Swirl sign (intracranial hemorrhage)
Citation, DOI & article data
The swirl sign refers to the non-contrast CT appearance of acute extravasation of blood into a hematoma, for example an intracerebral hemorrhage, extradural hematoma or subdural hematoma. It represents unclotted fresh blood which is of lower attenuation than the clotted blood which surrounds it 1,5,6. It is in some ways the corollary of the spot sign on CTA which represents the same phenomenon, but in that case, caused by extraluminal focal accumulation/pooling/extravasation of contrast 2,5.
The swirl sign is only one or many imaging features described in an attempt to predict hematoma growth, and in many instances, these signs overlap.
For example, the black hole sign is in many respects a swirl sign that is A) encapsulated by the hematoma and B) >28 HU lower in density than the surrounding hematoma 6.
The swirl sign denotes one of more areas within, or in continuity with, the hematoma that are of lower attenuation than the surrounding/adjacent clot. This can vary from isoattenuating to hypoattenuating to the adjacent brain 6.
Their morphology is variable; truly swirly (curvilinear, streaklike), rounded or branching 6.
- 1. Al-Nakshabandi NA. The swirl sign. Radiology. 2001;218 (2): 433. doi:10.1148/radiology.218.2.r01fe09433 - Pubmed citation
- 2. Wada R, Aviv RI, Fox AJ et-al. CT angiography "spot sign" predicts hematoma expansion in acute intracerebral hemorrhage. Stroke. 2007;38 (4): 1257-62. doi:10.1161/01.STR.0000259633.59404.f3 - Pubmed citation
- 3. Das B, Khurana D, Ahuja CK. Bilateral "Swirl Sign": A predictor of rebleed. (2016) Annals of Indian Academy of Neurology. 19 (4): 514-515. doi:10.4103/0972-2327.194460 - Pubmed
- 4. Selariu E, Zia E, Brizzi M, Abul-Kasim K. Swirl sign in intracerebral haemorrhage: definition, prevalence, reliability and prognostic value. (2012) BMC neurology. 12: 109. doi:10.1186/1471-2377-12-109 - Pubmed
- 5. D. Ng, L. Churilov, P. Mitchell, R. Dowling, B. Yan. The CT Swirl Sign Is Associated with Hematoma Expansion in Intracerebral Hemorrhage. (2018) American Journal of Neuroradiology. doi:10.3174/ajnr.A5465 - Pubmed
- 6. Morotti A, Boulouis G, Dowlatshahi D et al. Standards for Detecting, Interpreting, and Reporting Noncontrast Computed Tomographic Markers of Intracerebral Hemorrhage Expansion. Ann Neurol. 2019;86(4):480-92. doi:10.1002/ana.25563 - Pubmed