What Does "Favorable" Mean for Stroke Scores Less Than 6?
For stroke patients with NIHSS scores less than 6, a "favorable" outcome is most commonly defined as a modified Rankin Scale (mRS) score of 0-1, representing complete independence with no symptoms or no significant disability despite symptoms. 1
Understanding the Terminology
The stroke literature uses specific, standardized definitions for outcomes based on the modified Rankin Scale:
"Excellent" outcome = mRS 0-1: No symptoms (mRS 0) or no significant disability despite symptoms; able to carry out all usual activities independently (mRS 1) 1
"Good" outcome = mRS 2: Slight disability; able to look after own affairs without assistance but unable to perform some previous activities (e.g., cannot drive a car or dance) 1
"Poor" or "Unfavorable" outcome = mRS 3-6: Ranges from moderate disability requiring some help, to severe disability requiring constant care, to death 1
Why This Matters for Low NIHSS Scores
The distinction is clinically critical because patients with NIHSS scores ≤5 are often labeled as "mild stroke," yet 25-30% still end up with unfavorable outcomes (mRS 2-6). 2 This creates a treatment dilemma, as these patients are frequently excluded from thrombolysis despite having substantial risk of disability.
Specific Cutoffs for Low NIHSS Patients:
- NIHSS 0-1: More than 80% achieve favorable outcome (mRS 0-1) without intervention 2
- NIHSS 2-3: Approximately 25-30% risk of unfavorable outcome 2
- NIHSS 4-5: Higher risk of disability, with treatment showing benefit (OR 1.53 for achieving mRS 0-1 with thrombolysis) 3
Common Pitfall to Avoid
Do not confuse "favorable" with "good." While some studies use mRS 0-2 as a favorable outcome threshold, the most rigorous definition—and the one used in landmark trials like NINDS—defines favorable as mRS 0-1 only. 1 Using mRS 0-2 as "favorable" can obscure the fact that mRS 2 patients still have meaningful disability preventing them from returning to all previous activities.
The Evidence Shows Inconsistency
A systematic review found that 56% of stroke trials use valence terms like "favorable" or "good," but apply them inconsistently across different mRS ranges. 4 The term "good outcome" has been applied to five different outcome ranges in various studies, creating confusion. This is why you must always specify the exact mRS score range when discussing outcomes.
Practical Application
When evaluating a patient with NIHSS <6:
NIHSS 0-1 with isolated symptoms (LOC, gaze, facial palsy, sensory, or dysarthria only): >80% achieve mRS 0-1; generally considered truly "minor" 2
NIHSS 2-5: Substantial risk of mRS ≥2; should not automatically be excluded from acute treatment 3, 2
NIHSS 4-5 specifically: Treatment with thrombolysis shows clear benefit for achieving mRS 0-1 3
The 2015 ACEP Clinical Policy explicitly states that "excellent" functional outcome equals mRS 0-1, which should be your reference standard when discussing favorable outcomes in low NIHSS stroke patients. 1