SWI versus GRE-T2: Assessing cortical superficial siderosis in advanced cerebral amyloid angiopathy

Cortical superficial siderosis (cSS) is a key neuroimaging marker of cerebral amyloid angiopathy (CAA) detected on blood-sensitive magnetic resonance imaging (MRI). We aimed to assess cSS in advanced CAA patients and explore differences in its evaluation between susceptibility weighted imaging (SWI) and gradient recalled echo-T2* (GRE-T2*). Neuroimaging data gathered from a prospective cohort of CAA patients with probable or definite CAA were retrospectively analyzed by two independent raters. SWI and GRE-T2* were used to assess presence and severity (absent, focal [≤3 sulci] or disseminated [>3 sulci]) of cSS and number of foci. Ratings were compared between sequences and inter-rater agreement was determined. Post hoc analysis explored differences in cSS multifocality scores. We detected cSS in 38 patients with SWI and in 36 with GRE-T2* (70.4% versus 66.7%; P=0.5). The two raters agreed in detecting more disseminated cSS when using SWI: 16 focal (29.63%) and 20 disseminated (37.04%) cases of cSS seen on GRE-T2* and 11 (20.37%) focal and 27 (50%) disseminated cSS cases seen using SWI (P=0.008). Inter-rater agreement was equivalent for the two sequences (κpresence 0.7 versus 0.69; κseverity 0.74 versus 0.66) for assessing both presence and severity of cSS. Post hoc analysis showed higher multifocality scores from both raters’ SWI evaluations, with agreement equivalent to that for T2* evaluations. Our findings suggest that SWI ratings could show more disseminated cSS and higher multifocality scores in advanced CAA patients with inter-rater reliability equivalent to that obtained using GRE-T2*, regardless of level of experience.