Cereda CW, Bianco G et al. Perfusion Imaging Predicts Favorable Outcomes after Basilar Artery Thrombectomy. ANN NEUROL 2022;91:23–32
Randomized trials support the use of perfusion imaging to identify patients with anterior circulation large vessel occlusive disease that are likely to benefit from thrombectomy. There is paucity of data on the use of perfusion imaging as well as demonstrating a benefit of thrombectomy in basilar artery occlusion (BAO). The authors of the current study sought to investigate the utility of perfusion imaging to identify BAO patients that may benefit from endovascular therapy.
This multi-center retrospective cohort study, performed in 11 centers, included patients aged ≥ 18 years, with BAO on CT or MR angiography and NIHSS >2 treated within 36 hours, who received CT or MR perfusion imaging prior to thrombectomy. A Critical Area Perfusion Score (CAPS), based on Tmax > 10 sec, was prespecified to quantify critical posterior circulation brain regions affected by severe hypoperfusion. The following regions were scored: cerebellum (1 point per hemisphere), pons (2 points), midbrain and/or thalamus (2 points) for a total of 6 possible points. Patients were dichotomized into favorable CAPS (≤3) and unfavorable CAPS (>3). The threshold were set after a prior pilot study ROC analysis that determined poor functional outcome at 90 days with 100% specificity. The primary hypothesis was that patients with fewer regions of severe hypoperfusion (or CAPS ≤3), would have a more favorable response to endovascular treatment.
103 patients were dichotomized into CAPS ≤3 (90 [87%]) and CAPS >3 (13 [13%]). There was good interrater agreement in CAPS scoring. Patients with a CAPS ≤3 had a lower median presentation NIHSS (12.5, IQR 7-22 Vs. 23, IQR 19-36; p=0.010). Successful reperfusion (mTICI 2b-3) rates were achieved in 84%, without differences between the groups. When reperfusion was achieved, 64% of CAPS ≤3 patients had a favorable outcome (mRS ≤3) compared to 8% of non reperfused CAPS ≤3 patients (OR = 21, 95% CI 2.6-170, p <0001). None of the CAPS >3 patients had a favorable outcome regardless of mechanical reperfusion. In reperfused patients, CAPS >3 predicted poor outcome with specificity of 100% and sensitivity of 26%. CAPS ≤3 was an independent predictor of favorable outcome after adjustment in multivariate regression analysis (OR 39.25, 95% CI 1.34 - >999, p=0.033). Baseline core infarct volume and PC-ASPECTS scores were not predictors of outcome. In the analysis of secondary outcomes, reperfused patients with CAPS ≤3 were more likely to be independent (mRS 0-2), had lower rates of death or severe disability and a shift toward favorable outcomes in mRS ordinal shift analysis (cOR 7.8, p<0.001). Both CAPS and reperfusion were associated with an mRS shift among all patients. None of the CAPS >3 patients were functionally independent.
The key finding of this study is that cerebral perfusion imaging identifies basilar artery occlusion patients that are likely to benefit from reperfusion. Patients with a CAPS ≤3 had very favorable outcomes, whereas CAPS > 3 patients did poorly regardless of reperfusion status. The authors suggest that the ‘absence of severe hypoperfusion within key structures in posterior fossa (CAPS ≤3) may accurately identify patients with a small ischemic core prior to thrombectomy’. Limitations of this study include the small sample size, particularly CAPS >3 group (n=13), a retrospective study design, and varied perfusion protocols that utilized both CT and MR. Furthermore it is unclear if the CAPS score has been externally validated and the futility of endovascular therapy in patients with CAPS>3 will require larger studies. This trial does identify a subset of population with BAO that may skew posterior circulation thrombectomy trials towards a negative outcome. Future trials may consider eliminating this subset from the eligibility criteria.
Sanjeev Sivakumar MD
Assistant Professor Neurocritical Care
University of South Carolina Greenville School of Medicine