An exploratory research report on brain mineralization in postoperative delirium and cognitive decline

Abstract

Delirium is a severe postoperative complication associated with poor overall and especially neurocognitive prognosis. Altered brain mineralization is found in neurodegenerative disorders but has not been studied in postoperative delirium and postoperative cognitive decline. We hypothesized that mineralization‐related hypointensity in susceptibility‐weighted magnetic resonance imaging (SWI) is associated with postoperative delirium and cognitive decline. In an exploratory, hypothesis‐generating study, we analysed a subsample of cognitively healthy patients ≥65 years who underwent SWI before (N = 65) and 3 months after surgery (N = 33). We measured relative SWI intensities in the basal ganglia, hippocampus and posterior basal forebrain cholinergic system (pBFCS). A post hoc analysis of two pBFCS subregions (Ch4, Ch4p) was conducted. Patients were screened for delirium until the seventh postoperative day. Cognitive testing was performed before and 3 months after surgery. Fourteen patients developed delirium. After adjustment for age, sex, preoperative cognition and region volume, only pBFCS hypointensity was associated with delirium (regression coefficient [90% CI]: B = −15.3 [−31.6; −0.8]). After adjustments for surgery duration, age, sex and region volume, perioperative change in relative SWI intensities of the pBFCS was associated with cognitive decline 3 months after surgery at a trend level (B = 6.8 [−0.9; 14.1]), which was probably driven by a stronger association in subregion Ch4p (B = 9.3 [2.3; 16.2]). Brain mineralization, particularly in the cerebral cholinergic system, could be a pathomechanism in postoperative delirium and cognitive decline. Evidence from our studies is limited because of the small sample and a SWI dataset unfit for iron quantification, and the analyses presented here should be considered exploratory.

Postoperative Delirium and the Older Adult: Untangling the Confusion

“…22,23 In addition, hypointense areas in the cholinergic system were related to POD, possibly representing areas of iron deposition and calcifications, also seen in a range of neurodegenerative diseases. 24 Challenges such as diagnostic assessment method, frequency of evaluation, and constraints related to the collection of biomarkers all make this task difficult. 11 Several comorbidities that are more prevalent with aging are also risk factors for POD, further complicating specific POD marker recognition, and are the focus of multiple research teams.…”

“…Preoperative cortical brain infarcts, complex white matter hyperintensity, brain atrophy, and glymphatic system changes are examples of brain areas that could be used as surrogate markers for brain vulnerability 22,23 . In addition, hypointense areas in the cholinergic system were related to POD, possibly representing areas of iron deposition and calcifications, also seen in a range of neurodegenerative diseases 24 …”