We disagree with the recommendation to use the HINTS Exam as the gold standard for detecting posterior stroke from the April article titled, “How not to miss posterior circulation stroke.”¹ The usefulness of the HINTS exam is limited to patients who have underlying nystagmus, which represents less than a quarter of patients with posterior stroke. Instead, we advocate for use of the the National Institutes of Health Stroke Scale (NIHSS) combined with a test of skew and a test of gait to screen for stroke in patients presenting with dizziness, vertigo, ataxia, and imbalance.

Problems with HINTS

1. The HINTS exam requires underlying nystagmus.² In the setting of a patient with nystagmus, a normal response to the head impulse test (defined as the subject being able to keep eyes on target) can be sensitive for stroke.
2. Over 75 percent of patients with posterior stroke do not present with nystagmus so the HINTS exam cannot be used.³
3. The interrater reliability of the HINTS exam is, at best, moderate, and requires significant training to perform.^4,5

NIHSS: An Underrated Screen for Posterior Stroke

There is a widespread misconception that NIHSS is insensitive for posterior stroke. In fact, NIHSS is highly sensitive for stroke, because it contains multiple elements that directly test the brainstem, cerebellum, and occipital region.⁶ The sensitivity of detecting a stroke approaches or surpasses that of diffusion weighted MRI in the early phase, and unlike the HINTS exam, it is a useful screen in all patients with posterior stroke symptoms, not just those with nystagmus.^6,7,8

It is important to remember that the NIHSS was originally developed to quantify all stroke types, not just middle cerebral artery strokes. It is intended to capture as much functional and testable brain volume as possible, and redundant or unreliable elements were removed. Thus, it is applicable to interior circulation as well as posterior circulation strokes by its very design.⁹

Additionally, the NIHSS is the most commonly used screen for acute stroke and the majority of emergency clinicians know its elements and can perform the NIHSS with a high interrater reliability between emergency clinicians and neurologists.¹⁰

What Are the Gaps in the NIHSS?

The lack of balance testing has been noted as the most common reason for posterior strokes with NIHSS of zero. The authors thus recommend adding a test of truncal stability, which can also be tested with gait.¹¹

The NIHSS does not include a test of skew, which can be an important sign of posterior stroke. It is the most easily performable section of the HINTS exam and is applicable even when no nystagmus is present.

Screening at a National Scale: NIHSS Plus Test of Gait Plus Test of Skew

In 2020, we recommended that our clinicians perform NIHSS plus test of gait and test of skew in patients with undifferentiated dizziness, vertigo, ataxia, and imbalance, as well as any patient suspected of having a posterior stroke. Our mnemonic for this practice change is “dizziNIHSS,” which seems to resonate with our clinicians.

On a per patient volume basis from 2018–present, malpractice claims for missed posterior stroke presenting as undifferentiated dizziness have decreased by 50 percent (internal data), suggesting the NIHSS plus test of skew plus test of gait is effective in preventing posterior stroke misses and claims.

Summary

We advocate for the use of the NIHSS with a test of skew and test of gait to screen for stroke in patients presenting with dizziness, vertigo, ataxia, imbalance, and other clinical suspicion for posterior circulation stroke. This approach has strong evidence, is well accepted by clinicians, and has cut our predicted malpractice costs by 50 percent.

References

1. Pilcher C, Dajer T. How not to miss posterior circulation stroke. ACEP Now. Accessed June 1, 2024.
2. Tarnutzer AA, Berkowitz AL, Robinson KA,et al. Does my dizzy patient have a stroke? A systematic review of bedside diagnosis in acute vestibular syndrome. CMAJ. 2011 Jun 14;183(9):E571-92.
3. Searls DE, Pazdera L, Korbel E, et al. Symptoms and signs of posterior circulation ischemia in the new England medical center posterior circulation registry. Arch Neurol. 2012 Mar;69(3):346-51.
4. Henriksen AC, Hallas P. Inter-rater variability in the interpretation of the head impulse test results. Clin Exp Emerg Med. 2018 Mar 30;5(1):69-70.
5. Tarnutzer AA, Edlow JA. Bedside Testing in Acute Vestibular Syndrome-Evaluating HINTS Plus and Beyond-A Critical Review. Audiol Res. 2023 Sep 1;13(5):670-685.
6. Eskioglou E, Huchmandzadeh Millotte M, Amiguet M, Michel P. National Institutes of Health Stroke Scale Zero Strokes. Stroke. 2018 Dec;49(12):3057-3059.
7. Edlow BL, Hurwitz S, Edlow JA. Diagnosis of DWI-negative acute ischemic stroke: A meta-analysis. Neurology. 2017 Jul 18;89(3):256-262.
8. Kim K, Kim BJ, Huh J, et al. Delayed Lesions on Diffusion-Weighted Imaging in Initially Lesion-Negative Stroke Patients. J Stroke. 2021 Jan;23(1):69-81.
9. Dunning, K. (2011). National Institutes of Health Stroke Scale. In: Kreutzer, J.S., DeLuca, J., Caplan, B. (eds) Encyclopedia of Clinical Neuropsychology. Springer, New York, NY.
10. Cummock JS, Wong KK, Volpi JJ, et al. Reliability of the National Institutes of Health (NIH) Stroke Scale Between Emergency Room and Neurology Physicians for Initial Stroke Severity Scoring. Cureus. 2023 Apr 14;15(4):e37595.
11. Martin-Schild S, Albright KC, Tanksley J, et al. Zero on the NIHSS does not equal the absence of stroke. Ann Emerg Med. 2011 Jan;57(1):42-5.