Swirl sign (intracranial haemorrhage)
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View Frank Gaillard's current disclosuresAt the time the article was last revised Kieran Kusel had no financial relationships to ineligible companies to disclose.
View Kieran Kusel's current disclosures- Swirl appearance in intracranial haemorrhage
The swirl sign refers to the non-contrast CT appearance of acute extravasation of blood into a haematoma, for example an intracerebral haemorrhage, extradural haematoma or subdural haematoma. 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.
In an intracerebral haemorrhage, the swirl sign is one of many predictors of haematoma expansion 5 (see intracerebral haemorrhage for further discussion).
Terminology
The swirl sign is only one of many imaging features described in an attempt to predict haematoma 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 haematoma and B) >28 HU lower in density than the surrounding haematoma 6.
Radiographic features
CT
The swirl sign denotes one or more areas within, or in continuity with, the haematoma 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.
Quiz questions
References
- 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
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