CT-NIHSS mismatch does not correlate with MRI diffusion-perfusion mismatch.

BACKGROUND AND PURPOSE

MRI diffusion-perfusion mismatch may identify patients for thrombolysis beyond 3 hours. However, MRI has limited availability in many hospitals. We investigated whether mismatch between the Alberta Stroke Program Early CT Score (ASPECTS) and the NIH Stroke Scale (NIHSS) correlates with MRI diffusion-perfusion mismatch.

METHODS

We retrospectively analyzed a cohort of consecutive acute ischemic stroke patients who underwent MRI and CT at admission. NIHSS was performed by the admitting physician. MRI and CT were reviewed by 2 blinded expert raters. Degree of MRI mismatch was defined as present (> 25%) or absent (<25%). Univariate and multivariate analyses were performed to determine characteristics associated with MRI mismatch. Probability of MRI mismatch was calculated for all combinations of ASPECTS and NIHSS cutoff scores.

RESULTS

Included in the analysis were 143 patients. Median NIHSS on admission was 4 (IQR, 2 to 10); median ASPECTS was 10 (IQR, 9 to 10). Median time to completion of MRI and CT was 4.5 (2.5 to 13.9) hours after onset. CT and MRI were separated by a median of 35 (IQR, 29 to 44) minutes. MRI mismatch was present in 41% of patients. In multivariate analysis, only shorter time-to-scan (OR, 0.96 per hour; 95% CI, 0.92 to 1.0; P=0.043) was associated with MRI mismatch. There was no combination of NIHSS and ASPECTS thresholds that was significantly associated with MRI mismatch.

CONCLUSIONS

ASPECTS-NIHSS mismatch did not correlate with MRI diffusion-perfusion mismatch in this clinical cohort. MRI mismatch was associated with decreasing time from stroke onset to scan.