Introducing the Caliber-Flow Status Scale (CFSS): a novel tool for assessing covered cortical branch status after flow diverter treatment of middle cerebral artery aneurysms

Abstract

Background

This study assessed caliber and flow changes of covered cortical middle cerebral artery (MCA) branches using the new Caliber-Flow Status Scale (CFSS), postoperative diffusion-weighted imaging (DWI) lesions, and clinical outcome following flow diverter (FD) treatment of MCA aneurysms.

Methods

This single-center retrospective study collected data from patients treated with FD between January 2016 and March 2024, including patient characteristics, aneurysm features, postoperative DWI lesions, and clinical outcomes. Vessel status was assessed using CFSS: 1a (normal caliber and flow), 1b (normal caliber, reduced flow), 2a (reduced caliber, normal flow), 2b (reduced caliber and flow), and 3 (occlusion).

Results

Thirty-nine patients with 41 aneurysms with 63 covered MCA branches were included. Immediately after FD deployment, 63.5% of covered branches retained normal caliber and flow (CFSS 1a) while the remaining branches with compromised caliber and flow (CFSS >1a) showed significant improvement following tirofiban administration. Intraoperative thromboembolic complications led to occlusion in three branches, all restored after tirofiban without clinical symptoms (P=0.003). At 6 months, 79% of covered branches showed normal flow with or without caliber reduction (CFSS 1a/2a). DWI lesions showed no significant correlation with caliber and flow changes and clinical symptoms.

Conclusions

FD treatment for MCA aneurysms leads to significant but primarily asymptomatic CFSS changes in covered cortical branches within the first 6 months. Intra-arterial tirofiban effectively improves vessel status in branches with higher CFSS (>1a). CFSS is valuable for tracking these changes and underscores the importance of long-term follow-up.

WHAT IS ALREADY KNOWN ON THIS TOPIC

• The use of flow diverters (FDs) for embolization in middle cerebral artery (MCA) aneurysms remains debatable due to concerns about the safety of covered MCA branches, given the potential for flow reduction or occlusion in these vessels.

WHAT THIS STUDY ADDS

• This study introduces the newly developed Caliber-Flow Status Scale (CFSS), demonstrating measurable branch caliber and flow changes for covered cortical branches following FD embolization of MCA aneurysms.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• The CFSS offers a valuable tool for assessing branch changes and should be integrated into FD treatment for MCA aneurysms to help evaluate treatment outcomes and long-term vascular remodeling.

Introduction

Middle cerebral artery (MCA) aneurysms often present with unfavorable anatomy, characterized by a wide neck and the incorporation of branching vessels at the bifurcation or neck.¹ These characteristics pose significant challenges for conventional endovascular approaches, including coiling, stent-/ballon-assisted coiling, and flow disruption.^{2 3} Recent studies have reported the use of flow diverter (FD) embolization in MCA aneurysms, with relatively high morbidity rates (6.7–9.2%) and mortality rates (up to 2.0%).^{4 5} Despite generally high aneurysm occlusion rates,^{4 5} the safety of FD embolization remains controversial as it potentially leads to a reduced blood flow or complete vessel occlusion of covered branches.^{6 7} Branch coverage following flow diversion has been analyzed in the internal carotid artery (ICA) and anterior communicating artery (ACom), with most studies showing asymptomatic flow alterations and caliber modifications.^{8 9} However, there is limited systematic analysis of caliber and flow changes of the covered MCA branches after FD placement in MCA aneurysms,59,11 leaving this area of branch evolution poorly understood.

This study analyzed the semiquantitative angiographic evolution of covered cortical MCA branches using a newly developed 5-point combined Caliber-Flow Status Scale (CFSS) to systematically assess the relationship between covered branch patency and occlusion rates by evaluating the caliber and flow changes. Additionally, we assessed the correlation between these changes and diffusion-weighted imaging (DWI) lesions on postoperative MRI, as well as the clinical evolution between the postoperative status and the 6- and 12-month follow-up.

Methods

Study design

This single-center retrospective study included patients aged >18 years treated with FD for MCA aneurysms at the Centre Hospitaller Universitaire de Reims between January 2016 and March 2024 (figure 1). The study was approved by the Comité d’Ethique pour la Recherche en Imagerie Médicale of Collège des Enseignants de Radiologie de France (CRM-2411–435) and written informed consent was waived. We used the STROBE cross-sectional checklist when writing our report.¹²

Figure 1. Flowchart of patient selection criteria for flow diverter treatment in middle cerebral artery (MCA) bifurcation aneurysms.

