Mechanical thrombectomy for middle cerebral artery M2 occlusions

Abstract

Background

The safety and efficacy of mechanical thrombectomy (MT) for proximal large vessel occlusion after acute ischemic stroke (AIS) have been demonstrated. Clinical investigations of endovascular approaches for treating AIS due to M2 occlusions have been ongoing.

Purpose

To assess the outcomes of M2 occlusions according to treatment modality and anatomical division.

Methods

A total of 113 consecutive M2 occlusions treated with endovascular treatment (EVT) at our tertiary stroke center between January 2019 and December 2022 were retrospectively analyzed. Patients were divided into three groups: mechanical thrombectomy (MT); intravenous thrombolysis plus MT (IVT + MT); and IVT alone. The primary outcomes were good prognosis (mRS = 0–2) and mortality (mRS = 6) on day 90. The secondary outcome was to determine the differences in outcomes between lesions in the superior and inferior branches of M2.

Results

In total, 55 (48.7%) patients underwent MT. In 42 (37.2%) patients, bridging IVT was performed with MT, and IVT alone was applied in 16 (14.2%) patients. Neither the prognosis at 90 days nor the mortality rate significantly differed among the groups. The outcomes did not significantly differ between occlusions in the superior and inferior branches of M2.

Conclusion

MT was found to be safe and effective for treating M2 occlusions in this series.

Keywords

Endovascular treatment M2 occlusion stroke

Introduction

After mechanical thrombectomy (MT) has been recommended as a class 1A treatment modality (1) for acute occlusions of the proximal parts of large vessels (internal carotid artery, M1 segment), studies investigating the benefit of MT for more distal occlusions (M2, A2, M3) have been published (2 –5).

M2 occlusions account for approximately 20%–41% of anterior circulation strokes, and intravenous thrombolysis (IVT) is the most widely used method for achieving reperfusion (2,6). However, more than 50% of M2 occlusions that involve intravenous tissue plasminogen activator (IV tPA) are occluded and have a poor prognosis (2,7). With the development of small-stent retrievers (CatchView mini, “baby” Trevo, Tiger-13) and smaller aspiration catheters (3 MAX), there is increasing interest in MT for M2 occlusions (5). Furthermore, adjunctive local intra-arterial thrombolysis can increase the chance of better outcomes (8).

Another point to keep in mind is that the M2 segment is divided into superior and inferior divisions, and each division supplies different parts of the cerebral hemisphere. The presentation and technical and clinical outcomes can vary according to the affected area (frontal, sulcal, or parietotemporal region, or dominant or non-dominant hemisphere) and occluded vessel properties (smaller diameter, thinner walls, increased tortuosity, acute angle between M1 segments) (5,7,9).

The aim of the present study was to assess the outcomes of M2 occlusions according to treatment modality and anatomical division.

Material and Methods

Patient population

The present study was approved by Fatih Sultan Mehmet Training and Research Hospital Ethics Committee (approval no. 27.1.22/17). This study was conducted in accordance with the principles of the Declaration of Helsinki. Patients who underwent endovascular treatment (EVT) between January 2019 and December 2022 at the neurology department of a tertiary stroke center and who had acute occlusion of M2 were included. Demographic data were obtained from the hospital and the national health registry. Age, sex, co-morbidities, time of onset at admission, and initial stroke severity were recorded. Treatment methods were grouped as mechanical thrombectomy (MT), intravenous thrombolysis plus MT (IVT + MT), or IVT alone. The inclusion criteria were patients aged ≥18 years, patients who underwent non-contrast computed tomography (CT) or CT angiography at the time of admission, patients with M2 occlusion, and those with neurological deficits ≥1 according to the National Institutes of Health Stroke Scale (NIHSS). Patients with tandem occlusions were excluded.

Treatment methods

IVT was initiated in all eligible patients. Patients had NIHSS scores <6 and modified Rankin scale (mRS) scores >2 and received only IVT. For patients who received IVT, the t-PA dosage was 0.9 mg/kg, with a maximum dose of 90 mg over 1 h. Patients underwent MT without waiting for the effect of IVT.

