Abstract
Background and purpose
Recent randomized clinical trials have proved the efficacy of endovascular treatment of acute ischemic stroke in the anterior circulation. However, the benefit of endovascular treatment of ischemic stroke in the posterior circulation remains to be proven since it was excluded from these trials. We evaluate the benefit of endovascular treatment in posterior circulation strokes.
Methods
A total of 110 consecutive patients with posterior circulation stroke who underwent endovascular treatment in our institute in the period 1991–2015 were included. Recanalization rate according to modified Treatment in Cerebral Ischemia score and neurological outcome at three months according to modified Rankin Scale were the main outcomes. Collateral circulation, procedural complications and radiological outcome were evaluated in the radiological examinations.
Results
The median National Institutes of Health Stroke Scale was 31 (IQR: 13–31) and median time from symptom onset to groin puncture was 300 (IQR: 175–463) minutes. Successful recanalization was seen in 80 of 110 patients (73%). Favorable outcome (modified Rankin Scale ≤2) was seen in 38 patients (35%) while moderate favorable outcome (≤3) was seen in 48 patients (44%). Symptomatic intracerebral hemorrhage occurred in 10 patients (9%). An association between collateral circulation, recanalization rate and outcome was seen.
Conclusion
Endovascular treatment for posterior circulation stroke in this single-center cohort is relatively safe and effective with decreased mortality and increased favorable outcome compared to natural history.
Keywords: Angiography, posterior fossa, thrombectomy, thrombolysis, stroke
Introduction
Acute ischemic stroke (AIS) in the posterior cerebral circulation is associated with high mortality and morbidity if untreated or if recanalization does not occur.1 Recanalization is the best predictor of good outcome but the complex etiology and the multiple factors that have to be taken into account when choosing an appropriate treatment regimen make this stroke subtype very challenging to address.2
The treating physician has to consider if the occlusion is due to an embolus or a stenosis with in situ thrombosis, anatomical variations and the status of collateral circulation before choosing the appropriate treatment strategy. The various treatments that have been tried and are available are intravenous thrombolysis (IVT), intra-arterial thrombolysis (IAT), embolectomy either mechanical (ME) or by aspiration (AE), and stenting or angioplasty in case of stenosis. Unfortunately, IVT is associated with poor results in cases of large-vessel occlusion both in the anterior and posterior circulation. A number of randomized studies have shown that ME is associated with good recanalization rates and good neurological outcome in intracranial large-vessel occlusion of the anterior cerebral circulation.3 However, no randomized studies have evaluated the effectiveness of intra-arterial treatment in posterior circulation AIS.
In our institute, treatment of AIS in the posterior circulation has been performed since 1991 with the only available treatment at that time being IAT. ME became possible with the introduction of the GooseNeck snare in 1994 while stent retrievers were made available during the last decade.4,5 In this single-center, retrospective study, we evaluated the angiographic and neurological results of intra-arterial treatment of posterior circulation AIS. Furthermore, we applied a recently introduced radiological score, the Basilar Artery on Computed Tomography Angiography (BATMAN) score, to evaluate the collateral supply in the posterior circulation.6
Methods
The Sahlgrenska University Hospital serves both as a primary and secondary center for IVT and intra-arterial treatment of AIS. Patients who had undergone intra-arterial treatment for posterior AIS during the period 1991–2015 were identified in the prospective database of the Neurointerventional unit. Medical records and radiological data were reviewed. The study was approved by the Regional Ethical Review in Gothenburg.
A neurologist examined patients admitted to our hospital and neurological findings were scored according to the National Institutes of Health Stroke Scale (NIHSS).7 Deeply comatose patients were assigned a NIHSS score of 31. Overall responsiveness was assessed using the Reaction Level Scale-85 (RLS) (supplement).8 A non-contrast computed tomography (NCCT) or magnetic resonance imaging (MRI) examination of the head was then performed to exclude intracerebral hemorrhage and conditions mimicking AIS in the posterior circulation. The size of a possible demarcated infarct was not an absolute contraindication to intra-arterial therapy. After 2006 computed tomography angiography (CTA) or magnetic resonance angiography (MRA) of the head were also performed to identify the site of occlusion and evaluate collateral circulation and anatomical variants. According to the local protocol, the recommended time window for initiation of intra-arterial treatment in the posterior circulation was 12 hours from symptom onset. However, treatment was offered outside this time window after evaluation of the patient’s pre-stroke status, age, symptoms, radiological images and presumed prognosis. In patients with mild prodromal symptoms or fluctuating clinical status, the time of the last worsening was used as symptom onset time.
