LOS ANGELES—Laterality is an independent predictor of endovascular thrombectomy in patients with an NIH Stroke Scale (NIHSS) score of 12 or lower, according to research described at the 70th Annual Meeting of the American Academy of Neurology. “There may be a need for a laterality-based NIHSS score or at least a conscious effort to look for right-hemisphere strokes with a large-vessel occlusion,” said Shashvat Desai, MD, a neurology trainee at the University of Pittsburgh.
Endovascular thrombectomy is the standard of care for acute ischemic stroke resulting from a large-vessel occlusion. Among the eligibility criteria for thrombectomy is an NIHSS score of 6 or higher.
“The NIHSS score is biased and will allow a higher score for dominant-hemisphere strokes, as compared with nondominant-hemisphere strokes,” said Dr. Desai. “Seven points on this scale are directly related to language, which is a dominant-hemisphere function, and only two points are for neglect, which occurs during nondominant-hemisphere strokes.”
A Retrospective Data Analysis
To test their hypothesis that NIHSS score hemispheric lateralization bias affects stroke patient selection for acute endovascular thrombectomy, Dr. Desai and colleagues analyzed data from consecutive patients with acute ischemic stroke resulting from large-vessel occlusion who were admitted to a comprehensive stroke center between June 2015 and December 2016. Eligible patients were identified within 24 hours of when they were last known to be well, were functionally independent at baseline, had an Alberta Stroke Program Early CT (ASPECT) score of 6 or higher, and had an NIHSS score of 6 or higher.
The investigators included 211 patients in their study. They examined variables such as age, NIHSS score, occlusion location, baseline modified Rankin Scale (mRS) score, time to presentation, and treatment received. When they separated patients with left-hemisphere strokes from those with right-hemisphere strokes, they found that the two groups were well matched in terms of age, gender, and site of occlusion. The median admission NIHSS score was 19 for left-hemisphere strokes and 15 for right-hemisphere strokes, and the difference between groups was statistically significant.
Thrombectomy Was More Common for Left-Hemisphere Strokes
Endovascular thrombectomy was performed for 87% of left-hemisphere strokes, compared with 78% of right-hemisphere strokes, and the difference between groups was statistically significant. When the researchers examined only participants with a low NIHSS score (ie, 12 or lower), they found that thrombectomy was performed in 81% of left-hemisphere strokes, compared with 52% of right-hemisphere strokes. The difference in the rate of treatment was statistically significant. Among patients with a high NIHSS score (ie, higher than 12), endovascular therapy was performed in 88% of participants, regardless of laterality.
A regression analysis that included variables such as age, sex, occlusion location, time to presentation, ASPECT score, IV t-PA, and laterality indicated that laterality was the sole and independent predictor of receiving endovascular thrombectomy in patients with low NIHSS score. “The preservation of language in right-hemisphere strokes with low NIHSS score reduces the chances of receiving endovascular thrombectomy,” said Dr. Desai.
Among patients with low NIHSS scores who received thrombectomy, the rate of good outcome (ie, an mRS score of 0 to 2) at three months was 88% for left-hemisphere strokes and 71% for right-hemisphere strokes. This difference was not statistically significant, however. Among all patients with low NIHSS scores, irrespective of treatment, 86% of left-hemisphere strokes had a good outcome, compared with 48% of right-hemisphere strokes. This difference was statistically significant.