Interventional procedure

Preoperative dual antiplatelet treatment (DAPT) consisted of 75 mg acetylsalicylic acid (ASA) and 180 mg ticagrelor administered for 2 days prior to the procedure. All procedures were performed under general anesthesia using a biplane angiographic system (Azurion ClarityIQ; Philips Healthcare, Best, The Netherlands) with systemic heparinization and triaxial access. Only patients treated with a single FD were included. All FDs were normosized to match the parent artery diameter according to manufacturer guidelines. Oversizing was avoided to minimize flow disturbances in adjacent branches. Final FD placement and wall apposition were confirmed with digital subtraction angiography (DSA) and Flat-Panel CT.

Four different types of commercial FDs were implanted: p48 (first generation p48, p48 MW, p48-MW-HPC)/p64 (first generation p64, p64 MW, p64-MW-HPC; Phenox, Bochum, Germany); Silk FD (Silk, Silk Vista, Silk Vista Baby; Balt, Montmorency, France); FRED (FRED, FRED Jr; MicroVention, Aliso Viejo, California, USA); and Pipeline Flex (Medtronic, Dublin, Ireland).

Data collection

Data collected for each patient included age, gender, preoperative and postoperative antiplatelet regimen, total number of intracranial aneurysms, aneurysm characteristics (location, diameter, height, neck size, and dome-to-neck ratio), and aneurysm status (unruptured, ruptured, and recanalized). Data obtained related to the procedure included treatment date; type of FD used; technical issues during FD deployment (including fish mouthing); occurrence of intraoperative thromboembolic and hemorrhagic complications; intra-stent balloon angioplasty use; adjunctive device use; and administration of IA tirofiban (1 mg).

Aneurysm occlusion status was evaluated at procedure end, 6 months, and 12 months using DSA.

Postoperative MRI was performed within 48 hours to assess DWI lesions in the MCA territory. Clinical status was evaluated preoperatively, postoperatively at 1 month, and at 12 months using the modified Rankin Scale (mRS). Morbidity was defined as mRS ≥3.

Follow-up protocol

The follow-up regimen included an MRI within 48 hours post-procedure and simultaneous MRI and DSA at 6 months and 12 months. All MRIs were performed on a 3T scanner (Skyra; Siemens, Erlangen, Germany) using a 64-element head coil. DSA was performed using transfemoral catheterization with selective series and IA Flat-Panel CT in standard projections.

Image evaluation

Two independent readers with over 5 years of neurointerventional experience reviewed the angiographic images.

Caliber and flow dynamics of the covered cortical vessels were assessed. Caliber was measured at 0 (pre-deployment, immediate post-deployment, and final post-deployment DSA run), 6 months, and 12 months using two-dimensional anteroposterior DSA images. Arteries were measured at the maximum diameter distal to the FD. To ensure consistency across images, measurements were normalized by adjusting for any percentage difference attributable to variations in the field of view using the diameter of the vertical petrous ICA segment as reference. Vessel caliber was categorized as 1=stable size and 2=reduction in size. Flow dynamics were classified simultaneously as a=normal arterial flow and b=decreased velocity with only slow arterial flow.¹¹ The CFSS was designed to categorize branch status and also to analyse the changes in caliber, flow, and the likelihood of branch occlusion at 6- and 12-month follow-up intervals. Table 1 shows the combined assessments forming the CFSS.

Table 1. Caliber-Flow Status Scale (CFSS).

Caliber-Flow Status Scale
1a	Normal caliber with normal flow
1b	Normal caliber with slow flow
2a	Reduced caliber with normal flow
2b	Reduced caliber with slow flow
3	Occlusion

Postoperative DWI lesions in the ipsilateral MCA territory were classified into five categories to provide a semiquantitative measure of the lesion burden: 1 (0–5 lesions), 2 (6–10 lesions), 3 (11–15 lesions), 4 (16–20 lesions), and 5 (>20 lesions), and correlated with clinical symptoms. This DWI stratification balances clinical relevance and precision, allowing identification of trends without overly fragmenting the data.

Statistical analysis

Quantitative variables were described as mean±SD while qualitative variables were presented as numbers and percentages. Given that not all data followed a normal distribution, the Wilcoxon test for paired samples was used and the χ² test was applied for categorical variables. Spearman’s rank correlation coefficient was used to assess the statistical correlation between variables. P values <0.05 were considered statistically significant. Statistical analyses were performed using MedCalc Software, V.22.007 (University of South Carolina, Columbia, South Carolina, USA).