From 1991 to 2003, IVT was not the standard of care in our institute and IV infusion of heparin was used sometimes post-procedurally depending on the result of the endovascular treatment. In our institute, IVT became standard of care and was considered even for posterior circulation stroke after 2003. Patients eligible for intra-arterial treatment received an IV bolus dose of recombinant tissue plasminogen activator (rtPA) (0.9 mg/kg) and a continuous infusion of IV rtPA (maximum 90 mg) if presenting <3 hours after symptom onset (<4.5 hours after 2008) and no other contraindications to IVT existed. The “drip and ship” method was reserved for patients who were referred to us from other primary centers in the region of Västra Götaland. In those cases, IVT was started in the primary center and the patient was then directly transported to our institute. For IAT, urokinase was used until it was replaced by rtPA after 2003. In the beginning of the study period, only IAT was used, as no other methods were available. When the GooseNeck snare (Covidien, MA, USA) was introduced as an embolectomy device in 1994, the IAT still remained the most frequently used method in our department until the GooseNeck snare became the standard device for all operators in 2000. Over the years a number of other embolectomy devices such as the Solitaire FR Device (Medtronic, Minneapolis, MN, USA), the MERCI Retriever (Concentric Medical, CA, USA), the Embolus Retriever with Interlinked Cage (ERIC) Retrieval Device (Microvention Inc, Tustin, CA, USA) and the Penumbra 5MAX ACE system (Penumbra, CA, USA) were introduced in our institute but this was mostly at the end of the study period.
As a rule, intra-arterial AIS treatment in the posterior circulation was performed under general anesthesia. NCCT or MRI follow-up imaging was performed 22–36 hours after treatment.
Inclusion into this retrospective study required the following criteria to be met: presentation with a clinical picture of AIS due to an occlusion in a major artery in the posterior cerebral circulation, known time of symptom onset and that all radiological and clinical data were retrievable from the hospital archive.
The written report from the initial CT scan or MRI was reviewed for information on infarct size and location and, in case CTA or MRA were performed, also occlusion site and presence of collaterals. The periprocedural radiological images (CT, MRI and digital subtraction angiography (DSA)) were also re-evaluated by two trained neurointerventionists and neuroradiologists blinded to the written report, recanalization result and neurological status postoperatively and at three months. Functional status at three months after treatment was estimated by neurologists according to the modified Rankin Scale (mRS).
A study protocol was established in which we documented the time of stroke onset, symptoms, NIHSS and RLS at admission, use of intravenous rtPA, use of general anesthesia, extent of hypoattenuation in NCCT, location of occlusion in CTA and DSA, use of embolectomy device, recanalization score according to modified Treatment in Cerebral Ischemia (mTICI) (supplement), complications, functional status according to mRS at three months and all time intervals between stroke onset, NCCT examination, groin puncture, recanalization and procedure’s last image. In case of death within a three-month period, the cause was established.
To evaluate the extent of hypoattenuation in the NCCT the posterior circulation-Alberta Stroke Program Early CT score (pc-ASPECTS) and Pons-Midbrain Index (PMI) were applied to the pre- and post-procedural radiological examinations (supplement).9,10 For evaluation of the collateral circulation, the BATMAN score was used, which takes into account the thrombus burden and the collateral circulation (supplement). The cohort was divided and analyzed according to two outcome groups: good outcome, defined as mRS ≤ 2, or bad outcome, defined as mRS > 2, but also according to unsuccessful recanalization, defined as mTICI 0–2a and successful recanalization as mTICI 2b/3.
