Embolic shower

Last revised by Rohit Sharma on 15 Feb 2024

The term embolic shower is a commonly used radiological description of a specific pattern of ischemic stroke, however, it is poorly defined in the medical literature.

Embolic shower is usually used to describe numerous, bilateral, often small, acute ischemic strokes, involving multiple vascular territories seemingly at random, which have all occurred at one single or similar time point ref. The term can also be used more liberally, referring to emboli causing infarcts to multiple organs, however, this article will focus on its use in relation to ischemic stroke.

The term is typically employed with reference to a 'central' source of embolism as the cause for ischemic strokes. This is typically in relation to the heart (e.g. atrial fibrillation, infective endocarditis, during/after cardiac surgery), but may also include the aortic arch (e.g. aortic arch atheroma) 1-4. However, a similar pattern of acute ischemic stroke can also occur due to embolism from more distal arteries or other etiologies (e.g. hypercoagulable states from malignancy, cerebral fat embolism, hypotension) 1.

An embolic shower is best appreciated on MRI on diffusion weighted imaging 1, whereby the ischemic strokes are classically, but not exclusively, affecting the external (cortical) border zone 2. However, evidence of an embolic shower may also be appreciated on CT if the ischemic strokes are established and/or large enough, or if the emboli are calcific (known as the salted pretzel sign) 1,5.

The prognostic value of this radiological pattern is uncertain given there is no formally accepted definition for what constitutes an embolic shower. One study focusing on acute ischemic strokes involving multiple arterial territories, regardless of etiology, found that patients with this pattern of infarction were more likely to have altered conscious state, seizures, and generally poorer outcomes 1.

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