Results

Patient and aneurysm characteristics

Table 2 shows the baseline characteristics of the 39 patients with 41 aneurysms (with 41 procedures).

Table 2. Baseline descriptive statistics.

Variable	N (%)
Mean age (range) (years)	57±11* (25–81)
Gender
Female	28/39 (71.8%)
Male	11/39 (28.2%)
Total intracranial aneurysms
1	24/41 (58.5%)
>1	17/41 (41.5%)
Preoperative mRS (per patient)
0–2	37/39 (94.9%)
3–5	2/39 (5.1%)
Postoperative mRS at 12 months (per patient)
0–2	29/31 (93.6%)
3–5	1/31 (3.2%)
6†	1/31 (3.2%)
Aneurysm status
Unruptured	33/41 (80.5%)
Ruptured‡	1/41 (2.4%)
Recanalized	7/41 (17.1%)
Aneurysm size (maximum diameter)§
<5 mm (small)	8/41 (19.5%)
5–10 mm (medium)	25/41 (60.0%)
11–25 mm (large)	8/41 (19.5%)
Aneurysm diameters, mm
Maximal diameter	7.8±3.8*
Height	5.3±2.7*
Neck width	5.2±2.4*
Dome-to-neck ratio	1.2±0.4*

^*Mean±SD.

^†Patient died 10 months post-procedure due to intracranial trauma following a motor vehicle accident.

^‡Wide-neck shallow microaneurysm that was not amenable to treatment with other endovascular approaches.

^§According to the The Natural Course of Unruptured Cerebral Aneurysms in a Japanese Cohort (UCAS) stratification.20

mRS, modified Rankin Scale.

Among the seven recanalized aneurysms, two were previously treated with coil embolization, one with coiling followed by clipping, one with stent-assisted coiling, two with WEB embolization, and one with clipping.

The distribution of FD types was as follows: nine Silk FDs (22.0%; Silk: 3, Silk Vista: 3, Silk Vista Baby: 3); one Pipeline Flex FD (2.4%); five FRED FDs (11.9%; FRED: 1, FRED Jr: 4); 11 p64 FDs (26.2%; p64: 2, p64 MW: 2, p64 HPC: 7); and 14 p48 FDs (34.1%; p48: 2, p48 MW: 6, p48 HPC: 6). Adjunctive coils were deployed in 16/41 (39.0%) procedures and an additional WEB device in 4/41 (9.8%) procedures. A total of 38/41 aneurysms (92.7%) were treated with direct neck coverage and flow diversion. In the remaining three aneurysms (7.3%) the FD did not directly cover the aneurysm neck, resulting in indirect flow diversion.

Intra-stent angioplasty was performed using either a TransForm compliant balloon (Stryker Neurovascular, Kalamazoo, Michigan, USA) or Eclipse (Balt, Montmorency, France) in 3/41 (7.3%) procedures due to proximal fish mouthing and in 2/41 (4.9%) procedures due to insufficient wall apposition.

Postoperative antiplatelet regime

Thirty-four of the 39 patients (87.2%) received standard postoperative DAPT consisting of ticagrelor (90 mg twice daily) and ASA (75 mg daily) for 3 months, followed by 9 months of ASA monotherapy. The remaining five patients (12.5%) had varied ticagrelor and ASA regimens due to in-stent stenosis and ischemic events, including ticagrelor monotherapy for 6 months in one patient; ticagrelor plus ASA for 6 months followed by ASA monotherapy for another 6 months in one patient; ticagrelor monotherapy for first 6 months followed by ASA monotherapy for another 6 months in two patients; and ticagrelor plus ASA for 6 months followed by lifetime ASA in one patient. A non-compliance issue was noted in one patient who missed a single dose of ticagrelor at 1 month.

Anatomical results

Immediate post-deployment DSA images were available for all patients, showing complete aneurysm occlusion in 5/41 procedures (12.2%) and aneurysm remnants in 36/41 procedures (87.8%). The mean timing for the first and second DSA follow-up was 6.4±0.9 months and 13.2±2.5 months, respectively. At 6-month follow-up, DSA was available in 34/41 aneurysms (82.9%), when 21 aneurysms (61.8%) showed complete occlusion while 13 (38.2%) had aneurysm remnants (no neck remnants were observed). At 12-month follow-up, DSA was available for 26/41 (63.4%) aneurysms, when 20 aneurysms (76.9%) showed complete occlusion, five (19.3%) with aneurysm remnants, and one (3.8%) with neck remnants.

