Can 90-Day NIHSS Be Used for Outcome Assessment in TIA and Minor Stroke Studies?

Discussion Despite no quantifiable impairment on the NIHSS, a proportion of subjects with TIA or minor stroke were disabled at 3 months. Stroke in the posterior circulation increased the risk of achieving NIHSS 0 despite having some disability. Potential explanations include the presence of gait ataxia or cranial nerve palsies, which are not well captured by the NIHSS. This finding is concordant with the observation that patients with stroke in the posterior circulation tend to have lower NIHSS at presentation [4, 5] , while having a significant risk of disability [6] . Another limitation of NIHSS includes a bias towards higher scores in left hemispheric strokes. With small numbers of patients, we were not able to assess this in our study. Finally, patients may be affected by cognitive decline or mood disorders, which demand detailed assessment. We suggest that NIHSS should not be used on its own when assessing outcome in this population. It remains unclear as to what the most appropriate tools are with regard to measuring disability in TIA and minor stroke patients. Background Patients with TIA and minor stroke present a significant risk of disability at 3 months. Despite mild symptoms at presentation, up to 15% of patients will have a disabled outcome [1] . Historically, studies that focused on this population used recurrent stroke as the primary outcome in trials. In comparison, studies in moderate to severe strokes frequently use disability as principal end-points. Disability is often measured using the modified Rankin Scale (mRS), whereas neurological impairment is assessed using the National Institute of Health Stroke Scale (NIHSS). In this specific population, it remains unclear which outcome scale is preferable to capture subtle deficits [2] . We aimed at determining whether the 90 days NIHSS was a reasonable outcome measure in TIA and minor stroke patients.