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See related article, p 2728 In this issue, Sommer et al present data from the 38-center Austrian Stroke Registry collaboration about functional outcome differences after posterior circulation stroke (PCS) versus anterior circulation stroke (ACS). As described, the aims of the present study were to analyze functional outcome differences between PCS and ACS patients and whether prolonged prehospital delays and stroke location had specific effect on those outcomes. The authors matched 4604 PCS and 4604 ACS patents based on National Institutes of Health Stroke Scale (NIHSS) scores, tPA (tissue-type plasminogen activator) treatment, premorbid modified Rankin Scale scores, stroke pathogenesis, demographic factors, and vascular risk factors. Functional outcome status at 3 months was better for ACS patients compared with PCS patients, especially for patients whose onset to arrival time was unknown or beyond 270 minutes. There was no difference in outcomes for ACS or PCA patients who presented earlier than 270 minutes or who were treated with tPA. In fact, because ACS and PCS patients were matched for time to presentation, time delay was not the primary explanation for the outcome differences. Furthermore, beneficial outcomes with endovascular therapy for PCS versus ACA paralleled those of intravenous tPA; because the database preceded widespread endovascular therapy, there were limits to exploration of differences in the large vessel occlusion subgroups treated by endovascular therapy, however. Previously, in 2017, the Austrian Stroke Registry group reported that PCS was associated with delays in door-to-needle time compared with ACS. In that study, 71 010 patients were entered into the registry between 2003 and 2015 of whom there were 11 924 PCS patients and 59 086 ACS patients. PCS symptom onset to arrival time was longer (170 minutes for PCS versus 110 minutes for ACS [P<0.001]) and door-to-needle time was also delayed (57 versus 45 minutes [P<0.001]). Thus, data from these 2 studies do suggest that PCS is associated with prehospital delays, compared with ACS and that these delays may still be partly responsible for worse outcomes in PCS patients. PCS are frequently under-recognized. Symptoms associated with PCS that may lead to under-recognition include nonfocal or nonspecific symptoms, such as nausea and vomiting, imbalance, and ill-defined dizziness. Admittedly, isolated vertigo, or dizziness, is an uncommon cause of stroke. In one series, stroke or TIA was diagnosed in only 3.2% of patients with dizziness. Imbalance was associated with a higher prediction of cerebrovascular events. In that series, however, (as in clinical practice) many patients did not undergo neuroimaging, raising the possibility that PCS-associated dizziness may be underestimated. Also, unilateral symptoms may not be present at the time of presentation. Thus, patients with PCs may be mistakenly thought to have seizures, drug overdoses, and other acute toxic or metabolic encephalopathies. Furthermore, under-recognition of PCS may also be associated with underassessment of clinical severity, which is the most likely explanation for the differences seen in the present study. The NIHSS is widely used for assessment of acute stroke patients, but the NIHSS is heavily weighted towards hemispheric disease, and with its focus of language function, even more heavily weighted toward left hemisphere versus the right hemisphere stroke. Symptoms such as vertigo, dysphagia, or gait disturbance, or associated findings of nystagmus, cranial nerve palsies, or truncal ataxia and gait imbalance, are not adequately assessed by the NIHSS. This assessment problem could have partly explained large differences in time to large vessel occlusion diagnosis in a small series where the median time from emergency department arrival to diagnosis was 504 minutes for basilar artery occlusion versus 83 minutes for left middle cerebral artery occlusion. This problem could also explain the outcome differences in the present study in which ACS and PCS were severity matched by NIHSS because PCS patients often present with lower NIHSS scores, and PCS deficits may be more disabling than ACS-related deficits for a given NIHSS score. In 1 study, 76% of PCS infarctions presented with NIHSS scores <6, and 71% of those patients had a baseline NIHSS score ≤4, yet 15% of those patients with stroke had a poor functional outcome at 3 months. That study noted a 4-point spread in the NIHSS for outcome predictions between ACS (8) and PCS; the >80% sensitivity cutoff for detecting patients with a subsequent poor outcome was an NIHSS of 4 for ACS but only 2 for PCS. In the current article, Sommer et al also note that previous studies reported variable outcomes for PCS, with some earlier small studies suggesting better functional outcomes compared with ACS and other studies reporting worse outcomes. In particular, they cite 1 multicenter study where there were worse outcomes for PCS versus ACS with mild NIHSS scores again reflecting the fact that the NIHSS is weighted more toward ACS symptoms and tends to underestimate stroke severity in PCS. The opinions expressed in this article are not necessarily those of the editors or of the American Heart Association. From the Departments of Neurology and Neurosurgery, Stritch School of Medicine, Loyola University Chicago, IL. Correspondence to Michael J. Schneck, MD, Loyola University Medical Center, Maguire Bldg, Suite 2700, 2160 S First Ave, Maywood, IL 60153. Email [email protected] Current Stroke Scales May Be Partly Responsible for Worse Outcomes in Posterior Circulation Stroke