Definitions of outcomes

The primary functional outcomes were good prognosis (mRS 0–2) and mortality (mRS 6) on day 90. Patients were seen during their routine clinical check-up in the outpatient setting or were reached by telephone. The secondary functional outcome was to define the prognosis of strokes associated with different M2 segment divisions (superior, inferior, or both). The M2 segment was defined as the perpendicular portion of the MCA in the sylvian fissure. The occlusion site was determined on initial imaging and verified via digital subtraction angiography (DSA) when available. The safety outcome was the absence of symptomatic intracranial hemorrhage (sICH). In general, sICH was defined as a new intracranial hemorrhage associated with an increase in the NIHSS score (>4 points) from the score immediately before the exacerbation. Hemorrhage was graded according to the method used in the European Cooperative Acute Stroke Trials. The NIHSS score at admission and at 24 h was used to assess the severity of neurological deficits. Successful recanalization was defined as expanded thrombolysis according to the Cerebral Ischemia Scale (eTICI) = 2c-3. Only three patients had a TICI of 2b-3; therefore, we preferred successful recanalization via the eTICI. The first-pass effect (FPE) was defined as achieving complete recanalization with a single thrombectomy device pass. Modified FPE (mFPE ≥ 2b) was not analyzed. Asymptomatic intracranial hemorrhage (aICH), subarachnoid hemorrhage, embolization (distal/new territory), malignant infarction, and decompression were also analyzed in the present study. Malignant infarction was defined as a large space-occupying infarction involving massive edema, herniation, or frequent death (10).

EVT procedures

All procedures were performed under regional anesthesia. Written informed consent was obtained from each patient or from their legal representatives for all diagnostic and therapeutic procedures.

Stent retriever (SR)-based thrombectomy was our choice for the majority of patients with M2 occlusions. Either a single SR with a balloon guiding catheter (BGC) or a combined technique with an aspiration catheter, depending on the ICA anatomy, was used for endovascular treatment. A 5-F Sofia aspiration catheter was the choice for the ADAPT technique. If FPE was not achieved, the second attempt was performed with the same material and technique. If the recanalization was still not successful, the technique and the material were changed. In the case of distal embolism, thrombectomy was performed with a low-profile stent retriever (CatchView Mini; Balt USA, Irvine, CA, USA). The number of SR attempts was generally limited to four.

Statistical analysis

For descriptive statistics, the mean ± standard deviation were used to present continuous data with a normal distribution. The median, along with the minimum and maximum values, was used to present continuous variables without a normal distribution. Categorical variables are presented as numbers and percentages. The normality of the numerical variables was tested using the Shapiro‒Wilk, Kolmogorov‒Smirnov, and Anderson‒Darling tests.

Pearson’s chi-square test and Fisher's exact test were used to compare the differences between categorical variables in 2 × 2 tables. The Fisher–Freeman Halton test was used for the RxC tables.

The Mann‒Whitney U test was used to compare two independent groups of normally distributed numerical variables.

For variables without a normal distribution, the Kruskal‒Wallis test was applied. When non-parametric tests were used, differences between the groups were evaluated with the Dwass-Steel-Critchlow-Fligner test.

Statistical analyses were performed using Jamovi (version 2.3.24.0) and JASP (version 0.17.1). The significance level (P value) was set at 0.05 for all the statistical analyses.

Results

The present study included 113 patients (51.0% men, 49.0% women; mean age = 72.7 ± 15.1 years). Hypertension was the most common co-morbidity and was observed in 85 (75.2%) patients. Although 29 (25.7%) patients were admitted to the hospital within the first hour after the onset of symptoms, 35 (31.0%) patients were admitted within 270 min. The mRS score at admission was zero for 81 (71.7%) patients and 1 for 27 (23.9%) patients. The median NIHSS score at admission was 11 (range = 1–23) in the study group. Right- and left-sided lesions were detected in 51.3% and 48.7% of patients, respectively. There were 55 (48.6%) patients who underwent MT (the MT group). In 42 (37.2%) patients, bridging IVT was used (group IVT + MT). IVT alone was applied in 16 (14.2%) patients (group IVT alone). In all groups, hemorrhagic transformation was observed in 25 (22.1%) patients. Malignant infarction and subarachnoid hemorrhage (SAH) developed in 11 (9.7%) patients. Only three patients had symptomatic intracranial hemorrhage (sICH). At the 24th hour, the median NIHSS score was 5. The distribution of the mRS scores on the 90th day revealed that 71 (62.8%) patients had good outcomes, whereas 22 (19.5%) patients died within 90 days after the intervention (Table 1).

