Cerebral angiography was then performed through the microcatheter to confirm successful passage beyond the thrombus. A stent retriever was deployed from the M2 to the M1 segment across the thrombus, while an aspiration catheter (AC) was advanced as close as possible to the proximal surface of the thrombus to facilitate clot retrieval. From the second pass onward, the operator selected 1 of the 2 approaches―aspiration or the combined technique―to achieve successful recanalization. For instance, the aspiration technique was often chosen when navigating the microcatheter beyond the occlusion site was difficult. The selection of the AC and stent retriever was left to the discretion of the individual interventionalist. Based on the location of the AC tip within the vessel, cases were divided into 2 groups: the distal AC group (tip positioned adjacent, as close as possible, to the proximal surface of the thrombus in the MCA) and proximal AC group (tip not in contact with the proximal surface of the thrombus).
The primary outcome was successful recanalization, defined as a mTICI score of 2b, 2c, or 3. Secondary outcomes included the 90-day mRS score, dichotomized as good outcome (0-2) or poor outcome (3-6). Intraoperative thrombus migration to distal vessels was defined as the occurrence of emboli beyond the initial occlusion site during EVT, as indicated by the absence of distal arterial branches on final angiography. Symptomatic intracerebral hemorrhage was defined as any intracranial hemorrhage accompanied by a worsening National Institutes of Health Stroke Scale score of ≥4 within 24 hrs.12)
Evaluation of MCA branching patterns
MCA branching patterns were classified based on the division of the main trunk into smaller branches, categorizing them into bifurcation and trifurcation groups.9,11) In the present study, MCA branching patterns were assessed by 2 experienced neurosurgeons (R.T. and Y.H.) using intraoperative digital subtraction angiography or postoperative imaging, including magnetic resonance angiography and computed tomography (CT) angiography. In cases where pre-stroke cerebral angiography had been performed, the imaging data were incorporated into the evaluation of the arterial branching patterns. Any disagreements were resolved by a third reader (M.A.), who has 25 years of experience in neurovascular imaging.
Statistical analysis
Categorical variables are presented as numbers and percentages, and continuous variables are presented as means ± standard deviations. The kappa coefficient was used to calculate interrater agreement for MCA branching patterns.
Fisher's exact test and the Mann-Whitney U test were performed to examine the significance of differences between MCA bifurcation and trifurcation patterns. Modified Poisson regression analyses were conducted to identify factors associated with successful recanalization, defined as mTICI ≥2b.13)
To adjust for confounders, we used causal-directed acyclic graphs (DAGs), diagrams composed of arrows and nodes that represent a system of causal relationships between measured or unmeasured variables in a study. DAGs guide confounding adjustments in standard regression models by explicitly depicting causal assumptions. We hypothesized causal relationships among variables based on previously published literature on successful recanalization (Supplementary Figure 1). Although it may be possible to draw different DAGs depending on causal assumptions, we considered this DAG to accurately capture the causal relationships among factors based on the known temporal ordering of the variables, existing literature, and clinical judgment. According to the assumptions in the DAG, we selected adjustment variables, including demographic characteristics, vascular risk factors, and the use of intravenous thrombolysis, to account for their potential impact on outcomes. The significance of differences between groups with and without successful recanalization was also examined in cases of M1 occlusion with the trifurcation type. Statistical analyses were performed with the JMP statistical package (version 16, SAS Institute, Inc.). Differences were defined as significant at a probability level of p < 0.05.
Results
The present study included 98 patients (mean age, 81 ± 11 years; 55 women), as detailed in the patient inclusion flowchart provided in Supplementary Figure 2. The mean ASPECTS of the study population was 6.0. The MCA branching pattern was assessable in all 82 patients with successful recanalization. Among the 16 patients without successful recanalization (mTICI ≤2a), the branching pattern was determined intraoperatively in 11 cases and preoperatively in 5 cases. In the 11 intraoperative cases, although distal M2 recanalization was not achieved, the MCA bifurcation anatomy could still be assessed during the procedure. Among the patients included, 21 (21%) exhibited a trifurcation pattern, while 77 (79%) had a bifurcation pattern on the affected side. Interrater agreement for evaluating MCA branching patterns was good (κ = 0.67, 95% confidence interval [CI] 0.50-0.84).
