BackgroundWe present a case illustrating evolution of symptoms and brain magnetic resonance imaging in cortical superficial siderosis.Case presentationA 74-year-old man with no prior medical history presented with transient focal neurological episodes with subtle imaging changes. There was no evidence of cortical superficial siderosis. Two weeks later, the patient was readmitted with new episodes, and had developed cortical superficial siderosis adjacent to a cerebral microbleed. Transient focal neurological episode secondary to cortical superficial siderosis was diagnosed together with probable cerebral amyloid angiopathy.ConclusionClinical symptoms may precede the development of cortical superficial siderosis prior to being detectable on brain MRI. This case highlights the temporal development of cortical superficial siderosis.