Characteristics of acute occlusion of the intracranial vertebral artery and endovascular treatment

Abstract

To investigate the characteristics of acute occlusion of the intracranial vertebral artery (IVA) and endovascular treatment. Patients with acute IVA occlusion treated with endovascular thrombectomy were prospectively enrolled, and the clinical, treatment and 90-d data were analyzed. Forty-two patients were enrolled, with an age range 34–82 (57 ± 12) years, including 38 (90.48%) male and 4 (9.52%) female patients. Twenty-one (50.0%) patients underwent stent thrombectomy as the preferred recanalization technique, and 36 (85.7%) multiple modes of recanalization. Among the techniques used, balloon angioplasty was performed in 35 (83.3%) patients, stent implantation in 33 (78.6%), stent thrombectomy in 27 (64.3%), and thrombus aspiration in 6 (14.3%). The time from onset to first recanalization of blood vessels was 127–1517 [median 593.5 (326.3, 736.3)] minutes, and the time from puncture to first recanalization was 39–243 [median 67.0 (50.5, 81.3)] minutes. Successful recanalization with the mTICI grade 2b and 3 was present in 40 (95.2%) patients, including mTICI grade 3 in 25 (59.5%) and 2b in 15 (35.7%). Fifteen (35.7%) patients experienced periprocedural complications, including intraprocedural thrombus escape and embolism in 11 (26.2%) patients and symptomatic intracranial hemorrhage in 4 (9.5%). During 90-d follow-up, 16 (38.1%) patients obtained functional independence, 19 (45.2%) achieved good prognosis, and all-cause mortality was present in 9 (21.4%). Compared with patients with good prognosis, those with poor prognosis had significantly (P < 0.05) higher NIHSS scores but lower posterior communicating artery opening rate. Acute IVA occlusion is characterized by intracranial atherosclerosis and progressive stroke and can be successfully recanalized. High baseline NIHSS score and low posterior communicating artery opening rate may be related to poor prognosis.

Introduction

Strokes in the posterior circulation take up about 20% of all ischemic strokes, and acute occlusion of the vertebrobasilar artery account for 5% of large vessel occlusive strokes^{1, 2, 3, 4–5}. Compared with large-vessel occlusion in the anterior circulation, the rate of large vessel occlusion in the posterior circulation is lower, with non-specific clinical symptoms, fluctuating conditions, difficult diagnosis, and lower rates of recanalization and good prognosis of endovascular treatment for acute occlusion of posterior circulation arteries^6,7. The mortality rate of conservative treatment for acute occlusion of large blood vessels and vertebrobasilar arteries in the posterior circulation is as high as 40%, and nearly 80% have poor prognosis⁸. Endovascular treatment (EVT) for such patients is a hot research topic. However, specialized studies on acute occlusion of the intracranial segment of the vertebral artery are rare, and the imaging features and EVT strategies have not been explored. This study was performed to investigate the characteristics of acute occlusion of the intracranial vertebral artery (IVA) and endovascular treatment strategies.

Materials and methods

This prospective single-center study was approved by the ethics committee of Henan Provincial People’s Hospital, and all patients or their family members had signed the informed consent to participate. All methods were conducted in accordance to the relevant guidelines and regulations. Patients with acute IVA occlusion were prospectively enrolled to undergo EVT between February 2017 and March 2022. The inclusion criteria were patients aged 18–85 years with acute IVA occlusion confirmed by digital subtraction angiography (DSA), time from disease onset to femoral artery puncture for treatment within 24 h, modified thrombolysis in cerebral infarction (mTICI) grade < 1, modified Rankin Scale (mRS) score ≤ 2 ⁹, the National Institutes of Health Stroke Scale (NIHSS) score ≥ 8 ¹⁰, and pretreatment posterior circulation Albert Stroke Program early computed tomography score (pc-ASPECTS) ≥ 3 ¹¹. The exclusion criteria were patients with large vessel occlusion in both posterior and anterior circulations, severe dysfunction of important organs like liver and kidney, and history of stent implantation in the vertebral basilar artery.