There were no significant differences in age, sex, medical history, the premorbid mRS score, or the use of intravenous thrombolysis between the trifurcation and bifurcation groups (Table 1). The ASPECTS was significantly lower in the trifurcation group than in the bifurcation group (5.0 ± 1.7 vs. 6.0 ± 2.2, p = 0.015). Patients in the trifurcation group were more likely to have trifurcations on the non-affected side compared with those in the bifurcation group (9 out of 21 [43%] vs. 8 out of 77 [10%], p = 0.004). Additionally, they exhibited a smaller diameter of the largest M2 branch in the affected MCA (1.7 ± 0.28 mm vs. 2.1 ± 0.34 mm, p < 0.001) and a larger bending angle between the M1 and M2 segments (108° ± 23° vs. 84° ± 26°, p < 0.001). The trifurcation group had a significantly lower rate of successful recanalization (12 out of 21 [57%] vs. 70 out of 77 [91%], p < 0.001), required 3 or more thrombectomy attempts (11 out of 21 [52%] vs. 15 out of 77 [19%], p = 0.005), and had a longer puncture-to-recanalization time (45 ± 28 mins vs. 27 ± 16 mins, p < 0.001) than the bifurcation group. Procedural complications, including intraoperative thrombus migration to distal vessels (13 out of 21 [62%] vs. 28 out of 77 [36%], p = 0.047) and symptomatic intracerebral hemorrhage (8 out of 21 [38%] vs. 11 out of 76 [14%], p = 0.027), were significantly more frequent in the trifurcation group than in the bifurcation group. There was no significant difference in the rate of good outcomes 90 days after MT between the trifurcation and bifurcation groups (7 out of 21 [33%] vs. 24 out of 77 [31%], p = 0.850).
Table 1.
Comparisons of Characteristics of MCA Bifurcation and Trifurcation Types
| Characteristics | Bifurcation (n = 77) | Trifurcation (n = 21) | p-Value |
|---|---|---|---|
| Baseline characteristics | |||
| Age (years) | 82 ± 10 | 78 ± 11 | 0.14 |
| Female, % | 44 (57) | 11 (52) | 0.81 |
| Medical history | |||
| Hypertension, % | 37 (48) | 9 (43) | 0.81 |
| Hyperlipidemia, % | 12 (16) | 2 (10) | 0.73 |
| Diabetes mellitus, % | 18 (23) | 6 (29) | 0.78 |
| Atrial fibrillation, % | 69 (90) | 17 (81) | 0.28 |
| ASPECTS | 6.0 ± 2.2 | 5.0 ± 1.7 | 0.015 |
| Pre-morbid mRS | 0.86 ± 1.4 | 0.95 ± 1.2 | 0.71 |
| Intravenous thrombolysis, % | 18 (23) | 4 (19) | 0.78 |
| Vascular anatomy | |||
| Trifurcation on the non-affected side | 8 (10) | 9 (43) | 0.004 |
| The largest M2 branch diameter (mm) | 2.1 ± 0.34 | 1.7 ± 0.28 | <0.001 |
| M1-M2 angle (°) | 84 ± 26 | 108 ± 23 | <0.001 |
| Procedural outcomes | |||
| Final successful recanalization (mTICI 2b-3), % | 70 (91) | 12 (57) | <0.001 |
| Total pass number | 0.009 | ||
| 1, % | 50 (65) | 4 (19) | |
| 2, % | 12 (16) | 6 (29) | |
| 3, % | 13 (17) | 9 (43) | |
| 4, % | 2 (3) | 2 (9.5) | |
| Last known well to recanalization time (min) | 423 ± 385 | 393 ± 339 | 0.78 |
| Puncture-to-recanalization time (min) | 27 ± 16 | 45 ± 28 | <0.001 |
| Intra-operative distal thrombus migration, % | 28 (36) | 13 (62) | 0.047 |
| Symptomatic intracranial hemorrhage, % | 11 (14) | 8 (38) | 0.027 |
| 90-day good outcome (mRS0-2), % | 24 (31) | 7 (33) | 1.0 |
Values are shown as numbers (%) or means ± SD unless otherwise indicated.
The boldface type indicates a significant difference (p < 0.05).
ASPECTS: Alberta Stroke Program Early Computed Tomography Score; mRS: modified Rankin Scale; mTICI: modified thrombolysis in cerebral infarction
Among patients with bifurcation-type occlusions, there was no significant difference in the rate of successful recanalization between cases where the microcatheter was introduced into the inferior versus superior M2 branches (53 out of 58 [91%] vs. 17 out of 19 [89%]; p = 1.00). Similarly, in patients with trifurcation-type occlusions, no significant difference in successful recanalization rates was observed among inferior, middle, and superior branches (3 out of 7 [43%] vs. 4 out of 6 [67%] vs. 5 out of 8 [63%]; p = 0.64).
