Cerebellar superficial siderosis (SS) has been recently reported to be present in about 10% of both hereditary (n=50) and sporadic (n=46) cerebral amyloid angiopathy (CAA) patients on 3T MRI using susceptibility-weighted imaging (SWI) in the majority of patients. In that study, cerebellar SS was associated with a higher number of supratentorial lobar and superficial cerebellar macrobleeds (although cerebellar SS was not directly located adjacent to these cerebellar macrobleeds). It is unclear if cerebellar SS is caused by in situ leakage of cerebellar leptomeningeal vessels or rather represents hemorrhagic diffusion from cerebellar parenchymal micro/macrobleeds or from supratentorial bleeding sources via the tentorium cerebelli (TC).

Inclusion Criteria:

• CAA patients (according to the modified Boston criteria)
• with acute symptoms related to acute ICH, acute subarachnoid haemorrhage, or cortical SS

Exclusion Criteria:

• Patients with recent trauma,
• Patients with anticoagulation treatment,
• Patients with pathological blood coagulation tests (activated partial thromboplastin time [aPTT] ratio=patient's aPTT/normal control aPTT] >1.2; or partial thromboplastin time [PTT] <75%) or platelet count (<100 x 109/L)
• Patients with inflammatory CAA

Sporadic probable CAA patients (according to the modified Boston criteria) presenting with acute symptoms related to acute ICH, acute subarachnoid haemorrhage, or cortical SS, between September 2009 and January 2022 in Nîmes University Hospital, France