National Institutes of Health Stroke Scale

Stroke severity may be stratified on the basis of NIHSS scores as follows (Brott et al, 1989):

• Very Severe:  >25

• Severe: 15 – 24

• Mild to Moderately Severe: 5 – 14  

• Mild: 1 – 5 

Acute Stroke: (Schlegel et al, 2003; Rundek et al, 2000)

Outcomes related to NIHSS scores at admission:

• Scores of <5; 80% of stroke survivors will be discharged to home

• Score between 6 and 13 typically require acute inpatient rehabilitation

• Scores of >14 frequently require long-term skilled care

Acute Stroke: (Williams et al, 1999; n = 34, first stroke, patients assessed 1 and 3 months (+/- 1 week) after stroke)

Acute Stroke: (Goldstein & Samsa, 1997; 4 patients assessed by 30 physicians and 29 study coordinators; 3 months between assessments)

• Excellent test-retest reliability; ICC = 0.93

Acute Stroke: (Goldstein & Samsa, 1997)

• Excellent interrater reliability; ICC = 0.95

Acute Stroke: Interrater Agreement (Goldstein et al, 1989; n = 20 with 2 independent observers)

• Adequate to Excellent agreement was found for 9 of the 13 items on the NIHSS (Kappa = 0.32 to 0.79); lowest levels of agreement were found for the Facial palsy (Kappa = 0.22) and limb ataxia (Kappa = -0.16) items.

(Oh et al., 2012; n=19 with 21 raters Korean version of the NIHSS (K-NIHSS)).

• Excellent interrater reliability; ICC=0.998. Lowest levels of agreement were found for Facial paresis (Kappa = 0.439) and dysarthria (Kappa = 0.465) and highest for consciousness commands (0.950) and sensory function (0.911)..

• Excellent intrarater reliability; ICC=0.969

Hindi version of NIHSS (Prasad et al, 2012; n=107 with 2 raters)

• Excellent interrater reliability; ICC=0.995

Acute Stroke: Predictive validity (Adams et al, 1999; n = 1268)

• NIHSS scores at baseline predicted outcome at 7 and 90 days

• An excellent outcome was achieved by nearly two-thirds of the survivors who scored 3 or less at day 7

• Only a few patients who scored more than 15 at baseline achieved excellent outcomes after 90 days

Acute Stroke: Predictive validity (Baird et al, 2001; n = 66; <48 hours post-stroke)

• NIHSS combined with Magnetic Resonance Diffusion-Weighted imaging (MR DWI) and volume of ischaemic brain tissue on MR DWI significantly predicted stroke recovery

Acute Stroke: (Bohannon et al, 2002; n = 92, mean age = 70.0 (12.4) years; NIHSS was administered while patients were still in the emergency department, prior to admission)

• Poor* (but significant) correlation with length of stay (r = 0.276)
• Adequate* correlation with hospital charges (r = 0.320)
• Adequate* correlation with discharge destination (home or elsewhere) (r= - 0.355)

*Significant at p < 0.05

Acute Stroke: Concurrent Validity (Fink et al, 2002)

• Adequate to Excellent correlations with diffusion weighted MRI lesion volumes (r = 0.48 right, r = 0.58 left); and perfusion-weight hypoperfusion volumes (r = 0.62 right, r = 0.60 left)

Chronic Stroke: Concurrent Validity (Peters, et al., 2015)

• Examined the concurrent validity of the NHISS with the Stroke Impact Scale. No association between NIHSS and SIS-physical dimension (Spearman's rho = -.036; p=.666). SIS-overall perception of recovery (Spearman's rho = -.039; p=.640) nor SIS ADL/IADL score (Spearman's rho = -.054; p=.520).

Predictive Validity

• K-NIHSS at baseline (within 7 days of stroke onset) and modified Rankin Scale at 90-days post-onset was significantly positively correlated (Spearman's ρ=0.600; p<0.001).

• K-NIHSS significantly negatively correlated with the Barthel Index for the same time period (Spearman's ρ=-0.647; p<0.001).

• Hindi version (HV_NIHSS; Prasad et al., 2012, n=107 patients with stroke) and

Glasgow Coma Scale at 3 months are highly correlated (Spearman’s rho= -0.863, p<0.001)

• HV_NIHSS and Barthel Index at 3 months (Spearman’s rho: -0.829, p<0.001)

• HV_NIHSS and Modified Rankin Scale at 3 months (Spearman’s rho: 0.851, p<0.001)

Acute Stroke: (Schlegel et al, 2003; Rundek et al, 2000)

Outcomes related to NIHSS scores at admission:

• Scores of <5; 80% of stroke survivors will be discharged to home

• Score between 6 and 13 typically require acute inpatient rehabilitation

• Scores of >14 frequently require long-term skilled care

(Oh et al., 2012 n=207, patients with acute ischemic stroke Korean Version of the NIHSS (K-NIHSS))

Construct Validity determined by comparison with the Glasgow Coma Scale (Spearman ρ=-6.71; p<0.001) and deemed acceptable.

Items are based on components of a standard neurological examination (Kasner, 2006)

(Oh et al., 2012) Korean Version of the NIHSS (K-NIHSS)

Used the Content Validity Index (CVI) which is the proportion of expert raters (n=11) rating an item higher than 3 points on a 4-point ordinal rating scale; a rating of 1 denotes an irrelevant item, and a rating of 4 denotes an extremely relevant item. Ten of the NIHSS items received a 1.0 meaning that all of the expert raters, rated that item higher than a 3. The visual fields item received a CVI of 0.91 as one rater, rated that item a "2" in terms of relevancy. Items with a CVI of at least 0.78 are accepted as valid (Lynn; 1986). The means scores of the CVI for each item ranged from 3.46-3.73.

Acute Stroke:

• Floor effects are less commonly reported in the literature to date
• Ceiling effects (Pickard et al, 2005) A ceiling effect was observed at 6 months with the NIHSS effecting 20% of patients who completed the measure

Acute Stroke: (Brott et al, 1989)

NIHSS scores were compared to infarction size (measured by computed tomography) on 65 patients at 1 week post stroke. 10 items demonstrated an average of 25% change over 7 days. However, changes in limb ataxia and best gaze may have been overstated.