Angiographic evaluation of covered cortical MCA branches by the CFSS

The Wilcoxon test was used to calculate P values for covered branch status changes at different time points (table 3).

Table 3. Covered branch outcomes.

No of branches	Pre-FD	Immediate post-FD	Final post-FD	6 months	12 months	Pre-IA tirofiban	Post-IA tirofiban	Thromboembolic complications
	63	63	63	43	38			Peri-procedure	<1 month	>1 month
CFSS
1a	63 (100%)	40 (63.5%)	45 (71.4%)	11 (25.5%)	11 (28.9%)	–	8 (47.0%)	–	–	1*
1b	–	3 (4.8%)	1 (1.6%)	–	–	3 (17.6%)	1 (5.9%)	–	–	–
2a	–	12 (19.0%)	16 (25.4%)	23 (53.5%)	20 (52.6%)	6 (35.4%)	7 (41.2%)	–	1*	–
2b	–	5 (7.9%)	1 (1.6%)	6 (14.0%)	5 (13.2%)	5 (29.4%)	1 (5.9%)	1*	–	–
3	–	3 (4.8%)	–	3 (7.0%)	2 (5.3%)	3 (17.6%)	–	3	–	–
P value		<0.001	0.044	<0.001	0.636	0.003

^*Symptomatic thromboembolic events.

CFSS, Caliber-Flow Status Scale; FD, flow diverter.

CFSS evolution of covered branches after IA tirofiban administration

Among 63 covered branches, 40 (63.5%) retained both normal caliber and flow immediately following FD deployment (CFSS 1a). Of the remaining 23 branches, three (4.8%) had normal caliber with slow flow (CFSS 1b), 17 branches showed reduced caliber with 12 branches (19.0%) maintaining normal flow (CFSS 2a), while five branches (7.9%) showed reduced flow (CFSS 2b). Three branches (4.8%) were occluded (CFSS 3).

IA tirofiban (1 mg) was administered in 12 patients to 17 covered branches initially graded as CFSS >1a. Of the three branches with an initial CFSS 1b, two improved to CFSS 1a. Similarly, 2/6 branches initially graded as CFSS 2a returned to CFSS 1a while 4/5 branches with CFSS 2b improved to either CFSS 1a or 2a. All three branches that were initially occluded (CFSS 3) showed substantial recovery, with flow restored to either CFSS 1a or 2a (P=0.003). None of the covered branches with CFSS 1a received IA tirofiban. Figure 2 shows CFSS changes for covered MCA branches in a patient following FD treatment.

Figure 2. A patient treated with a flow diverter in the superior middle cerebral artery (MCA) branch, covering the inferior MCA branch, a smaller side branch of the superior MCA, and the anterior temporal artery (ATA). (A) Pre-deployment DSA shows Caliber-Flow Status Scale (CFSS) 1a for all covered branches. (B) Immediate post-deployment DSA shows CFSS 2b for the inferior MCA branch, 1a for both the side branch of the superior MCA and the ATA. (C) After IA administration of tirofiban, final DSA shows CFSS 1a for the inferior MCA branch, side branch of the superior MCA and 2a for the ATA. (D) Six-month follow-up DSA shows CFSS 1a for the inferior MCA branch and ATA, with CFSS 2a for the side branch of the superior MCA.

Peri- and post-procedural complications

Thromboembolic complications leading to branch occlusion (CFSS 3) occurred in three cases. All three cases successfully reopened with 1 mg IA tirofiban and remained clinically asymptomatic, while one patient with an initial CFSS of 2b in a covered non-cortical branch that did not improve post-tirofiban developed a stroke unrelated to cortical branch coverage of the FD, and recovered to an mRS score of 1 within 1 month. No peri-procedural hemorrhagic complications or procedure-related mortality were observed.

Two cases of delayed FD occlusion were reported. The first case, with a final CFSS of 2a post-FD deployment, developed occlusion <1 month postoperatively, requiring mechanical thrombectomy, and resulted in an mRS score of 2 at 12 months. The second case, with a final CFSS of 1a, had delayed FD occlusion at >1 month and was also successfully treated with mechanical thrombectomy, with the patient achieving a mRS score of 1 at 12 months.

