Modified NIH Stroke Scale (mNIHSS)

About the modified NIH Stroke Scale

The modified National Institutes of Health Stroke Scale (mNIHSS) is also a graded neurological examination, developed using formal clinometric analyses.

The modified NIHSS is a shortened version of the original NIHSS which has been shown to be equally, if not more accurate. It removes items 1A, 7 and 10 and combines items 3 and 4 into one, making the scale easier to use and time efficient, taking an average of 6 minutes to complete.

Items from the original NIHSS that have shown poor reliability include Level of Consciousness, Facial Palsy, Limb Ataxia, and Dysarthria. The changes brought to the scale through the modified version by Lyden et al. minimize redundancy and eliminate poorly reliable items.

Overall, only 29% of mNIHSS had less than excellent reliability, a significant decrease from 45% items with less excellent reliability in the original version. The mNIHSS also demonstrated validity using factor and coefficient analysis.

In a subsequent validation study of the mNIHSS against the NIHSS, an increase in good agreement was observed from 54% to 71% whilst poor agreement decreased from 12% to 5%.

The mNIHSS was found to be more reliable in multiple settings, including scores drawn from medical records or via telemedicine, and when used in clinical trials.

The improved reliability benefits alone may be enough to justify the transition to the mNIHSS. But there are other significant benefits. Due the unreliability of some of the NIHSS items, patients may score high on the original version in the case of mild strokes. There should be a significant difference between a score of 4 and a score of 8.

Alternatively, on the original version patients may score as mild even in the case of more severe deficits, because some items may remain unscored due to the aforementioned unreliability. This finding was replicated in patients deemed “too good to treat”. If a patient would score a 4, instead of their true 8, the clinician may be more likely to withhold rt-PA therapy. This intrinsic variability may result in different treatment behaviors, and different patient outcomes.

The sample picture, list of words, and sample sentences from the original NIHSS item 9 were not changed, and could continue to be used as necessary to help assess relevant scale elements.

Unfortunately, both the original and modified NIHSS fail to accurately or reliably detect patients with posterior circulation findings.

With the removal of the ataxia item 7, there may be concern that the mNIHSS would be even less able to assess brainstem type strokes but consensus is that, due to this item’s inherent poor reliability, the benefit of its presence may not outweigh the consistency of the mNIHSS.

It is also considered that other items of the mNIHSS (LOC, visual field, sensory and motor) could capture effects of posterior circulation.

Whilst at the time of publishing this, the original version remains the most prevalent (with tPA administration guidelines almost exclusively referencing the NIHSS), the predictive ability of the modified NIHSS continues to be investigated in research trials.

References

Original reference

Lyden PD, Lu M, Levine SR, Brott TG, Broderick J; NINDS rtPA Stroke Study Group. A modified National Institutes of Health Stroke Scale for use in stroke clinical trials: preliminary reliability and validity. Stroke. 2001 Jun;32(6):1310-7.

Validation

Meyer BC, Hemmen TM, Jackson CM, Lyden PD. Modified National Institutes of Health Stroke Scale for use in stroke clinical trials: prospective reliability and validity. Stroke. 2002 May;33(5):1261-6.

Other references

Meyer BC, Lyden PD. The Modified National Institutes of Health Stroke Scale (mNIHSS): Its Time Has Come. Int J Stroke. Aug 2009; 4(4): 267–273. doi: 10.1111/j.1747-4949.2009.00294.

Kasner SE, Cucchiara BL, McGarvey ML, Luciano JM, Liebeskind DS, Chalela JA. Modified National Institutes of Health Stroke Scale can be estimated from medical records. Stroke. 2003 Feb;34(2):568-70. PubMed PMID:12574577