Statistical analysis
Non-Gaussian distributed data are presented as median and interquartile range (IQR) while normally distributed data are presented as mean and standard deviation. Accordingly, for differences in the outcome data between the groups, univariate analysis was performed using the Mann–Whitney U test or unpaired t test for continuous data and Fisher’s exact test for dichotomous data. Parameters with a probability value < 0.1 in the univariate analysis were included in the multiple logistic regression analysis of independent predictors of neurological outcome. Statistical significance was set to p < 0.05. Analysis was performed using IBM SPSS statistics, version 24.
Results
In total, 152 patients who underwent endovascular stroke treatment in the posterior circulation were identified in our database. Forty-two of these were excluded because of missing or low-quality data, unknown time of symptom onset or non-acute treatment of a posterior circulation occlusion. In all, 110 patients who met the inclusion criteria and their stroke characteristics are described in Table 1.
Table 1.
Stroke characteristics.
| All n = 110 | mRS ≤ 2 n = 38 | mRS > 2 n = 72 | p-value | |
|---|---|---|---|---|
| Age (mean ± SD) | 62 ± 13 | 58 ± 14 | 64 ± 12 | 0.023 |
| Males, no. (%) | 74 (67) | 26 (68) | 48 (66) | 0.853 |
| Hypertension, no. (%) | 52 (47) | 15 (39) | 37 (51) | 0.236 |
| Hyperlipidemia, no. (%) | 23 (21) | 11 (29) | 12 (17) | 0.134 |
| Diabetes mellitus, no. (%) | 9 (8) | 2 (5) | 7 (10) | 0.419 |
| Atrial fibrillation, no. (%) | 20 (18) | 6 (16) | 14 (19) | 0.638 |
| Antithrombotic, no. (%) | 20 (18) | 8 (21) | 12 (17) | 0.572 |
| Cause: | ||||
| Atherosclerosis, no. (%) | 38 (35) | 11 (29) | 27 (37,5) | 0.372 |
| Cardioembolic, no. (%) | 22 (22) | 9 (24) | 13 (18) | 0.485 |
| Dissection, no. (%) | 18 (16) | 6 (16) | 12 (17) | 0.906 |
| Unknown, no. (%) | 32 (28) | 12 (32) | 20 (28) | 0.678 |
| NIHSS (median IQR) | 31 (13-31) | 17,5 (6,75-31) | 31 (19-31) | 0.001 |
| NIHSS ≥ 25, No. (%) | 64 (59) | 16 (42) | 48 (67) | 0.011 |
| RLS (median IQR) | 4 (2-7) | 2 (1-6) | 6 (2-8) | 0.006 |
| Severity levels RLS 4-8, no. (%) | 57 (52) | 14 (37) | 43 (60) | 0.018 |
| Site of occlusion: | ||||
| Proximal basilar, no. (%) | 5 (5) | 1 (3) | 4 (6) | 0.502 |
| Middle basilar, no. (%) | 8 (8) | 4 (11) | 4 (6) | 0.342 |
| Distal basilar, no. (%) | 49 (44.5) | 23 (61) | 26 (36) | 0.039 |
| Whole basilar, no. (%) | 12 (11) | 0 (0) | 12 (17) | 0.008 |
| Mid-/distal basilar, no. (%) | 18 (16) | 5 (13) | 13 (18) | 0.511 |
| Proximal/mid-basilar, no. (%) | 12 (11) | 4 (11) | 8 (11) | 0.926 |
| Vertebral, no. (%) | 6 (5) | 1 (3) | 5 (7) | 0.346 |
| IV thrombolysis, no. (%) | 15 (14) | 6 (16) | 9 (12.5) | 0.418 |
| Time intervals, minimum (median IQR): | ||||
| Procedure | 99 (50–164) | 77 (38–128) | 111 (70–121) | 0.010 |
| Stroke onset-imaging | 106 (65–220) | 100 (57–166) | 164 (68–231) | 0.375 |
| Stroke onset-groin puncture | 300 (175–463) | 237 (159–494) | 315 (182–445) | 0.203 |
| Stroke onset-recanalization | 434 (271–584) | 387 (219–529) | 445 (295–612) | 0.071 |
IQR: interquartile range; IV: intravenous; mRS: modified Rankin Scale; NIHSS: National Institutes of Health Stroke scale; RLS: Reaction Level Scale.
