Introduction: When encountering a suspected stroke patient in the emergency room, stroke code activation should occur. However, it is challenging to distinguish patients with acute stroke (AS) in a short time in an emergency. We aimed to determine the frequency and characteristics of stroke mimics (false positive cases) and stroke chameleons (false negative cases), and identify the key clinical features. Methods: All consecutive patients admitted in the emergency room with stroke code between 2016 and 2017 were included for the analysis. Patients with a sudden onset of neurological deficit in a time window less than 8 hours were accepted in the stroke code pathway. After a neurological evaluation and brain MRI imaging, stroke mimics were determined by an expert neurologist. To distinguish stroke chameleons, we retrospectively reviewed all patients with acute ischemic stroke from the prospectively constructed acute stroke registry (Korean Stroke Registry of Seoul National University Hospital). Stroke chameleons were defined as failure to suspect stroke or incorrect exclusion of stroke at the emergency department. Results: The mean age of included patients was 65.7, and 57.1 % were male. Among the all included patients, 443 patients were correctly diagnosed as AS, 205 patients were non-stroke patients (stroke mimics), and 37 patients were missed stroke code activation (stroke chameleons) at the initial screening. The positive predictive value of stroke code activation was 68.4%, and the sensitivity was 92.3%. In the stroke mimics, the most frequent discharge diagnosis was epilepsy (19.5%), brain tumor (10.2%), drug-related encephalopathy (9.8%), and metabolic encephalopathy (8.3%). In the stroke chameleons, the initial diagnosis was mistaken for non-stroke for the following reasons: only dizziness symptoms (32.4%), visual symptoms (13.5%), and headache (8.1%). Conclusions: While over-diagnosis of stroke can result in an economic burden on patients, the failure to diagnosis stroke may preclude time-sensitive treatments. This study demonstrated that the frequency and characteristics of stroke mimics and chameleons. These findings may be used to raise awareness in emergent setting to recognize and treat such patients appropriately.
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