Updated minimum criteria for identification of cortical superficial siderosis and acute convexity subarachnoid hemorrhage in the context of CAA and small-vessel disease5

Criteria
  • Well-defined, homogeneous hypointense curvilinear signal intensity (black) on T2*-GRE or SWI MRI in the superficial layers of the cerebral cortex, within the subarachnoid space, or in both

  • Blooming effect on T2*-GRE and SWI compared with T1- or T2-weighted sequences

  • Differentiation from multiple very superficial cortical cerebral microbleeds (small, generally 2–5 mm, well-defined, homogeneous, and either round or oval lesions, at least half surrounded by brain parenchyma)

  • If there is corresponding signal hyperintensity in the subarachnoid space on proton density–weighted or FLAIR sequences (or hyperdensity on CT, if available), the term “acute cSAH” should be used

  • Axial T1-weighted or FLAIR images should be used for anatomic confirmation of the gyral location of the signal hypointensities identified on T2*-GRE or SWI sequences

  • Absence of infratentorial (brain stem, cerebellum, spinal cord) siderosis

  • Ensure exclusion of potential hemorrhagic and nonhemorrhagic cSS mimics (eg, vessel flow voids, thrombosed vessels, petechial hemorrhagic transformation of infarcts, calcium deposits)

  • Consider all potential non-CAA secondary etiologies of cSS and acute cSAH

  • cSS should be categorized as focal or disseminated (eg, in line with the modified Boston criteria)

  • In each patient, the location (cerebral lobes and so forth) of cSS and the number of cerebral sulci affected can be recorded

  • Other relevant vascular neuroimaging lesions both remote from and in close proximity (eg, up to 1 cm) to cSS should be evaluated, using established standards (eg, cerebral microbleeds, acute small DWI lesions, and so forth)

  • Note:—GRE indicates gradient recalled-echo; cSAH, convexity SAH.