Iris sign

Last revised by Daniel J Bell on 22 Jun 2021

The iris sign is the imaging appearance of deep medullary venous thrombosis/congestion-related white matter injury in neonates created by fan-shaped, outwards radiating hemorrhages or cytotoxic edema in the subcortical and periventricular cerebral white matter. The appearance resembles the flower of the iris plant.

The sign is recognized on multiple modalities 1-4. On cranial ultrasound, the affected areas appear hyperechoic. On non-contrast CT, they appear hyperattenuating. Susceptibility weighted imaging and diffusion weighted MR imaging demonstrate hypointensities and hyperintensities, respectively, in this configuration.

The iris sign commonly occurs in association with subpial hemorrhage 2, suggesting a common pathophysiology.

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