The susceptibility vessel sign is a radiological sign appreciated on susceptibility-sensitive MRI brain sequences that is described in patients with acute ischemic stroke. It correlates well with the hyperdense vessel sign (e.g. hyperdense MCA sign) that may be seen on CT brain, but is considered more sensitive 1.
The sign describes hypointense blooming artifact seen on GRE or SWI MRI brain sequences within an occluded intracranial artery, indicating thrombus, that exceeds the size of the contralateral normal artery diameter 1. It is a sign seen commonly in patients with large vessel occlusion eligible for endovascular clot retrieval, with a positive susceptibility vessel sign seen in up to 87.5% of patients imaged prior to endovascular clot retrieval 2.
The susceptibility vessel sign occurs due to the thrombus being erythrocyte-rich, which results in the presence of paramagnetic deoxyhemoglobin within the thrombus, leading to signal loss on susceptibility-sensitive MRI brain sequences such as GRE or SWI 1-6. Because oxyhemoglobin eventually degrades into deoxyhemoglobin within an erythrocyte-rich thrombus, the presence or not of the susceptibility vessel sign may be impacted on the timing of imaging in relation to the symptom onset of stroke, and is thought to become positive within 1-8 hours of symptom onset 1,5,6.
A positive or negative susceptibility vessel sign has a number of clinical implications:
in many studies and a meta-analysis, a positive susceptibility vessel sign was associated with higher rates of successful recanalization after endovascular clot retrieval in anterior circulation ischemic strokes 1-4
a positive susceptibility vessel sign may be associated with better functional outcomes independent of recanalization outcomes 1-4
there is conflicting evidence regarding outcomes in patients with a positive susceptibility vessel sign in relation to intravenous thrombolysis 2
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there is conflicting evidence regarding a positive susceptibility vessel sign and the etiology of the ischemic stroke
while many studies initially suggested an association between a positive susceptibility vessel sign with cardioembolic stroke, this has been contradicted in more recent literature 1,2,7
there is suggestion that absence of the susceptibility vessel sign may be associated with an underlying malignancy driving a prothrombotic state as stroke etiology 7 or with intracranial atherosclerotic disease 8
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