Perioperative covert stroke (i.e. a stroke with clinical manifestation) occurs in up to 1% of in-patient non-cardiac surgeries and is associated with increased mortality and disability. Covert stroke (i.e. brain infarcts without acute clinical manifestation) is generally more common than overt stroke and associated with dementia and cognitive decline. The prevalence of covert stroke in the setting of non-cardiac surgery has never been investigated so far. The NeuroVISION investigators prospectively collected data from > 1000 patients aged 65 years or older undergoing elective non-cardiac surgery in 12 centres over 9 countries. All patients underwent brain MRI between days 2 and 9 after surgery and were daily screened for delirium in the first 3 days after surgery. In addition, 1 year after surgery all patients were contacted and interviewed. The primary outcome of this study was cognitive decline from baseline to 1 year follow-up. The mean age of participants was 73 years, 56% were men, and 55 patients died in the year after surgery. Covert stroke was documented in 7% of all patients and the primary outcome, cognitive decline after 1 year, occurred in 42% of all participants with covert perioperative stroke compared to 29% of patients without covert stroke. The occurrence of a perioperative stroke doubled the risk of a postoperative delirium and quadruplet the risk of an overt cerebrovascular event during the first year after surgery. Besides covert stroke, only age was another risk factor for cognitive decline.
A decline in cognitive function is one of the most feared complications for an individual patient. The study highlights that not only clinically acute manifest brain injuries count. Also silent events will ask their toll in later life. Additional efforts are necessary not only to prevent overt stroke but also to reduce the incidence of covert events.