We related composition of cerebral thrombi to stroke subtype and attenuation on non-contrast CT (NCCT) to gain more insight in etiopathogenesis and to validate thrombus attenuation as a new imaging biomarker for acute stroke.

We histopathologically investigated 22 thrombi retrieved after mechanical thrombectomy in acute stroke patients. First, thrombi were classified as fresh, lytic or organized. Second, percentages of red blood cells (RBCs), platelets and fibrin and number of red, white (respectively RBCs or platelets outnumbering other components with ≥15%) or mixed thrombi were compared between large artery atherosclerosis (LAA), cardioembolism, dissection and unknown subtype. Third, correlation between attenuation and RBCs, platelets and fibrin was calculated using Pearson's correlation coefficients (r).

Thrombi were fresh in 73% (n = 16), lytic in 18% (n = 4) and organized in 9% (n = 2). The stroke cause was LAA in eight (36%), cardioembolism in six (27%), dissection in three (14%), and unknown in five (23%) patients. LAA thrombi showed the highest percentage RBCs (median 50 (range 35–90)), followed by dissection (35 (20–40), p = 0.05), cardioembolism (35 (5–45), p = 0.013) and unknown subtype (25 (2–40), p = 0.006). No differences in platelets (p = 0.16) and fibrin (p = 0.52) between subtypes were found. LAA thrombi were classified as red or mixed (both n = 4), cardioembolisms as mixed (n = 5) or white (n = 1) and dissection as mixed (n = 3). There was a moderate positive correlation between attenuation and RBCs (r = 0.401, p = 0.049), and weak negative correlations with platelets (r = −0.368, p = 0.09) and fibrin (r = −0.073, p = 0.75).

The majority of cerebral thrombi is fresh. There are no differences in age of thrombi between subtypes. LAA thrombi have highest percentages RBCs, cardioembolism and unknown subtype lowest. No relationship exists between subtype and platelets or fibrin percentages. We found a correlation between the RBC-component and thrombus attenuation, which improves validation of thrombus attenuation on NCCT as an imaging biomarker for stroke management.