VACEP's EBM Series: Timely Identification of Posterior Circulation Ischemic Stroke in the Emergency Department
VACEP Evidence-Based Medicine for General Emergency Physicians Series
Authors: Andrea L. Klein, MD, MPH & Andrew B. Moore, MD, MCR | Virginia Tech Carilion School of Medicine and Health Sciences Department of Emergency Medicine
Reviewer: Paola Cordero-Colon, MD & Winston Wu, MD | UVA Health Department of Emergency Medicine
The VACEP Evidence-Based Medicine Review Series allows Virginia emergency medicine residents and attendings to share and analyze a recent peer-reviewed clinical study. You can also read the full article, Posterior National Institutes of Health Stroke Scale Improves Prognostic Accuracy in Posterior Circulation Stroke, from the AHA/ASA Journals’ December 2021 edition.
CASE
A 67-year-old male active smoker with a history of hypertension, hyperlipidemia, and type 2 diabetes mellitus presents for evaluation one hour after the acute onset of balance issues and nausea. This has never happened before. The patient is unable to walk forwards or backwards without losing balance because “it feels like I am on a boat.”
Triage vitals are notable for a blood pressure of 220/104 mmHg otherwise within normal limits.
NIH stroke score is 0.
Neurological exam is negative for nystagmus, dysmetria, or any other focal neurological deficit. Dix Hallpike maneuver is negative.
Do you activate your emergency department’s stroke team for this patient?
STUDY SUMMARY
Posterior strokes account for 20-25% of ischemic strokes in the United States and carry a substantially higher morbidity and mortality than anterior ischemic stroke (Kim et al. 2016).
Most emergency department stroke protocols, however, utilize the anterior circulation-centric NIH stroke score (NIHSS) to activate their stroke team.
Given the time-sensitive nature of intravenous thrombolytics and recent advances in posterior endovascular interventions, there is clearly room for improvement in emergency department triage of possible posterior ischemic stroke patients (Sommer et al. 2018).
The recently published Society of Academic Emergency Medicine (SAEM) Guidelines for Reasonable and Appropriate Care in the Emergency Department (GRACE) article on dizziness promotes the HINTS exam (Head Impulse Test, Characterization of Spontaneous Nystagmus, Test of Skew) as the most sensitive and specific physical exam cluster to detect posterior stroke in patients presenting with active dizziness (Edlow et al. 2023).
It is important to note, however, that the HINTS exam is only appropriate to use in patients with ongoing nystagmus and is only reliable if performed by providers well-trained in this complex exam.
Two points highlighted in a study that found inappropriate use of the HINTS exam by urgent care and primary care providers resulted in a two-fold increase in MRIs ordered within a healthcare system — with no improvement in posterior stroke detection (Adams et al. 2022).
Furthermore, fewer than 25% of posterior ischemic strokes present with nystagmus, limiting the sensitivity of the HINTS exam (Searls et al. 2012).
Other scoring systems have been developed in very small prospective trials, including the Adam’s Scale of Posterior Stroke (ASPOS) score (Wisniewski et al 2021), the Israeli Vertebrobasilar Stroke Scale (IVBSS) (Wisniewski et al 2021), and the expanded NIHSS (eNIHSS) (Olivato et al. 2016).
exploring alternatives
One alternative to HINTS is the newly developed and not yet externally validated (only internally validated) posterior-NIHSS, which assesses patients’ using the traditional anterior circulation NIHSS plus three additional items: gait/truncal ataxia (5 points), dysphagia (4 points), and cough (3 points) (Alemseged et al. 2021).
Figure 1. Clinical Features Associated with Poor Outcome in Derivation Cohort.
Gait ataxia is assessed by instructing the patient to stand with their feet together for several seconds before taking several steps forward naturally.
Truncal ataxia is assessed in patients too weak to walk by testing whether or not the patients could maintain a seated position without assistance (sit up straight).
Dysphagia is assessed by a speech therapist in the original study.