The diagnosis of acute IVA occlusion was mainly based on the characteristics of the disease and imaging examinations, characterized by sudden neurological deficits, severe symptoms, and rapid progression, such as sudden contralateral hemiplegia, hemiparesis, ataxia, hoarseness, choking on water, acute IVA occlusion, and acute cerebral infarction of the corresponding blood supply area. The etiology of acute IVA occlusion was divided into the intracranial atherosclerotic disease, cardiogenic embolism, and arterial dissection. For intracranial atherosclerotic diseases, the patients usually had hypertension, diabetes mellitus, hyperlipidemia, and smoking, with the onset type being progressive. After successful recanalization of the atherosclerotic blood vessel, residual stenosis ≥ 50% was usually present at the original occluded site, or significant distal hypoperfusion caused by residual stenosis. For cardiogenic embolism, the symptom onset was sudden and reached the peak immediately, with no obvious focal residual stenosis after mechanical thrombectomy. For arterial dissection, acute IVA occlusion was secondary to fusiform or irregular aneurysmal dilation of IVA, or had imaging evidence of intramural hematoma, intimal flap, or double lumen. The disease onset types were divided into the acute, progressive, and remission-aggravated type.

The following data were collected: patients’ age, sex, risk factors (hypertension, diabetes mellitus, coronary atherosclerotic heart disease, atrial fibrillation, past history of stroke, and smoking), onset type (acute: the neurological deficit reached its peak after onset, progressive: the neurological deficit showed stepwise or progressive aggravation after onset, and remission-aggravated: the neurological deficit improved and then worsened after the onset of the disease), NIHSS score, pc-ASPECTS, the basilar artery on computed tomography angiography (BATMAN) score to evaluate the collateral compensation¹² the pons midbrain index (PMI) to assess the infarction severity of the pons and midbrain¹³ mTICI score, recanalization strategies (stent thrombectomy, thrombus aspiration, stent angioplasty, balloon angioplasty, or multiple modes including some of the above approaches), number of passes of mechanical thrombectomy, and time from onset to recanalization or from femoral puncture to recanalization. When the mTICI was ≥ 2, it was defined as successful recanalization, and when the mTICI was 3, it was defined as complete recanalization¹⁴. All evaluations were independently performed by two senior neurointerventional physicians with 8 years of clinical experience, and consensus was reached through negotiation in case of disagreement.

Thrombolysis bridging therapy was performed using the tissue type plasminogen activator for patients with the disease onset within 4.5 h and no contraindications to thrombolysis. For patients with contraindications to thrombolysis, endovascular thrombectomy was conducted directly. All patients underwent general anesthesia for endovascular thrombectomy. The preferred approach was the femoral artery approach, and if the route was tortuous and difficult to send in endovascular devices, the radial artery approach was used. After inserting an arterial sheath, intravenous injection of unfractionated heparin (50U/kg) was administered via bullet injection before cerebral angiography to assess arterial occlusion and collateral circulation. Mechanical thrombectomy was performed using stent retrievers or contact suction devices inside a 6 F guiding catheter which was placed within the IVA proximal to the occluded location. If the thrombectomy device could not be successfully passed through the occluded segment, balloon dilatation was conducted. For balloon dilatation, an SL-10 Excelsior microcatheter (Stryker, Fremont, CA, USA) was carefully navigated across the occlusion location with the guidance of a 200-cm 0.014-inch (0.036 cm) ASAHI guide wire (Asahi, Nagoya, Aichi, Japan) before a 300-cm ASAHI micro-guide wire was exchanged into the IVA distal to the occlusion. Then, a Gateway balloon catheter with the balloon diameter of 80% normal vascular diameter (2.0 mm× 15 mm–2.5 mm × 15 mm, Stryker, Fremont, CA, USA) was selected for dilatation of the occluded or stenotic location. When stent placement or balloon dilation was used as the initial opening technique, it was called direct angioplasty; when the blood flow state could not be maintained after mechanical thrombectomy and further balloon dilation or stent placement is required, it was called remedial angioplasty. For patients with persistent severe stenosis (stenosis degree ≥ 70%) after 3 passes, resulting in insufficient distal perfusion or high risk of reocclusion for successful reperfusion, remedial treatment such as balloon dilation and/or stent placement was considered. All patients underwent immediate postoperative flat CT examination to screen for complications of intracranial hemorrhage. For patients undergoing stent implantation in the emergency department, antiplatelet aggregation agents were routinely used postoperatively, with intravenous administration of tirofiban hydrochloride at a dose of 10 µ g/kg, followed by a micro-pump infusion of 0.1 µ g/kg/min, maintained for at least 12 h postoperatively. Head CT plain scan was performed from 24 to 48 h postoperatively to evaluate cerebral infarction, intracranial edema degree, and intracranial hemorrhage.