Table 1.

Demographic and clinical characteristics of all patients.

	Overall (n = 113)
Age (years)	72.7 ± 15.1
Sex
Female	58 (51.3)
Male	55 (48.7)
Co-morbidities
Hypertension	85 (75.2)
Atrial fibrillation	43 (38.1)
Coronary artery disease	35 (31.0)
Diabetes mellitus	29 (25.7)
Cerebrovascular accident	16 (14.2)
Congestive heart failure	11 (9.7)
Hyperlipidemia	7 (6.2)
Peripheral artery disease	6 (5.3)
Admission time
The first hour	29 (25.7)
>270 min	35 (31.0)
mRS on admission
0	81 (71.7)
1	27 (23.9)
2	4 (3.5)
4	1 (0.9)
NIHSS at admission	11.0 (1.0–23.0)
Occluded side
Right	58 (51.3)
Left	55 (48.7)
MT	55 (48.6)
IVT + MT	42 (37.2)
IVT alone	16 (14.2)
Complications
Hemorrhagic transformation	25 (22.1)
HI1	13 (11.5)
HI2	4 (3.5)
PH1	8 (7)
Subarachnoid hemorrhage	11 (9.7)
Malignant infarction	11 (9.7)
Distal embolization	6 (6.5)
Symptomatic intracranial hemorrhage	3 (2.7)
NIHSS at 24th hour	5.0 (0.0–20.0)
mRS at 90th day
Excellent (mRS 0 and 1)	57 (50.4)
Good (mRS 0–2)	71 (62.8)
Mortality (mRS 6)	22 (19.5)

Values are given as n (%), mean ± SD, or median (range).

mRS, modified Rankin scale; NIHSS, National Institute of Health Stroke Scale.

The groups, according to the treatment modalities, were similar regarding the demographic characteristics of the patients (P > 0.05). A significant difference in the distribution of the admission time categories was detected between the groups (P < 0.001). Although the proportion of patients admitted within the first hour was similar among the groups, in the MT group, there were significantly more patients admitted after waiting longer than 270 min than in the other groups. The distribution of mRS scores at admission was significantly different between the groups (P = 0.009). The NIHSS score was significantly lower in the IVT group than in the MT (p = 0.001) and IVT + MT (P = 0.003) groups. A significant difference between the groups was detected in the NIHSS score at the 24th hour (P < 0.001). The NIHSS scores in the IVT group were significantly lower than those in the MT (P < 0.001) and IVT + MT (P = 0.002) groups. The other outcome parameters were similar between the groups (P > 0.05). The other clinical characteristics and 90th day mRS were similar between the groups (P > 0.05) (Table 2).

Table 2.

Comparison of groups based on the treatment modalities.

