Cerebral perfusion studies (CPS) can enhance the benefits of mechanical thrombectomy (MT) beyond the standard 6-hour post-stroke window, although favourable functional outcomes remain achievable in a substantial proportion of patients selected based on clinical judgement alone without CPS. These findings, from a study by researchers at the University of Hong Kong (HKU), suggest that stroke patients should not be routinely denied treatment solely because of delayed presentation or lack of CPS availability.
The retrospective cohort study included 480 patients who underwent MT between January 2019 and January 2025 at Queen Mary Hospital. Primary outcomes were 3-month modified Rankin Scale (mRS), door-to-groin puncture time, recanalization rate, procedural complications and mortality. Secondary outcomes included differences in 3-month functional status between patients who underwent MT with or without prior CPS. [Hong Kong Med J 2026;32:200-207]
Among the 51/480 patients who underwent extended-window MT (at ≥6 hours from either symptom onset or last-known-well time to groin puncture), 72.5 percent (n=37; median age, 75 years; male, 56.8 percent) had anterior circulation stroke, and 27.5 percent (n=14; median age, 68; male, 64.3 percent) had posterior circulation stroke. The median onset-to-groin puncture time among these extended-window patients was 8 hours after symptom onset. The overall complication rate was 7.8 percent.
At 3 months, 16/37 (43.2 percent) of patients with anterior circulation stroke and 1/14 (7.1 percent) of patients with posterior circulation stroke achieved functional independence (mRS ≤2). The functional recovery rate of patients with anterior circulation stroke was comparable to the 46 percent rate found in HERMES, a meta-analysis of five landmark trials, four of which included patients who underwent MT within 6 hours. [Lancet 2016;387:1723-1731]
CPS were performed to guide selection in 15 patients (40.5 percent) with anterior circulation stroke. Use of CPS depended on service availability rather than predefined selection criteria. Despite a longer door-to-puncture time (167 vs 89.5 minutes; p<0.001) in patients who underwent CPS, CPS use was associated with a significantly higher rate of functional independence at 3 months compared with patient selection based on clinical judgement alone (66.7 vs 27.3 percent; p=0.018), suggesting that CPS enhanced patient selection for extended-window MT.
“The lack of CPS availability, [however], should not preclude extended-window MT, given that our overall outcomes were comparable to those of clinical trials using CPS-based selection criteria for extended-window treatment,” wrote the authors. [N Engl J Med 2018;378:708-718; N Engl J Med 2018;378:11-21]
“The study findings provide evidence supporting clinical service development to facilitate CPS adoption and extended-window MT in Hong Kong,” concluded the authors. “Additionally, capacity building and the development of standardized clinical pathways are urgently required to ensure that patients receive appropriate treatment at the right place and at the right time.”