Mean age of the whole cohort was 62 ± 13 and 67% were males. Median NIHSS was 31 (13–31) and median RLS was 4 (2–7). In 51 patients the NIHSS could not be assessed because they were in an unconscious state and an NIHSS score of 31 points was assigned. A significant association was seen between favorable outcome and younger age (p = 0.023), lower admission NIHSS (p = 0.001) and less severe RLS (p = 0.006). The site of occlusion was the distal basilar artery in the majority of the cases (above anterior inferior cerebellar artery level, 49 cases, 44.5%). Occlusion of the whole basilar artery was associated with unfavorable outcome (p = 0.008) while occlusion of the distal part of basilar artery was associated with favorable outcome (p = 0.039). Median time from stroke onset to imaging was 106 minutes (65–220) and from stroke onset to groin puncture was 300 minutes (175–463). Procedural time was significantly longer in patients with unfavorable outcome (p = 0.010).
Preprocedural imaging
NCCT of the head was the initial diagnostic method in the majority of the cases (101 cases, 92%) with MRI in the rest (nine cases, 8%). The median pc-ASPECTS score was 10 (8–10) and the median PMI was 0 (0–0) (Table 2).
Table 2.
Preprocedural imaging and procedural characteristics.
| All n = 110 | mRS ≤ 2 n = 38 | mRS > 2 n = 72 | p-value | |
|---|---|---|---|---|
| Preprocedural imaging: | ||||
| NCCT | ||||
| pc-ASPECTS, (median IQR) | 10 (8–10) | 10 (9–10) | 10 (8–10) | 0.146 |
| PMI, (median IQR) | 0 (0–0) | 0 (0–0) | 0 (0–0) | 0.430 |
| CTA | ||||
| BATMAN, (median IQR) | 7 (5.5–8) | 8 (7–8.5) | 7 (5–8) | 0.001 |
| CTA-SI pc-ASPECTS, (median IQR) | 7 (6–8) | 7.5 (6–8) | 7 (5–8) | 0.282 |
| CTA-SI PMI, (median IQR) | 2 (0–4) | 1 (0–2) | 2 (0–4) | 0.122 |
| Endovascular treatment: | ||||
| -IA thrombolysis, no. (%) | 17 (15) | 7 (18) | 10 (14) | 0.358 |
| -Embolectomy, no. (%) | 72 (65) | 25 (66) | 46 (64) | 0.507 |
| Aspiration, no. (%) | 18 (16) | 4 (11) | 14 (19) | |
| Mechanical, no. (%) | 54 (49) | 21 (55) | 33 (46) | |
| -Stenting/Angioplasty, no. (%) | 12 (11) | 4 (11) | 8 (11) | 0.600 |
| -No treatment, no. (%) | 9 (8) | 2 (5) | 7 (10) | 0.339 |
BATMAN: basilar artery on computed tomography angiography; CTA: computed tomography angiography; CTA-SI: CTA-source images; IA: intra-arterial; IQR: interquartile range; mRS: modified Rankin Scale; NCCT: non-contrast computed tomography; pc-ASPECTS: posterior circulation-Alberta Stroke Program Early CT score; PMI: Pons-Midbrain Index.
In 82 cases (75%), mainly those treated during the second half of the period (2006–2014), the diagnostic imaging protocol included a CTA in addition to the initial NCCT or MRA in case MRI was the radiological examination of choice. The median BATMAN score was 7 (5.5–8) and a low score was related to poor outcome (p = 0.001). On the other hand, no significant relationship was seen between pc-ASPECTS and PMI with neurological outcome.