After the procedure, perioperative complications were evaluated, including intraoperative thrombus escape, intraoperative arterial dissection, symptomatic intracranial hemorrhage within 7 days after surgery¹⁵. Symptomatic intracranial hemorrhage was defined as new intracranial hemorrhage demonstrated on cerebral imaging associated with any of the following item¹⁵: ≥4 NIHSS points at diagnosis compared to immediately before worsening, ≥ 2 points in one NIHSS category, intubation/hemicraniectomy/external ventricular drain placement or other major medical/surgical intervention, and absence of alternative explanation for deterioration. The mRS score at 90 days after endovascular thrombectomy was assessed, with mRS ≤ 2 defined as functional independence, mRS score ≤ 3 as good prognosis, and mRS score > 3 as poor prognosis¹⁶. According to the postoperative 90-d mRS score, patients were divided into a good (mRS ≤ 3) prognosis group and a poor (mRS > 3) prognosis group. The main clinical outcomes were the 90-d functional independence rate and 90-d good prognosis rate. The secondary clinical outcomes were 90-d postoperative mortality rate and perioperative complication rate.

Statistical analysis

The SPSS 25.0 software (IBM, Chicago, IL, USA) was used for statistical analysis of this study. For continuous measurement data in the normal distribution (confirmed by the Shapiro Wilk method) were presented as mean and standard deviation and tested with the student t test or as median and interquartile range and tested with the Mann-Whitney U test. Counting data were presented as number and percentage and tested with the Chi square test or Fisher exact probability test. The significant P value was set at < 0.05.

Results

Forty-two patients were enrolled, with an age range 34–82 (57 ± 12) years (Table 1), including 38 (90.48%) male and 4 (9.52%) female patients. Hypertension was present in 34 (81.0%) patients, smoking in 18 (42.9%), past stroke in 18 (42.9%), diabetes mellitus in 12 (28.6%), coronary atherosclerotic heart disease in 9 (21.4%), and atrial fibrillation in 2 (4.8%). The progressive onset type was present in 24 (57.1%) patients, acute in 12 (28.6%), and remission-aggravated in 6 (14.3%). Intracranial atherosclerotic disease was present in 40 (95.2%) and arterial dissection in 2 (4.8%).

Table 1. Baseline data.

Variables		Total (42)	Good prognosis (19)	Poor prognosis (23)	P
Age (y)		57 ± 12	58 ± 13	56 ± 10	0.71
Male sex (n,%)		38(92.9%)	16 (84.2)	20 (87.0%)	0.47
Risk factors	Hypertension	34 (81.0%)	15 (78.9%)	19 (82.6%)	0.98
	Smoking	18(42.9%)	7 (36.8%)	11 (47.8%)	0.47
	Past history of stroke	18(42.9%)	6 (31.6%)	12 (52.2%)	0.18
	Diabetes mellitus	12(28.6%)	4 (21.1%)	8 (34.8%)	0.33
	CAHD	9(21.4%)	5 (26.3%)	4 (17.4%)	0.75
	Atrial fibrillation	2(4.8%)	1 (5.3%)	1 (4.3%)	0.98
Onset type	Progressive	24(57.1%)	9 (47.4%)	15 (65.2%)	0.48
	Acute	12(28.6%)	7 (36.8%)	5 (21.7%)
	Remission-aggravated	6(14.3%)	3 (15.8%)	3 (13.0%)
Etiology	ICAD	40(95.2%)	17 (89.5%)	23 (100%)	0.20
	Arterial dissection	2(4.8%)	2 (10.5%)	0

