Computed Tomography Perfusion Deficit as an Indicator for Reperfusion in Large-vessel Occlusions with Low National Institutes of Health Stroke Scale Scores in Acute Ischaemic Stroke: A Retrospective Review

Abstract

Background: Endovascular thrombectomy (EVT) has proven to be successful in acute ischaemic stroke (AIS) with a National Institutes of Health Stroke Scale (NIHSS) score of >8, but remains controversial in AIS with an NIHSS score of <8. This study evaluated computed tomography (CT) perfusion indicators for EVT in large-vessel occlusion (LVO) ischaemic strokes with low NIHSS scores. Methods: We retrospectively reviewed data from 49 patients with AIS, LVO and an NIHSS score of <8 who received medical therapy (n=27), or rescue (n=10) or urgent (n=12) thrombectomy. Therapy decision was made from clinical course and perfusion imaging. The urgent group underwent EVT in <6 hours. The rescue group underwent EVT in >6 hours due to increasing NIHSS scores; this included patients who presented after 6 hours and underwent urgent EVT. Modified Rankin scores were obtained at 3 months to assess outcomes. Results: More patients in the urgent group (91.7%) had a discharge NIHSS improvement (>1) compared with the rescue (50.0%) and medical (51.9%) groups (p=0.02). The urgent group displayed thrombolysis in cerebral infarction (TICI) scores of 2b/3 in 100% of patients, whereas the rescue group displayed TICI scores of 2b/3 in 80% and 1/2a in 20% (p=0.076). The perfusion core (cerebral blood flow [CBF] <30%) was not different between the groups (2.1 cm3, 1.0 cm3 and 9.2 cm3, for urgent, rescue and medical groups, respectively). The perfusion penumbra (time to max [Tmax] >6 s) and mismatch (Tmax minus CBF) were significantly larger for the urgent and rescue groups. Penumbra volume was 80.1 cm3, 107.5 cm3 versus 50.6 cm3 (p=0.011), and mismatch was 78.0 cm3, 106.5 cm3 versus 41.5 cm3 (p=0.002) for urgent and rescue thrombectomy versus medical therapy, respectively. Conclusion: The biggest driver of urgent reperfusion was a larger penumbra seen on CT perfusion, which appeared to show better outcomes in NIHSS scores at discharge without any difference in 3-month outcomes graded by modified Rankin scores. Our data suggest that larger perfusion deficits on CT imaging may serve as a tool for patient selection for EVT in LVO with an NIHSS score of <8 and should be investigated further.