Edward P. Sloan, MD, MPH, FACEP, is Professor Emeritus of Emergency Medicine at the University of Illinois Chicago, Medical Director of the Physician Assistant Studies Program at Dominican University, and President and Board Chair of the Foundation for Education and Research in Neurological Emergencies (FERNE).
This educational series is based on Dr. Sloan’s presentation on Emergency Department acute ischemic stroke, stroke mimics, and stroke chameleons, presented at the Emergencies in Medicine conference in Park City, Utah, on March 2, 2026. The material was subsequently updated through August 2026 to incorporate important newer evidence relevant to emergency stroke care.
This topic is particularly important for the emergency physician because acute ischemic stroke remains one of the most time-critical diagnoses in emergency medicine. Clinicians must rapidly determine whether a patient with an acute neurological syndrome has true CNS ischemia, a stroke mimic that resembles AIS, or a stroke chameleon, a patient who actually has cerebral ischemia but presents atypically, potentially causing the stroke diagnosis to be missed. At the same time, the opportunity to provide timely reperfusion therapy to eligible patients must be preserved.
Part 1 FERNE Clinical Update
The first aspect of this series is a clinical update of the material presented at Emergencies in Medicine on March 2, 2026. It focuses on practical bedside questions for the emergency physician: How can AIS be distinguished from common stroke mimics? Which patients are at greatest risk of being stroke chameleons? How should mild or transient deficits, posterior circulation symptoms, dizziness and acute vestibular syndrome, low NIHSS scores, and initially negative imaging be approached? And when AIS remains clinically likely, how should diagnostic uncertainty influence the decision to provide IV thrombolysis?
Part 2 FERNE Journal Club and Evidence Update
The second aspect is a FERNE journal club and evidence update. The original clinical concepts and older foundational publications were compared with important recent 2025–2026 publications addressing the same clinical questions. Rather than simply identifying newer articles, the literature was examined to determine whether contemporary evidence supports, strengthens, modifies, or challenges the earlier clinical recommendations.
The literature spans both foundational studies from approximately 2013–2014 and contemporary studies from 2025–2026, allowing examination of how the evidence has evolved and, importantly, where newer studies continue to support earlier observations. The evidence addresses stroke-mimic frequency and characteristics, stroke chameleons, posterior circulation ischemia, acute dizziness, thrombolysis in mimics, telestroke and drip-and-ship care, and unusual high-risk mimics.
Central Clinical Question
Ultimately, both parts of this series address one central challenge for the emergency physician:
How can emergency physicians rapidly recognize and treat true acute ischemic stroke, identify important stroke mimics, avoid missing stroke chameleons, and preserve timely reperfusion therapy despite unavoidable diagnostic uncertainty?
The goal is not absolute diagnostic certainty before treatment. The goal is rapid, disciplined, evidence-based clinical decision-making that optimizes neurological outcomes while minimizing unnecessary risk.