A univariate modified Poisson regression analysis revealed that the MCA trifurcation pattern was associated with a significantly lower likelihood of successful recanalization (relative risk [RR] = 0.21; 95% CI, 0.09-0.50; p < 0.001) (Table 2). This relationship remained significant in the multivariate analysis, where the MCA trifurcation pattern was independently linked to a reduced likelihood of successful recanalization (RR = 0.22; 95% CI, 0.09-0.53; p = 0.001).
Table 2.
Univariate and Multivariate Modified Poisson Regression Analyses of Relationships Between MCA Branching Patterns and Successful Recanalization
| Risk ratios of successful recanalization | |||||
|---|---|---|---|---|---|
| MCA branching patterns | Univariate regression | Multivariate regression* | |||
| RR (95% CI) | p-Value | RR (95% CI) | p-Value | ||
| Bifurcation | Reference | ||||
| Trifurcation | 0.21 (0.09-0.50) | <0.001 | 0.22 (0.09-0.53) | 0.001 | |
Successful recanalization is defined as a modified Thrombolysis in Cerebral Infarction score of 2b-3.
The boldface type indicates a significant difference (p < 0.05).
*A multivariate modified Poisson regression analysis was adjusted for age, sex, hypertension, hyperlipidemia, diabetes mellitus, atrial fibrillation, and intravenous thrombolysis.
CI: confidence interval; RR: risk ratio
Among the 21 patients in the trifurcation group, successful recanalization with a single pass was achieved in 4 patients, while the remaining 17 required 2 or more attempts. Five of these 17 patients required a switch to contact aspiration after an unsuccessful initial attempt with the combined technique. This strategy significantly improved the rate of successful recanalization compared with repeated attempts using the combined technique (5 out of 5 [100%] vs. 3 out of 12 [25%], p = 0.0048). Furthermore, among the cases treated solely with the combined approach, we focused on the location of the AC tip within the vessel. Among the 17 cases, the position of the AC tip could not be evaluated in 2 cases due to the absence of intra-procedural imaging data. The rate of successful recanalization was significantly higher in the distal AC group compared with the proximal AC group (6 out of 9 [67%] vs. 0 out of 6 [0%], p = 0.0098). In contrast, among the 77 patients in the bifurcation group, the position of the AC tip could not be evaluated in 12 cases due to the absence of intra-procedural imaging data. The rate of successful recanalization was not significantly different between the distal and proximal AC groups (45 out of 51 [83%] vs. 14 out of 14 [100%], p = 0.33). Among procedure-related complications in the trifurcation group, no significant differences were observed between the distal and proximal AC groups in the rates of intraoperative distal thrombus migration (6 out of 9 [67%] vs. 4 out of 6 [67%], p = 1.0) or symptomatic intracerebral hemorrhage (3 out of 9 [33%] vs. 5 out of 6 [83%], p = 0.14). Representative cases are shown in Figures 1 and 2.
Figure 1.
A representative case illustrating the successful positioning of the AC tip at the proximal surface of the thrombus. (A) The left anteroposterior internal carotid artery angiogram revealed a thrombus in the distal M1 segment (white arrowhead), with the M2 inferior branch being visible. (B) The initial thrombectomy attempt, performed using a combined technique, encountered difficulty advancing the AC. Its tip failed to reach the proximal surface of the thrombus (white arrowhead). (C) A post-thrombectomy anteroposterior angiogram showed partial reperfusion, with a residual thrombus at the MCA bifurcation (white arrowhead). (D) During the second attempt, a contact aspiration technique was employed, successfully advancing the AC tip adjacent to the proximal surface of the thrombus (white arrowhead). (E) The final post-thrombectomy anteroposterior angiogram reveals successful recanalization, achieving a mTICI score of 2b. However, distal thrombus migration (white arrowhead) is noted in the M2 superior branch.
AC: aspiration catheter; MCA: middle cerebral artery; mTICI: modified Thrombolysis in Cerebral Infarction
Figure 2.
A representative case illustrating the failure of the AC tip to reach the proximal surface of the thrombus. (A) The left anteroposterior internal carotid artery angiogram showed a thrombus in the distal M1 segment (white arrowhead). (B) The initial thrombectomy attempt, performed using a combined technique, encountered difficulty in advancing the AC tip, which failed to reach the proximal surface of the thrombus (white arrowhead). (C) Post-thrombectomy anteroposterior angiogram demonstrating partial reperfusion, with persistent occlusion of the M2 inferior branch (white arrowhead). (D) A subsequent thrombectomy attempt, again utilizing a combined technique with the deployment of a stent retriever in the inferior branch, also failed to advance the AC tip to the thrombus (white arrowhead). (E) The final post-thrombectomy anteroposterior angiogram showed M2 inferior branch reperfusion. However, distal migration of the thrombus is noted in the M2 middle branch (white arrowhead). The outcome yielded a mTICI score of 2a.