Cough is assessed using a three-step protocol in which the patient must be able to swallow their own saliva and must have no anatomical abnormalities such as palatal paralysis or tongue deviation.
HOW THE STUDY WORKED
The study retrospectively analyzed 202 posterior circulation stroke patients from The Basilar Artery Treatment and Management (BATMAN) registry, an international database on posterior circulation strokes with contributing sites in North America, Europe, Asia, and Australia (Alemseged et al. 2017). Using the Modified Rankin Score (mRS) as the metric for comparing “good” and “poor” functional outcomes, the study group identified gait/truncal ataxia, dysphagia, and poor cough as the strongest predictors of poor outcome (Figure 1).
About the EBM Review Series
This is a literature review series started by the University of Virginia’s Josh Easter, MD, MSc, a VACEP board member working to connect the academic community in Virginia. We invite each residency in Virginia (and D.C.) to create a faculty/resident team to submit and review articles. Sign up to submit one.
Goals
Provide a brief monthly synopsis of a high yield article germane to the practice of emergency medicine for distribution to all VACEP members
Provide an opportunity for a peer reviewed publication and invited presentation for faculty and trainees
Foster an academic community focused on evidenced based medicine for emergency medicine residency programs in the region
The study group then internally validated these three predictive factors in 65 prospectively recruited posterior strokes at BATMAN (Basilar Artery on Computed Tomography Angiography) study sites and confirmed that of the factors measured in this study to predict good and poor outcomes, gait/truncal ataxia, dysphagia, and poor cough are indeed the strongest predictors.
Subgroup analysis proved that a higher posterior NIHSS was correlated with higher likelihood of undergoing mechanical thrombectomy. In other words, higher posterior NIHSS scores are more likely to be associated with large vessel occlusions of the posterior circulation.
LIMITATIONS
The posterior NIHSS has limitations, namely that it was derived retrospectively in a small cohort of 202 patients and required the presence of a speech language pathologist (SLP) in triage to accurately complete.
Larger prospective studies are underway to externally validate the score and additional work will need to be done to identify equally sensitive dysphagia and cough tests that do not require an SLP to perform, as SLPs are not readily available in most emergency departments.
SUMMARY
As emergency physicians, our primary role in stroke care is appropriately triaging and identifying stroke patients eligible for time-sensitive thrombolytic and endovascular therapies (in addition to safely supporting the airway, breathing, and circulation of these patients during initial resuscitation).
In its current state, the posterior NIHSS is certainly a step in the right direction towards identifying intervention-eligible patients with posterior stroke. The main practical issue with this scale, however, is that its additional items include clinical signs that we often already associate with severe intracranial pathology (dysphagia and cough) and are not specific to posterior stroke. It is therefore likely that in prospective validation, this scoring system will prove to be much more sensitive than specific.
In summary, there is still significant need for prospective validation of a clinical decision tool to identify posterior circulation strokes.
So far, the posterior NIHSS is the most robustly derived and internally validated scoring system available.
Given the absence of any other tool at this time, the emergency medicine community should become acquainted with the posterior NIHSS and consider implementing it (or some variation) in their department and institution’s stroke protocol so that these severely debilitating and potentially lethal pathologies do not go unrecognized.
While the American Heart Association has not provided a formal recommendation on posterior stroke scales yet, the stroke committee at the author’s institution is actively discussing integrating the posterior NIHSS into its initial stroke activation process.
based on the study, HERE’S WHAT YOU DO
Your suspicion for a posterior stroke is high, and you perform additional testing using the posterior NIHSS. The patient scores 10/12 on the posterior NIHSS and is activated as a stroke alert at your institution. CT head is negative for hemorrhage, and CT angiogram demonstrates an acute basilar artery occlusion. Thrombolytics are administered after his blood pressure is controlled, and the patient is taken to the angio suite for mechanical thrombectomy. He is successfully recanalized, makes a full neurological recovery, and is able to return home to his family the next week with no functional deficit.
