Stroke mimics and chameleons

A stroke mimic is a situation in which a diagnosis of stroke at admission is not confirmed, and a stroke chameleon is a situation in which a stroke is revealed by clinical symptoms that are not usual in stroke. The objective of this review is to identify the most frequent clinical situations in which stroke mimics and chameleons are encountered and consequences for the patient.

The safety profile of intravenous thrombolysis (IVT) in patients who have stroke mimics is excellent, and intracranial hemorrhages are rare. Modern neuroimaging techniques help identifying most mimics. For stroke chameleons the role of imaging may be less important, especially when the clinical presentation is not suggestive of a brain disorder that request immediate neuroimaging. Education of health providers to identify such situations is crucial.

Stroke mimics account for up to 25% of admissions for probable strokes. The proportion of patients with stroke mimics decreases with use of MRI at baseline. Mimics cannot always be ruled out in emergency. The problem with mimics is that stroke facilities are not properly used, and patients may receive IVT. However, thrombolysis is usually well tolerated in mimics and we should not spend much time in all patients to improve diagnostic accuracy, knowing that the time lost is harmful in all patients, and will only prevent treating one mimic out of 100 patients. The problem with chameleons is more serious, because patients are not identified, and are not properly treated.