	MT (n = 55)	IVT + MT (n = 42)	IVT alone (n = 16)	P
Age (years)	77.0 (43.0–98.0)	75.5 (32.0–97.0)	73.0 (25.0–92.0)	0.470*
Sex
Female	31 (56.4)	19 (45.2)	8 (50.0)	0.551^†
Male	24 (43.6)	23 (54.8)	8 (50.0)
Co-morbidities
Hypertension	44 (80.0)	28 (66.7)	13 (81.2)	0.304^†
Atrial fibrillation	25 (45.5)	14 (33.3)	4 (25.0)	0.243^†
Coronary artery disease	20 (36.4)	10 (23.8)	5 (31.2)	0.406^†
Diabetes mellitus	15 (27.3)	8 (19.0)	6 (37.5)	0.327^†
Cerebrovascular accident	9 (16.4)	6 (14.3)	1 (6.2)	0.691^†
Congestive heart failure	7 (12.7)	3 (7.1)	1 (6.2)	0.682^†
Hyperlipidemia	1 (1.8) a	2 (4.8) a	4 (25.0) b	0.006 ^†
Peripheral artery disease	3 (5.5)	2 (4.8)	1 (6.2)	0.999^†
Admission time
The first hour	14 (25.5) a	12 (28.6) a	3 (18.8) a	<0.001 ^†
>270 min	34 (61.8) a	0 (0.0) b	0 (0.0) b
mRS on admission
0	36 (65.5) a	32 (76.2) a	13 (81.2) a	0.009 ^†
1	17 (30.9) a	10 (23.8) a	0 (0.0) b
2	2 (3.6) a. b	0 (0.0) b	2 (12.5) a
4	0 (0.0) a	0 (0.0) a	1 (6.2) a
NIHSS at admission	12.0 (6.0–22.0)	11.0 (6.0–23.0)	5.0 (1.0–18.0)	0.001 *
Occluded side
Right	32 (58.2)	18 (42.9)	8 (50.0)	0.324^†
Left	23 (41.8)	24 (57.1)	8 (50.0)
Superior M2	25 (46.3)	22 (61.1)	–	0.338^†
Inferior M2	15 (27.8)	6 (16.7)	–
Sup + Inf M2	14 (25.9)	8 (22.2)	–
Trifucation M2	1 (1.8)	1 (2.7)	–	0.999^†
Procedural complications
Hemorrhagic transformation	12 (21.8)	10 (23.8)	3 (18.8)	0.962^†
HI1	8 (14.5)	2 (4.7)	3 (100.0)	0.096^†
HI2	1 (1.8)	3 (7.1)	0 (0.0)
PH1	3 (5.4)	5 (11.9)	0 (0.0)
Subarachnoid hemorrhage	5 (9.1)	6 (14.3)	0 (0.0)	0.311^†
Malignant infarction	4 (7.3)	5 (11.9)	2 (12.5)	0.613^†
Distal embolization	3 (5.5)	3 (7.9)	–	0.699^†
Symptomatic intracranial hemorrhage	1 (1.8)	1 (2.4)	1 (6.2)	0.517^†
NIHSS at 24th hour	7.0 (0.0–20.0)	4.0 (0.0–17.0)	1.0 (0.0–6.0)	<0.001 *
mRS at 90th day
Excellent (mRS 0 and 1)	25 (45.5)	20 (47.6)	12 (75.0)	0.103
Good (mRS 0–2)	34 (61.8)	25 (59.5)	12 (75.0)	0.539
Mortality (mRS 6)	9 (16.4)	9 (21.4)	4 (25.0)	0.619

Values are given as n (%) or median (range).

Kruskal–Wallis H test.

†

Pearson’s chi-square or Fisher–Freeman Halton test.

a, b = letters in each row showing significant group differences.

IVT, patients with intravenous thrombolysis; IVT + MT, patients with intravenous thrombolysis with mechanical thrombectomy; mRS, modified Rankin scale; MT, patients with mechanical thrombectomy; NIHSS, National Institute of Health Stroke Scale.

A comparison of the procedural characteristics revealed no significant difference between the MT and IVT + MT groups (P > 0.005). The distribution of the final TICI recanalization results revealed that scores of 3 and 2c were detected in 59 (64.1%) and 20 (21.7%) patients, respectively. Four patients in the IVT + MT group were recanalized with IVT alone and underwent diagnostic angiography; no MT was performed (Table 3). In the IVT alone group, CTA was not performed to determine recanalization, and this group was not included in the recanalization results.

Table 3.

Comparison of the procedural characteristics in the MT and IVT-MT groups.

	MT (n = 55)	IVT + MT (n = 42)	P
Technical approach
ADAPT	1 (1.8)	4 (9.5)	0.607*
Stent retriever	48 (87.2)	30 (71.4)	0.297*
Combined approach	6 (10.9)	3 (7.1)	0.999*
First-pass effect	31 (56.4)	19 (54.3)	0.999*
Number of passes	1.0 (0.0–4.0)	1.0 (1.0–4.0)	0.944^†
Final TICI recanalization
0	6 (10.9)	2 (5.4)	0.896
2a	1 (1.8)	1 (2.7)
2b	2 (3.6)	1 (2.7)
2c + 3	46 (83.6)	33 (89.2)

Values are given as n (%) or median (range). Four patients were recanalized with TPA only DSA applied and arch could not be achieved in one patient.

Pearson’s chi-square, Fisher's exact, or Fisher–Freeman Halton test.

†

Kruskal–Wallis H test.

ADAPT, A Direct Aspiration first-Pass Technique for acute stroke thrombectomy; IVT + MT, patients with intravenous thrombolysis with mechanical thrombectomy; mRS, modified Rankin scale; MT, patients with mechanical thrombectomy; TICI, thrombolysis in cerebral infarction.