CAHD coronary atherosclerotic heart disease, ICAD intracranial atherosclerotic disease.

The baseline NIHSS score was 8–35 (median 20 (11.8, 28.0)), pc-ASPECTS 3–9 (median 8.0 (6,0, 8.0)), PMI 0–4 (median 0.0 (0.0, 2.0)), BATMAN 3–10 (median 6.5(5.0, 8.0)) (Table 2). The ischemic cerebral infarction was located in cerebellum in 34 (81.0%) patients, pons in 16 (38.1%), occipital lobe in 10 (23.8%), thalamus in 7 (16.7%), medulla oblongata in 4 (9.5%), and midbrain in 3 (7.1%). On DSA imaging, the acute occlusion was distal to the posterior inferior cerebellar artery in 23 (54.8%) patients and proximal to the posterior inferior cerebellar artery in 15 (35.7%), whereas in four (9.5%) patients, the posterior inferior cerebellar artery was absent. The proportion of contralateral vertebral artery being slender (i.e. the affected vertebral artery being the dominant vertebral artery) was the highest (73.8%, 31/42), with normal blood vessels only in 4 cases (9.5%), arterial stenosis in 2 (4.8%) and occlusion in 5 (11.9%). In 22 (52.4%) patients, the posterior communicating artery was open.

Table 2. Clinical, imaging and treatment data.

Variables		Total (42)	Good prognosis(19)	Poor prognosis (23)	P
Scores (median, Q1-Q3)	NIHSS score	20.0(11.8,28.0)	16.0 (11.0, 23.0)	23.0(15.0, 30.0)	0.03
	Pc-ASPECTS	8.0(6.0,8.0)	8.0(6.0, 8.0)	8.0(6.0,8.0)	0.94
	PMI	0.0(0.0,2.0)	0.0(0.0,2.0)	0.0(0.0,2.0)	0.88
	BATMAN	6.5(5.0,8.0)	7.0(5.0, 8.0)	6.0(5.0,8.0)	0.58
Acute infarction locations (n,%)	Cerebellum	34(81.0)	16 (84.2)	18 (78.3)	0.93
	Pons	16(38.1)	7 (36.8)	9 (39.1)	0.88
	Occipital lobe	10(23.8)	4 (21.1)	6 (26.1)	0.98
	Thalamus	7(16.7)	3 (15.8)	4 (17.4)	0.98
	Medulla oblongata	4(9.5)	1 (5.3)	3 (13.0)	0.74
	Midbrain	3(7.1)	1 (5.3)	2 (8.7)	0.99
Occlusion features (n,%)	Proximal to the posterior inferior cerebellar artery	15(35.7)	9 (47.4)	6 (26.1)	0.15
	Slender, stenotic or occluded contralateral vertebral artery	38 (90.5)	18 (94.7)	20 87.0)	0.74
	Opened Pcom	22(52.4)	14 (73.7)	8 (34.8)	0.01
Recanalizing techniques (n,%)	Balloon dilatation	35(83.3)	16 (84.2)	19(82.6)	0.98
	Stent angioplasty	33(78.6)	15 (78.9)	18(78.3)	0.99
	Stent retriever	27(64.3)	10 (52.6)	17(73.9)	0.15
	Thrombus aspiration	6(14.3)	3 (15.8)	3(13.0)	0.98
Angioplasty (n,%)	Direct angioplasty	16(38.1)	7(36.8)	9(39.1)	0.88
	Remedial angioplasty	25(59.5)	11 (57.9)	14(60.9)	0.85
No. of mechanical thrombectomy (median, Q1-Q3)		1.0(0.0,2.0)	1.0(0.0,1.0)	1.0(0.0,2.0)	0.37
Time (median, Q1-Q3), min	From onset to recanalization	593.5(326.3,736.3)	504.0(310.0,737.0)	601.0(341.0,896.0)	0.74
	From puncture to recanalization	67.0(50.5,81.3)	76.0(55.0,93.0)	63.0(45.5,72.0)	0.07
Successful reperfusion (n,%)		40(95.2)	19 (100)	21(91.3)	0.49
Periprocedural complications (n,%)		15(35.7)	5 (26.3)	10(43.5)	0.25