DWI lesions in the MCA territory on postoperative MRI

Postoperative MRI was available for 40/41 procedures (97.6%). One MRI showed no DWI lesions (2.4%), most DWI changes (32/40, 80.0%) were classified in category 1 (22/40, 55.0%) and category 2 (9/40, 22.5%), while the remaining nine patients were classified in category 3 (6/40, 15.0%), category 4 (2/40, 5.0%), and category 5 (1/40, 2.5%).

Only four patients with DWI lesions had postoperative neurological impairment. Three of these patients, all with a final post-FD deployment CFSS of 1a, fully recovered within 24 hours (mRS 0). The fourth patient, who had a final post-FD deployment CFSS of 2b in one covered non-cortical branch, had an mRS of 1 at 1 month. There was no correlation between DWI lesions and immediate post-deployment CFSS status of covered branches (P=0.585, Spearman’s rho 0.070) or final CFSS status (P=0.483, Spearman’s rho 0.089).

CFSS evolution of covered cortical MCA branches at 6- and 12-month follow-up

At 6-month follow-up the CFSS of covered cortical MCA branches showed a significant change compared with the immediate post-deployment status (P<0.001), with 23 covered branches (53.5%) showing caliber reduction without flow compromise (CFSS 2a), six (14%) with CFSS 2b, and three were occluded (CFSS 3). At 12 months no further significant differences were observed compared with the 6-month status (P=0.636), with 20 branches (52.5%) with CFSS 2a, five (13.2%) with CFSS 2b, and only two with CFSS 3.

Discussion

This study evaluated vessel caliber and flow status in covered cortical MCA branches combined with postoperative DWI lesions to assess clinical outcomes following FD treatment. Post-FD deployment, 63.5% of covered branches retained normal caliber and flow (CFSS 1a), while branches with higher CFSS grades showed significant recovery after IA tirofiban administration. Importantly, no significant correlations were found between DWI lesions and CFSS grade, suggesting that vessel caliber and flow changes are largely independent of immediate ischemic events. To our knowledge, this is the first study to precisely assess branch changes post-FD deployment through a combined CFSS and DWI imaging analysis.

CFSS development, impact, and results

The creation of CFSS provides a valuable tool for understanding the branch status following FD deployment because it uniquely integrates both caliber and flow changes to categorize branches into five distinct scales. This scale enabled precise tracking of post-procedural outcomes and provided a systematic approach to analyze vessel caliber and flow dynamics.

Our analysis showed that 36.5% of covered branches had a CFSS >1a (indicating altered caliber, flow, or both) immediately after FD deployment. IA tirofiban administration significantly improved vessel status, with 88.2% (15/17) of these branches recovering to CFSS 1a or 2a. Between the final post-deployment assessment and 6-month follow-up the primary change observed was a reduction in the caliber of 67.5% of covered branches, although flow remained unaffected in most cases (CFSS 2a, 53.5%; CFSS 2b, 14.0%). No further significant degradation was noted between 6 and 12 months, indicating probable vascular stabilization following the initial hemodynamic response induced by the FD. By 6 months, the adaptation of intracranial circulation to altered hemodynamics after FD placement (including progressive aneurysm occlusion and branch caliber adjustments) appear to plateau, marking the end of the acute hemodynamic phase.⁹ This finding can potentially impact the timing of follow-up, knowing that it is also dedicated to the evaluation of aneurysm occlusion and potential in-stent stenosis. Additionally, our data also show that the CFSS status at the end of the index procedure cannot predict the CFSS outcome at 6 or 12 months.

Flow diversion induces hemodynamic shifts that primarily affect covered branches, likely driven by increased resistances⁹ and a decreased blood flow.^{9 10 13} Specific anatomical features such as a large jailed artery size or an acute branch takeoff angle may contribute to clinically significant alterations in blood flow across jailed arteries and must be further analyzed.⁶ Further contributors to flow alterations including acute branch occlusion may be influenced by the systemic blood pressure, antiplatelet compliance, and procedural factors such as catheter manipulations and device repositioning. This, however, remains an issue for future investigations.