The demographic and clinical characteristics of the patients with superior and inferior divisions and both are given in Table 4. No significant differences were found between the clinical features of the patients with superior or inferior M2 lesions (P > 0.05). No significant difference was found in the procedural characteristics between the patient groups according to the location of the M2 lesions (P > 0.05). The groups were similar regarding the frequency of procedural complications (P > 0.05).

Table 4.

Outcomes of patients according to the M2 divisions.

	Localization			P
	Superior M2 only (n = 47)	Inferior M2 only (n = 21)	Superior M2 + inferior M2 (n = 22)	P
Age (years)	75.0 (32.0–90.0)	79.0 (47.0–98.0)	80.0 (43.0–97.0)	0.067^†
Sex
Female	28 (59.6)	12 (57.1)	8 (36.4)	0.182*
Male	19 (40.4)	9 (42.9)	14 (63.6)
Co-morbidities
Hypertension	34 (72.3)	14 (66.7)	18 (81.8)	0.519*
Atrial fibrillation	17 (36.2)	6 (28.6)	12 (54.5)	0.187*
Coronary artery disease	14 (29.8)	7 (33.3)	8 (36.4)	0.855*
Diabetes mellitus	11 (23.4)	6 (28.6)	5 (22.7)	0.880*
Cerebrovascular accident	7 (14.9)	3 (14.3)	4 (18.2)	0.935*
Congestive heart failure	4 (8.5)	3 (14.3)	2 (9.1)	0.820*
Hyperlipidemia	1 (2.1)	0 (0.0)	1 (4.5)	0.712*
Peripheral artery disease	2 (4.3)	1 (4.8)	2 (9.1)	0.839*
Admission time
The first hour	30 (63.8)	13 (61.9)	14 (63.6)	0.988*
>270 min	17 (36.2)	8 (38.1)	8 (36.4)
mRS on admission
0	36 (76.6)	11 (52.4)	15 (68.2)	0.232*
1	10 (21.3)	9 (42.9)	7 (31.8)
2	1 (2.1)	1 (4.8)	0 (0.0)
NIHSS at admission	11.0 (6.0–23.0)	10.0 (6.0–22.0)	12.0 (6.0–20.0)	0.196^†
Occluded side
Right	24 (51.1)	10 (47.6)	12 (54.5)	0.902*
Left	23 (48.9)	11 (52.4)	10 (45.5)
Technical approach
ADAPT	3 (6.3)	2 (9.5)	0 (0.0)	0.803*
Stent retriever	39 (82.9)	19 (90.5)	18 (100.0)	0.324*
Combined approach	5 (10.6)	0 (0.0)	4 (18.2)	0.123*
First-pass effect	24 (51)	13 (61.9)	12 (54.5)	0.802*
Number of passes	1.0 (1.0–4.0)	1.0 (1.0–3.0)	1.0 (0.0–4.0)	0.686^†
Final TICI recanalization
0	4 (8.5)	1 (4.8)	3 (13.6)	0.671*
2a	1 (2.1)	0 (0.0)	1 (4.5)
2b	3 (6.4)	0 (0.0)	0 (0.0)
2c + 3	39 (83.0)	20 (95.2)	18 (81.8)
Procedural complications
Hemorrhagic transformation	13 (27.7)	2 (9.5)	4 (18.2)	0.225*
Subarachnoid hemorrhage	3 (6.4)	4 (19.0)	4 (18.2)	0.202*
Malignant infarction	4 (8.5)	2 (9.5)	3 (13.6)	0.893*
Distal embolization	5 (10.6)	0 (0.0)	1 (4.5)	0.344*
Symptomatic intracranial hemorrhage	2 (4.3)	0 (0.0)	0 (0.0)	0.999*
NIHSS at 24th hour	5.0 (0.0–17.0)	7.0 (2.0–20.0)	8.0 (2.0–17.0)	0.165^†
mRS at 90th day
Excellent (mRS 0 and 1)	25 (53.2)	7 (33.3)	8 (36.4)	0.214*
Good (mRS 0–2)	30 (63.8)	12 (57.1)	11 (50.0)	0.544*
Mortality (mRS 6)	10 (21.3)	3 (14.3)	4 (18.2)	0.933*

Values are given as n (%) or median (range).

TICI: Thrombolysis in cerebral infarction NIHSS: National Institute of Health Stroke Scale, mRS: modified Rankin scale.