NIHSS the National Institutes of Health Stroke Scale, pc-ASPECTS posterior circulation Albert Stroke Program early computed tomography score; PMI, the pons midbrain index, BATMAN the basilar artery on computed tomography angiography, Pcom posterior communicating artery.

Among the 42 patients, 10 (23.8%) underwent bridging therapy. Thirty-nine (92.9%) underwent right femoral artery puncture approach, and 3 (7.1%) experienced right femoral artery puncture firstly but later changed to right radial artery approach due to tortuous path. The time from onset to first recanalization of blood vessels was 127–1517 [median 593.5 (326.3, 736.3)] minutes, and the time from puncture to first recanalization of blood vessel was 39–243 [median 67.0 (50.5, 81.3)] minutes (Table 2).

Twenty-one (50.0%) patients underwent stent thrombectomy as the first recanalization technique, and 36 (85.7%) multiple modes of recanalization (Tables 2 and 3). Among the techniques used, balloon angioplasty was performed in 35 (83.3%) patients, stent implantation in 33 (78.6%), stent thrombectomy in 27 (64.3%), and thrombus aspiration in 6 (14.3%). Direct stent angioplasty was performed in 16 (38.1%) patients and remedial stent angioplasty in 25 (59.5%). For mechanical thrombectomy, 21 (50.0%) patients were recanalized with only thrombectomy once. Thirty-seven stents were deployed in 33 (78.6%) patients, with two stents deployed at the vertebral artery ostium and 35 stents in the IVA (20 self-expanding and 15 balloon-expanding stents). Successful recanalization with the mTICI grade 2b and 3 was present in 40 (95.2%) patients, including mTICI grade 3 in 25 (59.5%) and 2b in 15 (35.7%).

Table 3. Endovascular treatment of patients with AIVAO.

Variables		Data (n,%)
Preferred recanalization technique	Stent retriever	21 (50.0%)
	Balloon dilatation	16 (38.1%)
	Thrombus aspiration	5 (11.9%)
Multi-modes of recanalization		36(85.7%)
Techniques of recanalization	Balloon dilatation	35(83.3%)
	Stent angioplasty	33(78.6%)
	Stent retriever	27(64.3%)
	Thrombus aspiration	6(14.3%)
Angioplasty	Direct angioplasty	16(38.1%)
	Remedial angioplasty	25(59.5%)
Number of mechanical thrombectomy	0	11(26.2%)
	1	21(50.0%)
	2	6(14.3%)
	3	4(9.5%)
Type of stents deployed	Self-expanding	18(42.9%)
	Balloon-expanding	13(31.0%)
	Both	2(4.8%)
Successful reperfusion	mTICI 3	25(59.5%)
	mTICI 2b	15(35.7%)

AIVAO acute intracranial vertebral artery occlusion, mTICI modified thrombolysis in cerebral infarction.