AC: aspiration catheter; mTICI: modified Thrombolysis in Cerebral Infarction
Discussion
The present study investigated the impact of MCA branching patterns, specifically bifurcation and trifurcation, on procedural and clinical outcomes following MT. Additionally, we explored optimal MT strategies for managing M1 segment occlusions in patients with a trifurcation pattern. Our findings indicate that the trifurcation group had significantly lower rates of successful recanalization than the bifurcation group. Notably, within the trifurcation group, distal positioning of the AC tip was associated with a significantly higher rate of successful recanalization than proximal positioning without increased procedure-related complications. These results suggest that AC positioning is critical in optimizing MT outcomes for patients with complex MCA branching patterns.
We considered 3 possible reasons why the MCA trifurcation group had lower rates of successful recanalization than the bifurcation group. First, the largest M2 branch diameter was significantly smaller in the trifurcation type than in the bifurcation type (Table 1). A previous study also showed that the post-deployment stent diameter was significantly smaller in unsuccessful than in successful recanalization cases.14) This finding suggests that the lower recanalization rates observed in the trifurcation group were attributed to a reduced interaction between the stent struts and thrombus burden, likely caused by inadequate stent expansion within smaller-caliber vessels. Second, the trifurcation type exhibited a larger bending angle between the M1 and M2 segments than the bifurcation type. Previous clinical and in vitro studies demonstrated that larger M1/M2 angles correlated with unsuccessful recanalization (TICI 0-2a).4,5,15,16) When retracting the stent retriever through a vessel with a larger angle, the stent retriever may lose its full spatial extension, potentially reducing its grip and interacting forces on the thrombus. These vessel morphological characteristics associated with the trifurcation type may contribute to the lower rate of successful recanalization. Third, the increased number of MCA branches in the trifurcation type was associated with more thrombectomy attempts than in the bifurcation type. The present study revealed that cases requiring 3 or more passes were significantly higher in the trifurcation type than in the bifurcation type (53% vs. 20%, p = 0.005). Previous studies showed that thrombi retrieved in the first 2 passes were predominantly rich in red blood cells (RBC), whereas those retrieved after 3 or more passes were rich in fibrin.17) Fibrin-rich clots exhibit a higher coefficient of friction than RBC-rich clots, making them more resistant to retrieval. These findings underscore that the MCA trifurcation type is associated with more procedural passes, contributing to the increased difficulty of thrombus removal and lower rates of successful recanalization.
Despite differences in recanalization rates and procedural complications between the trifurcation and bifurcation groups, there was no significant difference in good clinical outcomes at 90 days post-MT. Several factors may explain this finding. Recent trials have reported that 50%-54% of patients undergoing EVT experience poor clinical outcomes despite achieving successful recanalization.1-3) This phenomenon, termed futile recanalization (FR), has been extensively studied. A meta-analysis identified multiple FR-related factors, including advanced age and the absence of intravenous thrombolysis.18) In the present study, the bifurcation group had an older average age (82 ± 10 years) and a lower rate of intravenous thrombolysis (23%), which may have contributed to a higher FR rate. These factors could have offset the potential clinical advantage of higher recanalization rates in the bifurcation group, ultimately leading to the observed lack of difference in clinical outcomes between the 2 groups.
In the present study, the rate of hemorrhagic complications following MT was relatively higher than that reported in previous studies.1) A plausible explanation for this finding is the lower baseline ASPECTS in our cohort compared with previous studies. Prior studies have demonstrated that lower ASPECTS is associated with an increased risk of symptomatic intracerebral hemorrhage after reperfusion therapy.19) Therefore, the higher frequency of hemorrhagic complications observed in our study is likely attributable, at least in part, to the inclusion of patients with larger infarct volumes at baseline.
