Silent brain injury after cardiac surgery: a review: cognitive dysfunction and magnetic resonance imaging diffusion-weighted imaging findings.

The appearance of cognitive dysfunction after cardiac surgery in the absence of focal neurologic signs, a poorly understood but potentially devastating complication, almost certainly results from procedure-related brain injury. Confirmation of the occurrence of perioperative silent brain injury has been developed through advances in magnetic resonance imaging (MRI) techniques. These techniques detect new brain lesions in 25% to 50% of patients after both coronary artery bypass graft and valve surgery. Use of post-operative cognitive dysfunction as a marker of brain injury is problematic because of potential difficulties in ascertainment. It can be hypothesized that post-operative appearance of MRI lesions may serve as a more objective marker of brain injury in research efforts. If MRI examination can be used in this way, then 2 vitally important questions can be addressed. 1) What is the frequency of important, but silent, brain injury during cardiac surgery? 2) Does long-term cognitive impairment ensue? This review briefly discusses clinical features of post-operative cognitive dysfunction and reviews the evidence supporting a possible association with MRI evidence of perioperative brain injury and its potential for long-term dementia. We conclude that this association is plausible, but not yet firmly established.