Comparison with previous studies

Our findings align favorably with recent literature reporting branch occlusion rates of 10.1–20% following FD treatment of MCA aneurysms.^{5 9 11} While branch coverage can lead to caliber and flow changes, our findings align with other studies that show asymptomatic flow modifications, particularly in regions such as the A1 segment in ICA aneurysm treatment.⁸ Michelozzi et al reported that, in MCA and ACom aneurysms, 13% of covered branches showed significant size reduction and 10% progressed to complete occlusion at 6 months. These results remained consistent at 12 months, with most cases being asymptomatic, although a few patients experienced mild motor deficits depending on the branch involved.⁹

Thromboembolic complication management and clinical outcomes

The risk of intraoperative thromboembolic complications during FD embolization is a significant concern, with reported rates reaching up to 14.9%.¹⁴ In our study we observed 6.2% of intraoperative thromboembolic events. The use of tirofiban during FD treatment is gaining recognition as a potential adjunctive treatment to manage thromboembolic complications.^{15 16} While not yet a standard, recent studies suggest that tirofiban can effectively mitigate the risk of branch occlusions that occur post-FD deployment¹⁵; however, it has not been uniformly administered in cases of post-deployment flow diminution in other studies.^{9 11 13} The antiplatelet properties of tirofiban help to maintain branch patency by preventing or resolving thrombus formation, which is crucial, especially when flow disrupts around covered branches.^{15 16} In our study, IA tirofiban (1 mg) administration was preferred due to the superselective nature of the cannulation, ensuring rapid and highly localized drug delivery to the targeted vessels. The administration of tirofiban significantly improved CFSS grades (P=0.003) in 17 covered cortical branches with post-FD flow impairment, thrombus formation, or occlusion, supporting its efficacy in MCA aneurysm treatment with flow diversion.

Implications for DWI

DWI lesions were frequently detected in postoperative MRI following FD deployment; however, our analysis found no significant correlation between DWI lesions and the CFSS. Despite the high incidence of DWI lesions, only a small subset of cases (4/41, 9.8%) showed neurological impairment. This discrepancy indicates that most DWI lesions are clinically silent, potentially due to their small size or occurrence in non-eloquent brain regions. These findings are consistent with other studies reporting similar high rates of DWI lesions following endovascular treatment of unruptured aneurysms without corresponding clinical symptoms.^{17 18}

The occurrence of DWI lesions following FD deployment can generally be considered multifactorial, and distinguishing between embolic and flow-related mechanisms is challenging. Procedural factors, including catheter manipulations, the number of device deployment attempts, and the duration of the procedure, can contribute to the generation of periprocedural microemboli. Additionally, flow-related mechanisms such as transient reductions in branch perfusion caused by the metal coverage of the FD could contribute to ischemic events. However, our lack of association suggests that embolic mechanisms may predominate in the formation of DWI lesions, rather than direct flow alterations or branch stenosis.

Technical considerations

The decision on FD deployment is crucial due to the unique anatomy of MCA aneurysms, particularly when covering branching vessels.⁵ Common complications include peri-procedural thrombus formation, in-stent thrombosis, and side branch occlusion.⁹ In our center we avoid covering the dominant MCA branch (typically the superior branch) which supplies the central region. Furthermore, differences in FD design such as braid count and mesh density may influence branch patency; however, subgroup analysis was not feasible due to sample size limitations. For aneurysms arising distal to the MCA bifurcation or involving peripheral segments, indirect flow diversion may be an appropriate strategy.¹⁹ Schob et al found that indirect FD is safe and feasible for off-center bifurcation and distal small aneurysms,¹⁹ although this approach was applied to only three of the 41 aneurysms (7.3%) in our study.

Limitations

This study has several limitations. First, our analysis was based on a relatively small, retrospective, single-center dataset with only 6- and 12- month follow-up DSA. Second, we focused our analysis on the covered cortical branches and excluded lenticulostriate branches which were outside the scope of this study. The technical limitation to evaluate lenticulostriate branch alterations and correlated DWI lesions lies in their natural small caliber, therefore this is an issue that needs separate evaluation. Third, DAPT was discontinued at 3 months without simultaneous DSA; thus, we cannot determine if branch adaptations were already stabilized at that time. Fourth, it must be noted that a reliable correlation between the location of DWI lesions within the MCA territory and the covered branches could not be established. The use of dedicated software to superimpose DSA and MRI images could facilitate more precise correlation between vascular changes and DWI lesions. Fifth, we did not analyze collateral circulation status because a standardized approach is challenging and quantification would be more reliable with advanced perfusion imaging techniques.

Conclusion

FD embolization shows promise as an alternative treatment for MCA aneurysms, largely preserving normal flow in covered branches and remaining asymptomatic in most cases. Administration of IA tirofiban effectively improves vessel status in branches with higher CFSS scores. Long-term follow-up is essential to confirm these benefits and monitor for late complications, while further research with larger randomized studies is required to validate these findings.

Data availability statement

Data are available upon reasonable request.