Clinically Relevant Findings on 24-hour Head CT after Acute Stroke Therapy: the 24-hour CT Score

Background: Routine head computed tomography (CT) is performed 24 hours post-acute stroke thrombolysis and thrombectomy, even in patients with stable or improving clinical deficits. Predicting CT results that impact management could help prioritize patients at risk and potentially reduce unnecessary imaging. Methods: In this IRB-approved retrospective study, data from 1461 consecutive acute ischemic stroke patients at our Comprehensive Stroke Center (n=8943, 2012-2022) who received intravenous thrombolysis or endovascular therapy, exhibited stable or improving 24-hour exams, and underwent 24-hour follow-up head CT per standard acute stroke care guidelines. CT reports 24 hours post-stroke were reviewed for edema, mass effect, herniation, and hemorrhage. The primary outcome was any clinically relevant 24-hour CT finding that led to changes in antithrombotic treatment or blood pressure goals, extended ICU stays or hospitalizations, neurosurgical interventions, or administration of mannitol or hypertonic saline. Multivariable logistic regression identified independent predictors of clinically meaningful CT abnormalities. A 24-hour CT Score was developed and cross-validated. Results: The mean age was 70 years, with 47% women. The median NIH Stroke Scale (NIHSS) score at admission was 12 (IQR 6-18). Stroke-related abnormalities on 24-hour CT were present in 325 patients (22.2%), with 183 (12.5%) showing clinically relevant findings. Age, admission NIHSS, and blood glucose levels were independent predictors of clinically relevant 24-hour CT findings. The final model C statistic was 0.72 (95% CI, 0.68-0.76) in the derivation cohort and 0.72 (95% CI, 0.67-0.75) in bootstrapping validation. The 24-hour CT score was developed using these predictors: NIHSS score 5-15 (+3); NIHSS score ≥16 (+5); age <75 years (+1); admission glucose ≥140mg/dL (+1). The prevalence of clinically relevant CT findings was 4.3% in the low-risk group (24-hour CT score ≤4), 11.3% in the medium-risk group (score 5), and 21.4% in the high-risk group (score ≥6). The 24-hour CT score demonstrated good calibration. Conclusion: In patients undergoing thrombolysis or thrombectomy who undergo routine 24-hour head CT despite remaining clinically stable or improving, only 1 in 8 prove to have 24-hour head CT findings that impact management. The 24-hour CT score provides risk stratification that may improve resource utilization.