The present study examined optimal MT strategies for managing MCA trifurcation types. We demonstrated that switching to contact aspiration after a failed initial combined technique resulted in a significantly higher successful recanalization rate than repeated attempts with the combined technique. Similarly, a recent study reported that converting to the contact aspiration technique following a failed combined approach increased the likelihood of successful recanalization and favorable functional outcomes without symptomatic intracerebral hemorrhage.20) However, that study did not elucidate the reasons for increased successful recanalization rates after switching to contact aspiration following the combined technique. We specifically examined the location of the AC tip within the vessel in trifurcation cases. In all 5 cases treated with contact aspiration after a failed combined technique, the AC tip was positioned in contact with the proximal side of the thrombus. Moreover, among the cases treated solely with the combined technique, the distal AC group achieved significantly higher recanalization rates than the proximal AC group (Figures 1 and 2). In contrast, the difference in successful recanalization rates between the distal and proximal AC groups was not statistically significant in bifurcation-type occlusions. Given the relatively small sample size in the trifurcation group (n = 21), the potential limitations in statistical power should be acknowledged. Nonetheless, our findings suggest that ensuring direct contact between the AC tip and the thrombus may be particularly critical for achieving successful recanalization in anatomically complex trifurcation cases. Recently, small-caliber ACs have become available, offering improved navigability into more distal branches.21) These catheters may enable more effective contact with the proximal end of the thrombus, potentially improving recanalization rates in anatomically challenging trifurcation cases.
The MCA branching pattern was assessable in nearly all cases, regardless of recanalization success, by referencing preoperative imaging and intraoperative angiographic records. Consistent with previous studies, the rate of the MCA trifurcation type was 21% in the present study, underscoring that the trifurcation type is a common anatomical variation in MCA occlusion cases.9,11) We demonstrated that the MCA trifurcation type was independently linked to a reduced likelihood of successful recanalization; however, the ability to predict MCA branching patterns remains unclear. We evaluated branching patterns on both the affected and non-affected sides, focusing on the symmetry of MCA branching. The results obtained showed that the affected side exhibited a bifurcation pattern in 90% of cases in which the non-affected side also had a bifurcation pattern, and a trifurcation pattern in 43% of cases in which the non-affected side also had a trifurcation pattern. Similarly, a previous study reported symmetrical MCA branching patterns in 92% of bifurcation cases and 57% of trifurcation cases.22) These findings show that assessments of branching patterns on the non-affected side may provide insights for predicting unvisualized MCA branching patterns. Alternatively, a recent study showed that intraoperative contrast-enhanced cone beam CT provided superior visualization of the distal thrombus and arterial branches compared with 3D rotational or digital subtraction angiography, potentially enhancing the efficacy of MT in MCA occlusions.23) However, a significant limitation of contrast-enhanced cone beam CT is the prolonged immobility required for image acquisition. Consequently, this method may be valuable for predicting MCA branching patterns on the affected side when MT is performed under general anesthesia.
Limitations
The present study has several limitations. As a single-center, retrospective study, it is subject to a selection bias. Confirmation of the results in larger, prospective cohorts is warranted and planned for future research. Furthermore, several factors, such as clot location and thrombus burden, were not evaluated, which may affect MT outcomes in MCA occlusion cases.4,8) Additionally, this study did not assess the relationship between clinical outcomes and the anatomical functionality of MCA branches in relation to cerebral territories. Characterizing the functional distribution of M2 branches in bifurcation and trifurcation patterns could provide valuable insight into clinical outcomes, particularly in cases of persistent occlusion. In addition, this study did not examine the relationships between successful recanalization and device characteristics, such as stent diameter or AC type.24) Furthermore, the experience levels of the operators, which may influence the choice of thrombectomy technique and the ability to guide the AC to the thrombus,25) were not assessed. Recent advances in MT have led to the development of various strategies for managing complex arterial occlusions. One such strategy is the use of double stent retrievers, which has demonstrated potential for enhancing clot engagement and retrieval efficiency.26,27) Another promising approach involves the EmboTrap III, a stent retriever with a distinctive structure comprising a collapsible outer cage and an inner channel.28) When a thrombus is lodged at an arterial bifurcation, this device may encapsulate the clot during retrieval, thereby facilitating complete recanalization. Further studies are warranted to evaluate the relative efficacy of these techniques in improving thrombectomy outcomes in patients with trifurcation-type occlusions.
Conclusion
Trifurcation anatomy hindered effective clot engagement by the AC due to narrow M2 diameters and large branching angles, often resulting in lower successful recanalization rates than those observed in bifurcation anatomy.
Author Contributions
R.T. and Y.H. drafted the main manuscript and prepared all tables and figures.
M.A., R.T., and Y.H. collected the clinical and imaging data.
R.K. performed the statistical analyses.
N.H performed supervision.
All authors critically reviewed the manuscript and approved the final version.
Conflicts of Interest Disclosure
All authors have no conflict of interest.
Data Availability
The supporting data of this study is available from the corresponding author on reasonable request.
Ethics Approval and Consent to Participate
The present study was approved by the local Institutional Review Board (OJH-202410). Patients' informed consent was not required because this study was non-invasive and retrospective.
Clinical Trial Number
Not applicable.
Supplementary Material
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The supporting data of this study is available from the corresponding author on reasonable request.