LAUSR

In Response: We thank Brinjikji et al for their interest in our study. We agree that the use of the acronym ASPECTS (Alberta Stroke Program Early CT Score) without further specification may be misinterpreted on a first glimpse, and we want to highlight that it was not our intention to mislead the reader. However, ASPECTS is currently also used when evaluating infarct cores based on DWI-sequences, but we agree that a specification such as DWI-ASPECTS (diffusion weighted imaging ASPECTS) should be used to avoid misunderstandings. To address this issue, the repercussions and limitations of including both DWIASPECTS and ASPECTS by computed tomography (CT) scan are extensively discussed in our article. The poor correlation between DWI-ASPECTS and ASPECTS by CT scan is indeed not easy to overcome and data helping to correct for this modality inherent bias—specifically in low ASPECTS cases—are sparse. The data you put forward—albeit relying on a very small sample—specifically questions if DWI-ASPECTS 4 and 5 is a reliable surrogate for ASPECTS ≤5 by CT scan. However, when comparing median volumes of infarct cores across strata of DWI-ASPECTS and ASPECTS by CT scan, these were found to be ≈60 cc, ≈110 cc, ≈125 cc, ≈175 c, ≈180 cc, and ≈275 cc for DWI-ASPECTS 5, 4, 3, 2, 1 and 0 and ≈25 cc (corrected 50 cc) and ≈35 cc (corrected 70 cc) for ASPECTS by CT scan 5 and 4. Correction was based on findings derived by a correlation of magnetic resonance imaging–DWI volume and core volume estimations using relative cerebral blood flow <30% on CT perfusion imaging (see Figure II in the online-only Data Supplement). Specifically, DWI-ASPECTS <4 seems to be a decent surrogate of large infarct core volumes, that is, >100 cc. When restricting our analysis to DWI-ASPECTS 0 to 3 and ASPECTS by CT scan 0 to 5 (n=132), likely to represent patients with either a large infarct core or true ASPECTS 0 to 5 patients, the rates of modified Rankin Scale score 0 to 2, symptomatic intracranial hemorrhage, and mortality were 16.7%, 9.8%, and 50%, respectively. The odds ratios regarding a beneficial effect of successful reperfusion on these outcome parameters were comparable to those reported in the full cohort (adjusted odds ratio, 2.51; 95% CI, 0.57–11.04; adjusted odds ratio, 0.26; 95% CI, 0.06–1.14; adjusted odds ratio, 0.29; 95% CI, 0.11–0.82 for modified Rankin Scale score 0–2, symptomatic intracranial hemorrhage, and mortality). The correlation of DWI-ASPECTS and ASPECTS by CT scan with associated infarct core volumes needs further investigations and will most likely depend on several factors, for example, time from symptom-onset to imaging or how the respective raters have handled small embolic infarctions within the DWI-ASPECTS cohort. As you mention, the outcome discrepancy of patients with either DWI-ASPECTS 0 to 5 or ASPECTS 0 to 5 by CT scan is probably partially explained by differences in true infarct core size inherent to the intermodality difference. However, one also has to keep in mind that some centers of the BEYONDSWIFT registry (The Bernese-European Registry for Ischemic Stroke Patients Treated Outside Current Guidelines With Neurothrombectomy Devices Using the SOLITAIRETM FR With the Intention for Thrombectomy) have access to both magnetic resonance imaging and CT for patient selection, and there may be a bias that preferentially unstable, intubated, more agitated patients were imaged by CT in these centers. This may have contributed to the poor outcome of low ASPECTS by CT scan in addition to intermodality associated differences in infarct core volumes on admission. Indeed, patients with ASPECTS 0 to 5 selected by CT had substantially higher National Institutes of Health Stroke Scale, as did patients with DWI-ASPECTS 0 to 5 (median 18 versus median 12; P=0.004). Interestingly, the outcome of patients with ASPECTS by CT scan 0 to 5 compares lower (modified Rankin Scale score 0–2; 10%) than what has been observed in other cohorts with ASPECTS 0 to 5 by CT scan (17.9%, N=21/117, not all treated by mechanical thrombectomy, but up to 42.8% modified Rankin Scale score 0–2 in successfully reperfused patients), which may be explained by this bias. Certainly, our study alone is not a proof that endovascular therapy is safe in all patients with ASPECTS 0 to 5 by CT scan without doubt. However, the presented observations corroborate recently published data. This is true for rates of symptomatic intracranial hemorrhage and also for a potential beneficial effect of successful reperfusion on clinical outcome. Most importantly, the results illustrate that a low ASPECTS score per se is not a single and robust parameter to withhold endovascular treatment as advocated in the past. Nevertheless, careful treatment decisions are warranted, especially in light of the high risk of death or severe dependency irrespective of reperfusion status. Considering the above-mentioned points, the analyses provided may rather be regarded as a piece of the puzzle in the complex interpretation of observational data available on endovascular treatment in patients with large infarct cores. We want to thank Brinjikji et al for their critical dissection of the data and analyses, which helps to clarify potential misinterpretation of the data and stresses the need for further research on that topic.