Kevin S. Attenhofer, MD
@KAttenhofer
Today, we are seeing a more and more expanded role of endovascular therapy (EVT) in acute ischemic stroke. Despite the ever-growing body of research describing indications for EVT, we continually see patients in practice who do not “fit the mold” of the various trials’ inclusion criteria. Weighing heavily on many stroke practitioners is how to best approach and manage the patient with an apparent large vessel occlusion with a mild corresponding clinical syndrome. How can we predict if these patients will incur more benefit or risk from EVT? While some clinical trials are pending, this observational study describes a prediction score based on age and stroke severity which they called the Stroke Checkerboard (SC) score.
The SC score consists of a graded scale ranging from 2 to 15. This was calculated by adding 1 point for each decade from 50 to 90 years of age and 2 points for every increase of 5 points on the National Institutes of Health Stroke Scale (NIHSS). The weights of age and NIHSS in the SC score were derived from logistic regression using good outcome (modified Rankin Scale (mRS) 0–2) as the dependent variable in a derivation cohort of 1119 patients from one hospital. Receiver operating characteristic curves were performed to identify 2 thresholds that would define a low CS score group with a positive predictive value, >0.80 for good outcome, an intermediate CS score group, and a high CS score group with positive predictive value >0.80 for poor outcome (mRS 4–6). The SC score was validated in 2088 other patients from 4 independent cohorts.
Figure 1. The stroke checkerboard score. One point is added per decade from 50 to 90 years of age, and 2 points are added per stratum of 5 points on the National Institutes of Health Stroke Scale (NIHSS). A score inferior to 8 defines low scores (black), a score of 8 to 12 defines intermediate scores (gray), and a score superior to 12 defines high scores (light gray).
Applying this score to their patients, the authors conducted a multicenter observational study of over 4000 patients hospitalized between 2006 and 2015 in the Paris region. 358 patients were treated with EVT only, 514 received EVT and tPA, and 1845 patients received tPA only, and 1362 were treated with neither. The primary outcome used to assess treatment effects on functional outcome was the adjusted common odds ratio (OR) for a shift in the direction of an improvement in the mRS. They found that EVT was associated with a better outcome in patients with SC score > 8. Conversely, in patients with SC score < 8, EVT was associated with poorer outcomes than controls. Their findings were statistically significant.
Figure 2. Scores on the modified Rankin Scale at 90 days in the overall population. Distribution of scores at 90 days in the intervention and control groups in the overall population of the Paris Stroke Consortium registry, for patients with stroke checkerboard (SC) scores <8, with SC scores 8 to 12, or with SC scores >12. Shift analysis showed a benefit of endovascular treatment only in patients with SC score >12 (P=0.011) and SC score 8 to 12 (P=0.003) but a significant harm in patients with SC score <8 (P=0.012). The interaction was significant at P<0.001.
The authors also conducted a case-control analysis in which they selected 449 patients with LVO in the anterior circulation treated with EVT and 449 patients with LVO in the anterior circulation not treated with EVT. In this subgroup, EVT was again associated in shift analyses with better outcome in patients with high (adjusted OR, 3.02; 95% CI, 1.75–5.20) and intermediate SC scores (OR, 1.92; 95% CI, 1.39–2.63) and was associated with no benefit in patients with low SC scores (OR, 0.87; 95% CI, 0.52–1.45).
While randomized controlled data would be most helpful, the score described in this paper is a simple bedside tool which may help practitioners determine the best treatment strategy for younger patients with LVO and a low NIHSS, while also reinforcing the need to intervene on older, sicker patients.