Fifteen (35.7%) patients experienced periprocedural complications (Table 2), including intraprocedural thrombus escape and embolism in 11 (26.2%) patients [with only thrombus escape in 6 (14.3%) patients, combined arterial dissection in 3 (7.1%), and combined sICH in 2 (4.8%) within 7 days] and sICH only in 4 (9.5%) within 7 days. The total rate of sICH was 14.3% (6 patients). The endovascular recanalization was failed in two (4.8%) patients because of intraprocedural arterial dissection which prevented the passage of micro-guide wire across the occluded segment with the mTICI grade 0. In one patient, arterial dissection occurred during aspiration of a thrombus escaped to the upper basilar artery after balloon dilatation of the occluded IVA. Both patients without successful recanalization died during follow-up.

During 90-d follow-up, 16 (38.1%) patients obtained functional independence, 19 (45.2%) achieved good prognosis, and all-cause mortality was present in 9 (21.4%). No significant (P > 0.05) differences were found in the baseline data between patients with good and poor prognosis (Table 2). Compared with patients with good prognosis, those with poor prognosis had significantly (P < 0.05) higher NIHSS scores but lower posterior communicating artery opening rate (Table 2).

Discussion

After investigating the characteristics of acute IVA occlusion and EVT, it was found that acute IVA occlusion was characterized by intracranial atherosclerosis and progressive stroke and could be successfully recanalized. High baseline NIHSS score and low posterior communicating artery opening rate may be related to poor prognosis.

So far, there have been few independent research reports on acute IVA occlusion undergoing EVT, as previous studies have mostly included acute IVA occlusion in the category of acute basilar artery occlusion or directly excluded acute IVA occlusion cases. Our study systematically analyzed the clinical characteristics, EVT strategies, and prognosis of acute IVA occlusion within 24 h of onset in a single center. It was found that patients with acute IVA occlusion have the following characteristics: more than 90% are male, the proportion of intracranial atherosclerotic disease is extremely high, and the contralateral vertebral artery is often slender, with the occluded side being mostly the dominant vertebral artery. Hypertension is the most common risk factor, with progressive stroke in most patients and acute infarction most commonly in cerebellar infarction. Most (85.7%) of the acute IVA occlusions required application of multimodal recanalization techniques, with balloon dilation and stent implantation being the most commonly used, resulting in a high success rate of reperfusion (95.2%), a high incidence of thrombus escape (26.2%), a 90-d good prognosis rate 45.2% and a 90-d mortality rate 21.4%.

Exploring the clinical imaging features of acute IVA occlusion is helpful for clinical decision-making as it is an important source of blood supply for the posterior circulation. In this study, acute IVA occlusion was mostly in males, individuals with a history of hypertension, and smokers, all of whom are risk factors for intracranial atherosclerotic disease¹⁷. According to the New England Medical Center’s posterior circulation registration study, IVA is the site with the highest rate of posterior circulation atherosclerotic disease¹⁸. In our study, over 90% of patients with acute IVA occlusion were found to have intracranial atherosclerotic diseases in the vertebral artery, and the contralateral vertebral artery was thin, narrow, or occluded. This can easily cause hemodynamic instability in the posterior circulation, reduced blood flow, decreased reserve capacity, and thrombus clearance rate, leading to the formation of acute thrombosis. Therefore, caution should be exercised in screening and primary prevention of acute IVA occlusion against risk factors for intracranial atherosclerotic disease. Our study also found that 42.9% of patients with acute IVA occlusion had a history of stroke, and 57.1% had a progressive disease course. Therefore, for these patients, timely identification and prevention of disease progression are necessary.

The male proportion in our study was significantly higher than the female proportion, and the specific reason for this is currently unclear. Smoking is one risk factor for intracranial atherosclerosis¹⁷ and may be one reason for the higher male proportion because most females in China do not smoke. The specific duration of patient enrollment, single-center study design, and a small cohort of patients may also be the reason for the proportional imbalance of sex in the prevalence of acute IVA occlusion.

