Patients with mild acute ischemic stroke who had Tmax + 6-second volumes of 15 mL or greater were more likely to have poor functional outcomes at 90 days, according to a multicenter registry analysis.
In the retrospective study of 655 patients presenting within 24 hours of symptom onset across centers in Australia and Indonesia, 314 patients had National Institutes of Health Stroke Scale (NIHSS) scores of 5 or less. Among this subgroup, 22.9% (n = 72) demonstrated hypoperfusion defined as a Tmax + 6-second volume of 15 mL or greater, indicating substantial tissue at risk.
Investigators stated that the patients with mild stroke and Tmax + 6-second volumes of 15 mL or greater had poorer outcomes at 90 days compared with those below this threshold. Functional dependence, defined as modified Rankin Scale (mRS) scores of 3 to 6, occurred in about 26% vs 10%, respectively. Median mRS scores were 1 vs 0, respectively.
The investigators analyzed multimodal imaging, including noncontrast computed tomography (CT), CT angiography, and CT perfusion processed using RAPID software. Tissue at risk was defined using a prespecified perfusion threshold, and large vessel occlusion was identified on angiography involving major intracranial arteries.
Large-vessel occlusion was present in 11.5% (n = 36/314) of the patients with mild stroke compared with 37.2% (n = 127/341) of those with moderate or higher stroke. Predictors of significant hypoperfusion in this group included atrial fibrillation, higher baseline stroke severity, and large-vessel occlusion, with occlusions in the middle cerebral artery M1 segment and internal carotid artery showing particularly strong associations.
Multivariable analysis identified perfusion lesion volume of 15 mL or greater, hypertension, and large-vessel occlusion as independent predictors of poor 90-day outcomes, with adjusted odds of approximately 2.5, 3.2, and 2.7 times the odds of poor functional outcome (mRS scores of 3 to 6), respectively.
Receiver operating characteristic analysis showed that a perfusion threshold of 15 mL was associated with poor 90-day functional outcomes, with 45% sensitivity and 81% specificity in patients with mild stroke.
Among the patients with mild stroke, 74.8% had perfusion volumes of 0 to 10 mL, while 14% had volumes greater than 31 mL.
The investigators noted several limitations, including the retrospective design, potential selection bias as a result of the inclusion of only patients with available CT perfusion imaging, and the lack of standardization in perfusion thresholds across platforms. Although RAPID software was used to reduce variability, perfusion estimates may still differ depending on acquisition protocols and postprocessing methods.
“CT perfusion parameters can reveal tissue at risk even in patients with mild neurological deficits, allowing for early identification of those vulnerable to neurological deterioration and poor functional outcomes,” wrote lead study author Yohanna Kusuma, of the School of Medicine at Deakin University in Australia, and colleagues.
The study authors reported no conflicts of interest.