Background and Purpose—Intravenous thrombolysis for acute ischemic stroke is usually based on clinical assessment, blood test results, and CT findings. Intravenous thrombolysis of stroke mimics may occur but has not been studied in detail.

Methods—We determined frequency, clinical characteristics, and outcome of mimic patients versus patients with stroke treated with intravenous thrombolysis using data of a prospective, single-center thrombolysis data bank.

Results—Among 250 patients, 243 (97.2%) had strokes and 7 (2.8%) were mimics. Seizure was the most frequent diagnosis among mimics. There was a trend toward lower National Institutes of Health Stroke Scale scores in mimics (9.9±4.2) compared with strokes (13.7±5.4; P=0.06). Global aphasia without hemiparesis was the presenting symptom in 3 (42.9%) mimics versus 8 (3.3%) strokes (P=0.002). Orolingual angioedema, symptomatic intracranial hemorrhage, and asymptomatic intracranial hemorrhage occurred in 3 (1.2%), 13 (5.3%), and 30 (12.3%) patients with stroke, but were absent in mimics. After 3 months, 6 (85.7%) mimics and 86 (35.4%) strokes had a modified Rankin Scale score of 0 to 1 (P=0.01).

Conclusions—Only few patients receiving intravenous thrombolysis did eventually have a final diagnosis other than stroke, ie, mostly seizures. Their outcome was favorable. Although clinical features differed between the stroke and the mimic groups, the differences were not distinctive enough to allow assigning individual patients to either of the groups. Multimodal neuroimaging or electroencephalographic recordings may be helpful for this assignment. However, their potential benefit has to be weighed against the potential harm of delayed thrombolysis.