Intra-arterial treatment
All patients were treated under general anesthesia except four patients (4%), who were treated under conscious sedation for medical reasons. One patient was converted to general anesthesia because of worsening and inability to maintain airway patency. Seventy-two patients (65%) were treated with embolectomy (54 cases ME and 18 cases AE). The second most frequent method was IAT used in 17 cases (15%). In 12 cases (11%) stent placement and angioplasty were the primary treatment method. Eight cases involved a significant stenosis in the basilar artery while four cases had a stenosis in the distal part of the vertebral artery. In nine cases (8%) the occlusion site could not be reached with a microcatheter or embolectomy device while in one of these cases spontaneous recanalization was observed in the initial angiograms (Table 2). Successful recanalization according to mTICI was defined as grades 2b/3 and was achieved in 80 cases (73%). Embolectomy (72 cases, 65%), primarily ME with the GooseNeck snare followed by AE, was the most frequent treatment method used and it was significantly associated with successful recanalization (p = 0.016) (Table 3).
Table 3.
Procedural characteristics and recanalization results.
| All n = 110 | mTICI 2b/3 n = 80, 73% | mTICI 0–2a n = 30, 27% | p-value | |
|---|---|---|---|---|
| -IA thrombolysis, no. (%) | 17 (15) | 12 (15) | 5 (17) | 0.519 |
| -Embolectomy, no. (%) | 72 (65) | 57 (71) | 15 (50) | 0.016 |
| Aspiration, no. (%) (Penumbra 5MAX ACE) | 18 (16) | 17 (21) | 1 (3) | |
| Mechanical, no. (%) | 54 (49) | 40 (50) | 14 (47) | |
| - GooseNeck snare, no. | 40 | 34 | 6 | |
| - Solitaire FR, no. | 11 | 5 | 6 | |
| -Merci Retriever, no. | 1 | 0 | 1 | |
| ERIC Retrieval Device, no. | 2 | 1 | 1 | |
| -Stenting/Angioplasty, no. (%) | 12 (11) | 10 (12.5) | 2 (7) | 0.310 |
| -No treatment, no. (%) | 9 (8) | 1 (1) | 8 (27) | <0.001 |
| Procedural complications: | ||||
| Dissection, no. (%) | 2 (2) | 0 (0) | 2 (7) | 0.073 |
| Perforation, no. (%) | 3 (3) | 0 (0) | 3 (10) | 0.019 |
| Migration, no. (%) | 12 (11) | 4 (5) | 8 (27) | 0.003 |
| mRS ≤ 2 at three months, no. (%) | 38 (35) | 35 (44) | 3 (10) | 0.001 |
| mRS ≤ 3 at three months, no. (%) | 48 (44) | 44 (55) | 4 (13) | <0.001 |
| Mortality at three months, no. (%) | 45 (41) | 24 (30) | 21 (70) | <0.001 |
ERIC: Embolus Retriever with Interlinked Cage; IA: intra-arterial; mRS: modified Rankin Scale; mTICI: modified Treatment in Cerebral Infarction.
Serious procedure-related complications in the form of dissection and perforation were seen in five cases (5%) and four of them were fatal. One of the two dissections observed occurred during guide-catheter placement requiring stent placement in the dominant vertebral artery. The patient survived with an mRS 5. The other dissection occurred during retrieval of the MERCI device in a basilar artery occlusion and it was fatal. Three cases of perforation were fatal. Two occurred while trying to place the microcatheter distally to occlusions in the basilar and in the cerebral posterior arteries, respectively. The third case was a perforation of the iliac artery that caused a severe retroperitoneal hematoma. The patient became hemodynamically unstable and underwent surgery but did not survive. Clot migration to arteries previously not affected by the initial occlusion was seen in 12 cases (11%). Six occurred during IAT while migration occurred using some type of embolectomy device in the other six cases (supplement). When recanalization was successful (mTICI 2b/3) 44% of the patients reached mRS ≤ 2 at three months and 55% reached mRS ≤ 3. With unsuccessful recanalization (grades 0–2a), the percentages of patients reaching a good outcome dropped to 10% mRS ≤ 2 and 13% mRS ≤ 3. Moreover, successful recanalization decreased the mortality rate to 30% from 70% in case of unsuccessful recanalization. In the binary logistical regression analysis the BATMAN score (odds ratio (OR) 1.73 (1.15–2.59)), p = 0.008 and successful recanalization (OR 10.92 (1.21–98.44)), p = 0.03 were independent predictors for good neurological outcome.
