Index event of cerebral amyloid angiopathy (CAA) determines long-term prognosis and recurrent events (retrospective analysis and clinical follow-up)

Background: The modified Boston criteria (mBC) define the probability for the diagnosis of cerebral amyloid angiopathy (CAA). Its initial clinical presentation differs from asymptomatic cerebral microbleedings (cMBs), acute ischemic stroke (AIS), cortical hemosiderosis (cSS), to lobar ICH (lICH). Methods: Retrospective analyses and clinical follow-ups of individuals with at least mBC "possible" CAA from 2005 to 2018. Results: 149 patients were classified in subgroups due to the index event: lICH (n = 91), AIS (n = 32), > 3 cMBs only (n = 16) and cSS (n = 10). Patients in the lICH subgroup had a significantly higher percentage of single new lICHs compared to other groups, whereas patients in the AIS- group had a significantly higher percentage of multiple new AIS. cMBs as index event predisposed for AIS during follow up (p < 0.0016). Patients of the cMBs- or cSS-group showed significantly more TFNEs (transient focal-neurological episodes) and lower numbers of asymptomatic patients (for epilepsy and TFNEs) at the index event than patients with lICH or AIS (p < 0.0013). At long-term follow-up, the cMBs- and cSS-group were characterized by more TFNEs and fewer asymptomatic patients. Conclusions: A new classification system of CAA should add subgroups according to the initial clinical presentation to the mBCs allowing individual prognosis, acute treatment and secondary prophylaxis.