Patients
Between January 2011 and December 2020, a total of 128 consecutive patients with acute BAO received endovascular thrombectomy at a comprehensive stroke center. Of these, 5 patients without pretreatment diffusion-weighted imaging (DWI), 6 patients without posttreatment DWI, and one patient without 90-day modified Rankin Scale (mRS) data were excluded from the study. Clinical and radiologic data of the remaining 116 patients were retrieved from a prospectively collected database and analyzed. The institutional review board approved this study and waived the requirement to obtain informed consent on the basis of the retrospective study design.
Endovascular Therapy
Inclusion criteria for endovascular thrombectomy were as follows: occlusion of the basilar artery confirmed on catheter angiography, presentation within 12 hours of stroke onset or last seen normal, baseline National Institutes of Health Stroke Scale (NIHSS) score ≥ 4, and no intracranial hemorrhage on pretreatment computed tomography (CT). Intravenous thrombolysis with recombinant tissue plasminogen activator was performed in eligible patients before thrombectomy. Endovascular procedures were performed under local anesthesia in most patients. Conscious sedation was used at the discretion of the neurointerventionalists. Endovascular thrombectomy was performed with either a stent retriever or a large-bore aspiration catheter as a first-line device. Balloon angioplasty with or without stent placement was performed to treat underlying severe (≥70%) atherosclerotic stenosis, if needed. We did not perform additional recanalization procedures for SCA occlusion even if it was revealed on final angiograms.
Imaging Analysis
All patients included in the study underwent pretreatment DWI and follow-up DWI within 3 days after the endovascular procedure. DWI examination were performed with a 1.5T system (Signa HDxt; GE Medical Systems, Milwaukee, Wisconsin, USA) or a 3.0T system (Ingenia 3.0T CX, Philips Medical Systems, Best, Netherlands). At DWI, the SCA territory infarction was defined as diffusion-restricted lesions in the upper half of the ipsilateral cerebellar hemisphere or middle cerebellar peduncle or in the lateral or posterior region of the midbrain [10,11]. The presence or absence and types of SCA infarction (cerebellar or midbrain) were recorded in each patient. We also assessed the posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) on pretreatment DWI.
The patency or occlusion of the superior cerebellar arteries was assessed on final angiograms. The site of BAO was classified as proximal, middle, or distal on initial angiograms in accord with previous studies [12]. Overall reperfusion status was assessed on final angiograms according to the modified Thrombolysis in Cerebral Infarction (mTICI) score. Successful reperfusion was defined as an mTICI score of 2b or 3. All patients with SCA occlusion underwent follow-up brain CT angiography before discharge. CT angiography source images, thick-slab maximum-intensity projection images in axial, coronal, and oblique coronal plains, and volume-rendering images were reviewed to evaluate the patency of SCAs. At CT angiography, we defined the late spontaneous recanalization as clear visualization of the ostium and whole arterial segments of previously occluded SCA. Post-treatment CT scans were evaluated to identify intracranial hemorrhages according to the Heidelberg bleeding classification.13 Symptomatic cerebellar hemorrhage was defined, according to the Heidelberg classification, as any cerebellar hemorrhage associated with clinical evidence of neurological worsening, with the hemorrhage judged to be the principal cause of neurologic decline [13]. Malignant cerebellar infarction was defined as a cerebellar infarction causing mass effect in the posterior cranial fossa resulting in decompressive craniectomy or in-hospital mortality [14]. All imaging examinations including DWI, angiography, CT, and CT angiography were retrospectively assessed by two neuroradiologists who were blinded to clinical information. Conclusions were made by consensus in case of disagreement between two readers.
Clinical outcomes
Clinical outcomes were assessed by stroke neurologists using a modified Rankin scale (mRS) score during an outpatient visit or by telephone interviews at 90 days after endovascular therapy. A favorable outcome was defined as an mRS score of 0 to 3. We also assessed the length of hospital stay and occurrence of malignant cerebellar infarction and in-hospital mortality. Patients with in-hospital mortality were excluded from the analysis of the length of hospital stay.
Statistical analysis
Continuous variables are presented as the median and interquartile range. Categorical variables are presented as the number and percentage. The χ2 test or Fisher exact test was used for categorical variables, and the Mann-Whitney U test was used to compare continuous variables. We compared baseline characteristics, procedural factors, malignant cerebellar infarction, in-hospital mortality, length of hospital stay, and 90-day mRS between patients with SCA occlusion and without it. Statistical analyses were performed using SPSS software (Version 26.0; IBM SPSS, Chicago, IL). A P value <.05 was considered significant. Logistic regression analysis was performed to identify independent predictors of 90-day favorable outcome. The logistic regression analysis included variables that showed a P value of <.05 in univariate analysis.