Abstract

Background: Stroke chameleons (SC), are often diagnosed too late in their course to benefit from intravenous thrombolysis (IVT) treatment in the Emergency Room (ER). It remains unclear what proportion of this patient population would be a candidate for IVT. We sought to identify the proportion of SC patients with contraindications to IVT and to delineate what those contraindications are. Methods: All consecutive SC patients who presented to the ER at a single center in Santiago Chile were evaluated between December 2014 and October 2023. Results: A total of 1193 S patients were evaluated, of which sixty-three (5.2 %, 95 %CI 4.1-6.6) were diagnosed as SC (mean age 59 +/- 21.3 years, 32 (50.7 %) women). The median NIHSS was 1 (IQR 1-3) and 50 (79.3 %) patients had an NIHSS <= 3. Of the 63 SC patients, 14 (22.2 %) were determined to be IVT candidates. In the remaining 49 patients, 71 contraindications for IVT were present: 28 patients had 1 contraindication, 20 patients had 2 contraindications, and 1 patient had 3 contraindications. The most common contraindication was absence of deficits measurable by NIHSS or very mild deficits in 31 (49.2 %) patients. This was followed by being outside of the therapeutic window for thrombolysis in 30 (47.6 %) patients. Both of these contraindications were present in 14 (22.2 %) patients. The most common erroneous diagnoses that SC patients received on presentation the ER were metabolic encephalopathy (11, 17.4 %), seizure disorder (9, 14.2 %), and migraine (7, 11.2 %). Conclusions: More than two thirds of SC patients presented to the ER with contraindications to IVT. The most frequent contraindications included deficits not measurable by NIHSS, extremely mild deficits, and being out of therapeutic window.