Perioperative ischaemic brain injury and plasma neurofilament light: a secondary analysis of two prospective cohort studies

Background: Ischaemic brain infarction can occur without acute neurological symptoms (covert strokes) or with symptoms (overt strokes), both associated with poor health outcomes. We conducted a pilot study of the incidence of preoperative and postoperative (intraoperative or postoperative) covert strokes, and explored the relationship of post-operative ischaemic brain injury to blood levels of neurofilament light, a biomarker of neuronal damage.Methods: We analysed 101 preoperative (within 2 weeks of surgery) and 58 postoperative research MRIs on postoperative days 2-9 from two prospective cohorts collected at the University of Wisconsin (NCT01980511 and NCT03124303). Par-ticipants were aged >65 yr and undergoing non-intracranial, non-carotid surgery.Results: Preoperative covert stroke was identified in 2/101 participants (2%; Bayesian 95% confidence interval [CI], 0.2-5.4). This rate was statistically different from the postoperative ischaemic brain injury rate of 7/58 (12%, 4.9-21.3%; P=0.01) based on postoperative imaging. However, in a smaller group of participants with paired imaging (n=30), we did not identify the same effect (P=0.67). Patients with postoperative brain injury had elevated peak neurofilament light levels (median [inter-quartile range], 2.34 [2.24-2.64] log10 pg ml -1) compared with those without (1.86 [1.48-2.21] log10 pg ml -1; P=0.025). Delirium severity scores were higher in those with postoperative brain injury (19 [17-21]) compared with those without (7 [4-12]; P=0.01).Conclusion: Although limited by a small sample size, these data suggest that preoperative covert stroke occurs more commonly than previously anticipated. Plasma neurofilament light is a potential screening biomarker for postoperative ischaemic brain injury.

Automated summary

This pilot study examined the incidence of preoperative and postoperative covert strokes and the relationship between postoperative brain injury and neurofilament light levels. The findings suggest that preoperative covert stroke may occur more frequently than expected, and plasma neurofilament light could be a potential biomarker for postoperative brain injury.