Does the National Institutes of Health Stroke Scale favor left hemisphere strokes?

Background and Purpose-The National Institutes of Health Stroke Scale (NIHS S) is a valid, reproducible scale that measures neurological deficit. Of 42 possible points, 7 points are directly related to measurement of language compared with only 2 points related to neglect. Methods-We examined the placebo arm of the NINDS t-PA stroke trial to test the hypothesis that the total volume of cerebral infarction in patients wit h right hemisphere strokes would be greater than the volume of cerebral inf arction in patients with left hemisphere strokes who have similar NIHSS sco res. The volume of stroke was determined by computerized image analysis of CT films and CT images Stored on computer tape and optical disks. Cube-root transformation of lesion volume was performed for each CT, Transformed les ion volume was analyzed in a logistic regression model to predict volume of stroke by NIHSS score for each hemisphere. Spearman rank correlation was u sed to determine the relation between the NIHSS score and lesion volume. Results-The volume for right hemisphere stroke was statistically greater th an the volume for left hemisphere strokes, adjusting for the baseline NIHSS (P<0.001). For each 5-point category of the NIHSS score <20, the median vo lume of right hemisphere strokes was approximately double the median volume of left hemisphere strokes. For example, for patients with a left hemisphe re stroke and a 24-hour NIHSS score of 16 to 20, the median volume of cereb ral infarction was 48 mt (interquartile range 14 to 111 mL) as compared wit h 133 mt (interquartile range 81 to 208 mLfor patients with a right hemisph ere stroke (P<0.001). The median volume of a right hemisphere stroke was ro ughly equal to the median volume of a left hemisphere stroke in the next hi ghest 5-point category of the NIHSS, The Spearman rank correlation between the 24-hour NIHSS score and 3-month lesion volume was 0.72 for patients wit h left hemisphere stroke and 0.71 for patients with right hemisphere stroke . Conclusions-For a given NIHSS score, the median volume of right hemisphere strokes is consistently larger than the median volume of left hemisphere st rokes. The clinical implications of our finding need further exploration.