Swirl sign in intracerebral haemorrhage: definition, prevalence, reliability and prognostic value

Background: Swirl sign has previously been described in epidural hematomas as areas of low attenuation, radiolucency or irregular density. The aims of this study were to describe swirl sign in ICH, study its prevalence, study the reliability of the subjective evaluation on computed tomography (CT), and to explore its prognostic value. Methods: CTs of 203 patients with ICH were retrospectively evaluated for the presence of swirl sign. Association between swirl sign and different clinical and radiological variables was studied. Results: Inter-and intraobserver agreement with regard to the occurrence of swirl sign was substantial (kappa 0.80) and almost perfect (kappa 0.87), respectively. Swirl sign was found in 30% of the study population. 61% of patients with swirl sign were dead at one month compared with 21% of those with no swirl sign (p < 0.001). Only 19% of patients with swirl sign exhibited favorable outcome at three months compared with 53% of those with no swirl sign (p < 0.001). Patients with swirl sign exhibited larger ICHs with average ICH-volume 52 +/- 50 ml (median 42 ml) compared with 15 +/- 25 ml (median 6) in patients whose CT did not show swirl sign (p < 0.001). Swirl sign was independent predictor of death at one month (p = 0.03; adjusted odds ratio 2.6, 95% CI 1.1 - 6), and functional outcome at three months (p = 0.045; adjusted odds ratio 2.6, 95% CI 1.02 - 6.5). Conclusions: As swirl sign showed to be an ominous sign, we recommend identification of this sign in cases of ICHs.