What causes the island sign in intracerebral hemorrhage on computed tomography?
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Answer:
The island sign is a reliable non-contrast CT imaging marker that independently predicts hematoma expansion and poor clinical outcome in patients with spontaneous intracerebral hemorrhage (ICH). It represents a special type of extremely irregularly shaped hematoma characterized by multifocal small bleeding foci (“islands”) separate from and surrounding the main hematoma. The underlying pathophysiology suggests that the main hematoma represents bleeding from a ruptured vessel, while the peripheral islands of blood reflect continued or multifocal hemorrhage from damaged adjacent arterioles. In the original cohort, the island sign was observed in 44.7% of patients with documented hematoma expansion and demonstrated a specificity of 98.2% for predicting expansion, with a positive predictive value of 92.7%. When adjusted for other clinical variables (age, Glasgow Coma Scale score, intraventricular hemorrhage, subarachnoid hemorrhage, admission systolic blood pressure, baseline ICH volume, infratentorial location), the island sign remained an independent predictor of poor functional outcome.
Why is it called so?
The sign is named for its radiographic appearance of small, isolated clusters of blood (representing multifocal bleeding) separate from the main central hematoma, resembling islands scattered around a larger landmass.
Pathophysiology
The island sign develops when active or recurrent bleeding occurs from damaged vessels adjacent to the primary hematoma, creating satellite foci of hemorrhage in the surrounding tissue that appear disconnected from the main clot on axial CT sections. This multifocal bleeding pattern indicates ongoing vascular disruption and hemostatic failure, distinguishing it from simple irregular hematoma margins, and suggests more aggressive bleeding dynamics with greater likelihood of continued hematoma expansion.
Alternative names: None
Other associated named signs: Satellite sign (bleeding foci not entirely separate from the main hematoma), blend sign and black hole sign (density-based non-contrast CT markers of ICH expansion), and the CT angiography spot sign (a distinct, contrast-based predictor of hematoma expansion)
References
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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The island sign arises from multifocal secondary vessel rupture and active hematoma propagation, producing satellite hemorrhages around the main intracerebral hematoma, which appear as isolated “islands” on CT.
Correct!
thanks for your quick response