Radiological and neurological outcome
A post-procedural NCCT or MRI was available in 101 cases (92%), obtained at a median time of 20 hours and 58 minutes from the end of the DSA examination (IQR: 12 hours, 56 minutes–29 hours, 30 minutes). In nine cases no post-procedural follow-up was performed as the patients were declared dead (supplement). To define an intracerebral hemorrhage as symptomatic (sICH), deterioration in patient status post-procedurally should be documented. The deterioration was difficult to calculate as only 65 patients had an early post-procedural NIHSS and 57 patients were already unconscious before the procedure. At least 10 cases are thought to represent an sICH either because of a clear deterioration in the post-procedural clinical status by more than four NIHSS points or because of the extent of the ICH in the post-procedural imaging. All patients with sICH died except one, who survived with mRS 4 (Table 4).
Table 4.
Post-procedural and neurological outcome.
| All n = 110 | mRS ≤ 2 n = 38 | mRS > 2 n = 72 | p-value | |
|---|---|---|---|---|
| Recanalization: | ||||
| mTICI 2b/3, no. (%) | 80 (73) | 35 (92) | 45 (62.5) | 0.001 |
| Postprocedural imaging: | ||||
| pc-ASPECTS, (median IQR) | 6 (4–7) | 7 (5–9) | 6 (3–7) | 0.024 |
| PMI, (median IQR) | 2 (0–3) | 1 (0–2) | 3 (1–4) | 0.002 |
| NIHSS 24 (median IQR) | 11 (3–31) | 2 (0–4) | 31 (10–31) | <0.001 |
| sICH, no. (%) | 10 (9) | 0 (0) | 10 (14) | 0.011 |
| mRS ≤ 3 at three months, no. (%) | 48 (44) | |||
| Mortality at three months, no. (%) | 45 (41) | |||
| In-hospital mortality, no. (%) | 42 (38) | |||
| Cause of mortality, no. (%): | ||||
| Stroke | 36 (33) | |||
| Procedural complications | 4 (4) | |||
| Other | 5 (5) |
IQR: interquartile range; mTICI: modified Treatment in Cerebral Infarction; pc-ASPECTS: posterior circulation-Alberta Stroke Program Early CT score; PMI: Pons-Midbrain Index; NIHSS: National Institutes of Health Stroke scale; sICH: symptomatic intracerebral hemorrhage; mRS: modified Rankin Scale.
An mRS score at three months was available for all patients and a favorable outcome (mRS ≤ 2) was seen in 38 cases (35%) while a moderately favorable outcome (mRS ≤ 3) was seen in 44 cases (44%). The mortality rate (mRS = 6) at three months was 41% with in-hospital mortality 38% (supplement).
Discussion
Our study shows that a high recanalization rate and a favorable neurological outcome can be achieved with intra-arterial treatment in AIS compared to the natural history of posterior circulation AIS and the available data on IVT alone.11
A favorable outcome (mRS ≤ 2) was seen in 35% of the cases while a moderate favorable outcome (mRS ≤ 3) was seen in 44%. These results are as good as results seen in some of the randomized studies on endovascular treatment of anterior circulation AIS12 but are worse compared to other randomized studies that used more effective stroke workflow and strict patient selection criteria.13,14 Taking into account that the stroke workflow in our institute has improved dramatically over the years with dedicated stroke protocols and workflow schemes being introduced in the last decade of the study period, the less favorable outcome compared to studies with modern stroke protocols is not surprising. Overall, our results nevertheless imply a significant improvement compared to results of IVT alone or no treatment at all.1 Our results are also in line with those reported from the ENDOSTROKE registry (34% mRS ≤ 2 and 42% mRS ≤ 3) and better compared to the Basilar Artery International Cooperation Study (BASICS) registry (32% mRS ≤ 3).2,15 In our cohort and the ENDOSTROKE registry, embolectomy was the method of choice in the majority of cases while in the BASICS registry the number was less than half. Considering the recent evidence for the effectiveness of embolectomy in the anterior AIS, this alone may explain the better outcome in our study compared to the BASICS registry. Although IAT reached high recanalization rates (71%) in our cohort, it is associated with long infusion time, limited use because of contraindications to thrombolysis and high rate of embolus migration to other territories. ME and AE attained higher recanalization rate (79%) without contraindications and other disadvantages connected to IAT. Successful recanalization increased the proportion of patients with favorable outcome and inversely decreased the mortality in an otherwise devastating disease with reported mortality as high as 85%.
