Background: Prior studies have shown a correlation between the National Institutes of Health Stroke Scale (NIHSS) score and infarct volume on diffusion weighted imaging (DWI); however data are limited in patients with minor stroke whose treatment is controversial. Our aim is to determine the association between DWI lesion(s) volume and the (1) total NIHSS score and (2) NIHSS components in a population of patients with minor ischemic stroke.
Methods: We included all patients with minor stroke (NIHSS 0-5) who were enrolled in the prospective Stroke Warning Information and Faster Treatment (SWIFT) study. All patients were admitted to the hospital with a final diagnosis of stroke. We calculated lesion(s) volume (cm3) on DWI sequence using Medical Image Processing, Analysis, and Visualization (MIPAV, NIH, Version 7.1.1). Based on the distribution of lesion volume, we summarized the explanatory value into median cm3. We used non-parametric tests to study the association between the primary outcome, DWI lesion(s) volume, and the predictors (NIHSS score and its components).
Results: 894 patients had a discharge diagnosis of ischemic stroke; 709 underwent MRI and 510 were DWI positive. There was a weak graded relationship between NIHSS score and median DWI lesion volume in cm3: (NIHSS 0: 7.1, NIHSS 1: 8.0, NIHSS 2: 17.1, NIHSS 3: 11.6, NIHSS 4: 19.0, NIHSS 5: 23.6). We also noted highly significant relationships between lesion volume and certain NIHSS components. Compared to patients without the deficit, the median lesion volume was significantly higher in patients with neglect (105.6 vs. 12.5,p=0.025), language disorder (34.6 vs. 11.9,p<0.001), and visual field deficits (185.6 vs. 11.6,p<0.001). Other components of the NIHSS were not associated with lesion volume.
Conclusion: In patients with minor stroke, the nature of the neurological deficit improves prediction of infarct volume when added to the total NIHSS score. This may lead to clinical and therapeutic implications.