Regarding the recanalization technique, 50.0% of patients in our study were treated with stent thrombectomy as the initial preferred thrombectomy technique. Mechanical thrombectomy before angioplasty can effectively reduce the thrombus burden in the occluded segment and quickly restore blood flow. Compared with the direct angioplasty rate (38.1%), the overall remedial angioplasty rate in our study was still high (59.5%), which was related to acute IVA thrombosis on the basis of intracranial atherosclerotic stenosis. Direct stent angioplasty was not used as much as other techniques in order to reduce the proportion of foreign bodies (stents) placed inside the body. Moreover, simple stent thrombectomy cannot directly repair local stenosis, and the thrombectomy device may damage the intima of the vessel and even induce plaque to rupture or fall off when passing through the narrowed vessel, leading to reocclusion of the vessel and application of rescuing angioplasty¹⁹. In our study, self-expanding stents were used more commonly than balloon-expanding ones (42.9% vs. 31.0%), which is because the self-expanding stent has better trafficability and lower risks of complications caused by perforating artery occlusion than the balloon-expanding stents²⁰.

In our study, stent implantation was performed in 33 (78.6%) patients. It is a safer technique to perform only balloon dilatation in the acute phase and stenting in the subacute phase when antiplatelet therapy has been sufficiently effective^{21, 22, 23, 24, 25, 26–27}. Nonetheless, in case of poor compliance of the patients with antiplatelet medication, thrombosis may occur and cause reocclusion of the IVA and subsequently severe consequences. Moreover, if dual antiplatelet therapy was administrated sufficiently effectively, stent implantation would not cause thrombosis and severe consequences. Stent implantation following balloon dilatation performed in one session of endovascular treatment will thus be more efficient and convenient^{21, 22, 23, 24, 25, 26–27}. This is why the number of cases of stenting in the acute phase in our study was very high. Nevertheless, percutaneous transluminal angioplasty (PTA) and stenting in the acute phase of ischemic stroke may result in significantly higher rates of thrombotic complications than in the non-acute phase because of the hypercoagulation status associated with acute ischemic stroke^28,29 and damage from balloon angioplasty and stents deployed as a foreign-body may both increase thrombosis.

High reperfusion rates, good prognosis, and lower mortality rates have been reported for endovascular mechanical thrombectomy. In a systematic review investigating the outcomes and complications of mechanical thrombectomy for acute posterior circulation occlusions³⁰, good prognosis at 3 months follow-up was achieved in 38% patients (16-75%), a mortality rate in 30% (4-64%), and successful reperfusion in 86% (62-100%). Two recent randomized controlled trials confirmed that mechanical thrombectomy of the posterior circulation was superior to medication therapy, with the success rate of mechanical reperfusion 88-93%, good prognosis rate at 90 days after surgery 46%, and mortality rate at 90 days 31-37%^31,32. In patients treated with best medical care^31,32, the good prognosis rate at 90 days was 23% and 24%, and the mortality rate was 55% and 42% within 90 days, respectively. In one study assessing endovascular treatment for acute basilar artery occlusion via a Nationwide Prospective Registry³³, the good prognosis at 90 days was 9.3% vs. 32.0% and the mortality rate was 71.4% vs. 46.2% for the standard medical treatment vs. mechanical thrombectomy. In contrast, our study had a higher success rate of reperfusion (95.2%), a lower mortality rate (21.4%), and a good prognosis rate (45.2%), which may be due to the fact that our study only included patients with acute IVA occlusion and excluded complex cases such as those with serial occlusion and basilar artery occlusion. The overall incidence of perioperative complications in our study was 35.7%. Two cases of failed opening were forced to terminate the surgery due to intraoperative complications. It can be seen that perioperative complications will increase the difficulty of opening, delay reperfusion time, and lead to poor prognosis. Although there was no statistically significant difference in the incidence of perioperative complications between the good and poor prognosis groups in our study (P > 0.05), the incidence of perioperative complications in the poor prognosis group still showed an increasing trend. Therefore, reducing the occurrence of complications such as thrombus escape during intravascular opening may be the key to restoring perfusion as soon as possible and improving the prognosis with acute IVA occlusion.