Pearson’s chi-square, Fisher's exact, or Fisher–Freeman Halton test.

†

Kruskal–Wallis H test.

ADAPT, A Direct Aspiration first-Pass Technique for acute stroke thrombectomy; mRS, modified Rankin scale; TICI, thrombolysis in cerebral infarction.

Discussion

No significant difference was found in the 90-day mRS score among the groups (MT vs. MT + IVT vs. IVT alone) in this series. While performing MT, the baseline NIHSS score is clearly important both for the indication and during the follow-up period. The current guidelines do not recommend MT for patients with low NIHSS scores (<6) (1,5). In our stroke center, all eligible patients receive IVT, but MT is not performed for exceptional clinical manifestations, such as aphasia and pure monoplegia, on patients with a low NIHSS score (<6). This explains why the NIHSS score was lower in the IVT alone group. A higher baseline NIHSS score (≥10) is an important independent factor for poor outcomes (6,11). The baseline and 24-h NIHSS scores were significantly greater in the MT and MT + IVT groups. A shorter last known normal (LKN) time is associated with a good prognosis (11). In our study, the LKN time was longer in the MT group because MT can be performed after 4.5 h, in contrast to tPA. Despite higher NIHSS scores and longer LKN times, sICH and 90-day mRS scores did not significantly differ (MT vs. MT + IVT vs. IVT alone).

Kniep et al. suggested that the administration of IVT to M2 occlusions decreases the risk for futile recanalization (12), but Cappellari et al. reported no significant improvement between the MT and IVT + MT groups (8). When comparing the MT and IVT + MT groups, the FPE and successful recanalization rates did not significantly differ in the present study. Our TICI 2c-3 recanalization rates are similar to those of previous series (13 –16). The TICI 2c-3 ratio (89.2%) was slightly greater in the IVT + MT group than in the control group, and in parallel hemorrhagic transformation, the SAH, malignant infarction, and sICH rates were also slightly greater in this group. The differences were not statistically significant. The hemorrhagic transformation and sICH rates in this study were similar to those in previous studies (2,9,11 –13,17). The incidence of SAH was 11%. In recent studies, the prevalence of SAH has been in the range of 24.7%–5.7% (7,14). A higher SAH rate might be associated with the ADAPT technique, but this difference was not statistically significant (7). The 90-day mRS score and mortality rates are in parallel with recent studies (8,11,13 –16). The good prognosis ratio was greater and the mortality ratio was lower in the MT group than in the IVT + MT group, but these differences did not reach statistical significance.

Several studies have compared aspiration methods versus SR methods for M2 occlusions (6,7,9,11,14 –19). Kim et al. claimed that SR thrombectomy may provide faster reperfusion (18). In studies comparing M1 and M2 occlusions, most M2 occlusions were treated with the SR technique (14,16). In contrast, Alawieh et al. concluded that the ADAPT technique is safe and effective for treating M2 strokes (9). Baharvahdat et al. and Toh et al. reported that the combined stent retrieval and aspiration technique was more effective (7,15). Finally, there are studies that have shown no significant difference between the two techniques (6,19). In our stroke center, SR techniques were preferred over the ADAPT technique because of the smaller diameter of the vessels and the increasing suction force. No significant differences were observed between the ADAPT, SR, or combined technique groups.

The laterality of the stroke and the anatomical division of the M2 segment might be predictive factors when performing MT. We did not detect a significant difference in the laterality of the stroke, similar to the findings of Bhogal et al. (14). Recent papers have suggested that a superior division of M2 is an independent predictor of more severe deficits, a longer procedural time, more thrombectomy attempts, and worse outcomes (3,9). In our study, the FPE and successful recanalization rates were slightly greater in the M2 inferior group than in the other groups, but these differences were not statistically significant. The 90-day outcome was similar in both groups.

The present study has some limitations. First, the study had a retrospective design. Second, selection bias cannot be ignored due to the lack of robust recommendations of guidelines supporting MT for patients with low NIHSS scores. Third, the eligibility criteria for IVT in MT patients are controversial. Finally, the relatively small number of patients, particularly in the ADAPT group, was the other drawback of the present study.

In conclusion, our data suggest that MT is safe and effective for stroke patients with M2 occlusions. Future prospective randomized trials based on the appropriate techniques for the anatomical divisions of the M2 segment are warranted.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Leyla Ramazanoglu

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