Cognitive screening improves the in predictive value of stroke severity scores for functional outcome 3-6 months after mild stroke and transient ischaemic attack: an observational study

Objectives: To investigate the prognostic value of the neurocognitive status measured by screening instruments, the Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE), individually and in combination with the stroke severity scale, the National Institute of Health Stroke Scale (NIHSS), obtained at the subacute stroke phase or the baseline (<= 2 weeks), for functional outcome 3-6 months later. Design: Prospective observational study. Setting: Tertiary stroke neurology service. Participants: 400 patients with a recent ischaemic stroke or transient ischaemic attack (TIA) received NIHSS, MoCA and MMSE at baseline and were followed up 3-6 months later. Primary outcome measures: At 3-6 months following the index event, functional outcome was measured by the modified Rankin Scale (mRS) scores. Results: Most patients (79.8%) had a mild ischaemic stroke and less disability (median NIHSS=2, median mRS=2 and median premorbid mRS=0), while a minority of patients had TIA (20.3%). Baseline NIHSS, MMSE and MoCA scores individually predicted mRS scores at 3-6 months, with NIHSS being the strongest predictor (NIHSS: R-2 change=0.043, p<0.001). Moreover, baseline MMSE scores had a small but statistically significant incremental predictive value to the baseline NIHSS for mRS scores at 3-6 months, while baseline MoCA scores did not (MMSE: R-2 changes=0.006, p=0.03; MoCA: R-2 changes=0.004, p=0.083). However, in patients with more severe stroke at baseline (defined as NIHSS>2), baseline MoCA and MMSE had a significant and moderately large incremental predictive value to the baseline NIHSS for mRS scores at 3-6 months (MMSE: R-2 changes=0.021, p=0.010; MoCA: R-2 changes=0.017, p=0.021). Conclusions: Cognitive screening at the subacute stroke phase can predict functional outcome independently and improve the predictive value of stroke severity scores for functional outcome 3-6 months later, particularly in patients with more severe stroke.