In the comparative analysis of patients with different prognoses, it was found that the baseline NIHSS score was higher and the proportion of posterior communicating artery opening was lower in the poor prognosis group in our study. This result suggested that patients with high baseline NIHSS scores have more severe neurological deficits. Previous studies have shown that baseline NIHSS scores are not only closely related to larger infarct volumes³⁴ but also can accurately predict the postoperative 90 day prognosis³⁵. Poor opening of the posterior communicating artery may not be conducive to the formation of good collateral circulation, and poor collateral circulation is significantly correlated with the mortality rate of acute IVA occlusion¹⁹. Therefore, in clinical diagnosis and treatment, it is important to pay attention to the evaluation of the degree of posterior communicating artery opening.

Currently, no specific studies of endovascular treatment of acute IVA occlusion have been performed, and cases of acute ICA occlusion may be included in studies of posterior circulation occlusion. The periprocedrual complications of endovascular treatment of acute ICA occlusion may be compared with those of endovascular treatment of acute basilar artery occlusion because of the location similarity of the basilar artery right above the IVA. In our study, periprocedural complications occurred in 15 (35.7%) patients, including thrombus escape in 6 (14.3%), combined thrombus escape and arterial dissection in 3 (7.1%), combined thrombus escape and sICH in 2 (4.8%) within 7 days, and sICH only in 4 (9.5%) within 7 days, with a total sICH of 14.3% (6 patients). In one clinical trial of acute thrombectomy of basilar artery occlusion³² periprocedural complications consisted of sICH in 12 (5.3%) patients, non-symptomatic ICH in 19 (8.4%), and other complications in 32 (14.2%) patients including 6 (2.7%) arterial dissections and 5 (2.2%) vascular perforations, with a total complication rate of 27.9% (63/226). In the ATTENTION randomized trial of endovascular treatment for acute basilar-artery occlusion³⁶ sICH occurred in 12 (5.3% or 12/226) patients and non-symptomatic ICH in 31 (13.7% or 31/226), with a total ICH rate of 14.6% (33/226). In one study assessing endovascular treatment for acute basilar artery occlusion³³ periprocedural complications included sICH in 45 of 636 patients (7.1%), arterial perforation in 7 (1.1% or 7/647), arterial dissection in 10 (1.5% or 10/647), distal embolization in 27 (4.2% or 27/647), and cerebral vasospasm in 18 (2.8% or 18/647), with a total complication rate of 16.7%. The total complication rate and sICH rate were not the same in these studies because of different choice criteria of patients and time of endovascular treatment. The complication rate in our study is also different from those of other studies because of the location of acute occlusion, treatment time and methods, and anatomical differences between the IVA and basilar artery.

Some limitations existed in this study, including the one-center study design, a small sample of patients, Chinese patients enrolled only, no randomization, no control of medication, and no long-term follow-up. Moreover, our center is an advanced stroke center, with most patients being transferred from lower-level hospitals, resulting in severe conditions and higher risks of EVT. All these issues may affect the outcomes and generalization of the study. Future prospective, randomized, controlled, multicenter studies will have to be performed with multiple races and ethnicities enrolled for better outcomes.

In conclusion, acute IVA occlusion is characterized by intracranial atherosclerosis and progressive stroke and can be successfully recanalized with multiple modes of treatment. But the complication rate caused by thrombus escape is high, and high baseline NIHSS score and low posterior communicating artery opening rate may be related to poor prognosis.

Author contributions

Study design: Liang-Fu Zhu, Tian-Xiao Li; Data collection: Yun-Peng Li, Zhi-Long Zhou, Yang Zhang, Li-Na Wang, Li-Heng Wu, Liang-Fu Zhu; Data analysis: Yun-Peng Li, Zhi-Long Zhou, Yang Zhang, Li-Na Wang, Li-Heng Wu, Liang-Fu Zhu; Writing of the original version: Zhi-Long Zhou, Yang Zhang; Revision: Bu-Lang Gao; Guarantor: Liang-Fu Zhu; Review and approval: All authors.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.

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