More than half of the patients (52%) were in an unconscious state (RLS ≥ 4) prior to initiation of the endovascular procedure, which was associated with poor outcome. The median NIHSS (31) was high compared to patients presenting with AIS in the anterior circulation and also higher than in other studies of the posterior circulation AIS, as in BASICS and ENDOSTROKE.2,15 The reason for the unusually high NIHSS level is that a score of 31 was assigned to all patients who were unconscious (RLS ≥ 4) and without prior NIHSS assessment. Unfortunately, the retrospective design of the study limits access to detailed neurological status of the patients before unconsciousness.
The selection of patients with posterior circulation AIS suitable for endovascular treatment is demanding because of the more complicated clinical picture compared to anterior AIS as well as the lower sensitivity of CT scans in the posterior intracranial fossa. Even computed tomography perfusion, which has been shown to improve patient selection in anterior AIS, has lower sensitivity in the posterior circulation, especially in detecting ischemic changes in the midbrain. MRI could possibly improve patient selection but lack of MRI-experienced radiologists and lack of MRI personnel during off hours limit its use in the acute setting. A number of radiological factors have been suggested to improve patient selection and prediction of outcome, such as pc-ASPECTS and PMI applied, both in NCCT and CTA source images.16,17 Recently, another radiological score, the BATMAN score, which combines the scoring of the collateral system in the posterior circulation as well as the clot burden, has been validated. We tested all these scores in our cohort but only the BATMAN score showed a significant correlation to outcome. The BATMAN score and successful recanalization were the only independent predictors of favorable neurological outcome in our cohort. The pc-ASPECTS and PMI showed no correlation to neurological outcome, thus making patient selection on the basis of the extent of hypoattenuation in the pre-procedural CT unreliable.
A major limitation of our study is its retrospective nature and that direct comparison of the different treatment modalities was not possible. Moreover, the stroke logistics in the early years differs from the more organized stroke workflow today, with delays in patient arrival and transportation within and between hospitals being much more common in the past. Advanced radiological methods were not available until late in the study period, and patients in the early years were examined only with plain CT scans of lower quality. Lastly, long-term follow-ups to evaluate patency and symptom recurrence are missing in patients who received a permanent stent.
Our study is one of the largest single-center case series on AIS in the posterior cerebral circulation, including not only the experience of the early era of intra-arterial treatment but also more modern approaches in treatment of large intracranial vessel occlusion. It contributes to the better understanding and better management of posterior circulation AIS while awaiting evidence from large randomized trials.18,19
Conclusion
Intra-arterial treatment of posterior circulation AIS, primarily with embolectomy, is a relatively safe and effective method, reaching high recanalization rates that can improve neurological outcome and decrease mortality rate. The newly validated BATMAN score was the only preprocedural radiological score shown to be an independent predictor of favorable neurological outcome.
Supplemental Material
Supplemental material for Endovascular treatment of acute ischemic stroke in the posterior circulation by Alexandros Rentzos, Jan-Erik Karlsson, Christer Lundqvist, Lars Rosengren, Mikael Hellström and Gunnar Wikholm in Interventional Neuroradiology
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 disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Swedish State Support for Clinical Research grant number [ALFGBG-590861]. The funder had no involvement in the study design, data collection, analysis and interpretation, writing or decision to submit the paper.
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Supplementary Materials
Supplemental material for Endovascular treatment of acute ischemic stroke in the posterior circulation by Alexandros Rentzos, Jan-Erik Karlsson, Christer Lundqvist, Lars Rosengren, Mikael Hellström and Gunnar Wikholm in Interventional Neuroradiology