Defining mild stroke: outcomes analysis of treated and untreated mild stroke patients

Background: Mild deficit is a relative contraindication to administration of intravenous recombinant tissue plasminogen activator (IV rtPA) for acute ischemic stroke. However, what constitutes "mild" deficit is vague. Prior studies showed patients with mild strokes have substantial disability rates at hospital discharge and at 90 days. We investigated whether the application of a new definition altered the rates of disability overall and assessed the effects of thrombolysis.

Methods: This analysis included all adult acute ischemic stroke patients from a prospective registry of consecutive patients (University of California San Diego Specialized Programs of Translational Research in Acute Stroke (SPOTRIAS) database, 2003-2014) with 90-day modified Rankin Scale (mRS) score available who were defined as "mild" using either: National Institutes of Health Stroke Scale (NIHSS) 0-5 or a "Re-examining Acute Eligibility for Thrombolysis" (TREAT) Task Force definition (NIHSS 0-5 and nondisabling based on prespecified syndromes). Dichotomized 90-day mRS were compared between treated and untreated patients using the 2 definitions.

Results: Of 802 ischemic stroke patients with mRS scores available, 184 had baseline mRS (0) and met TREAT criteria; 45 (24.5%) were rtPA treated. Among the treated patients, 35.6% had 90-day mRS (2-6), versus 28.8% in the untreated group, a nonsignificant difference after adjusting for baseline NIHSS (P = .47). None of the 45 treated patients had symptomatic hemorrhage. Outcomes were similar using the simpler NIHSS 0-5 definition.

Conclusions: About one third of mild stroke patients were not functionally independent at 90 days, irrespective of treatment or mild definition applied, calling into question the treatment efficacy of IV rtPA for mild strokes and what constitutes an appropriate definition of "mild." Randomized studies are necessary to determine rtPA treatment efficacy in mild stroke patients.