Association of Preoperative Posterior Cingulate Cortex Microstructural Damage With Postoperative Delirium

BACKGROUND: Postoperative delirium is the most common postsurgical complication in older adults and is associated with an increased risk of long-term cognitive decline and Alzheimer's disease (AD) and related dementias (ADRD). However, the neurological basis of this increased risk-whether postoperative delirium unmasks latent preoperative pathology or leads to AD-relevant pathology after perioperative brain injury-remains unclear. METHODS: To investigate potential brain microstructural abnormalities associated with postoperative delirium and cognitive function, we analyzed pre- and post-operative Neurite Orientation Dispersion and Density Imaging (NODDI) MRI data within the posterior cingulate cortex (PCC) from 110 patients aged ≥60 years who underwent non-cardiac/non-intracranial surgery. RESULTS: We found increased free water (FISO) and decreased neurite density index (NDI) and orientation dispersion index (ODI) in the dorsal PCC before surgery among those who later developed postoperative delirium (n = 12) versus those who did not (n = 98). Preoperative dorsal PCC NDI and ODI values were also positively associated with preoperative attention/concentration performance, independent of age, education level, and global brain atrophy (NDI: = 0.29 (95% CI, 0.10-0.50), P = .008; ODI: = 0.29 (95% CI, 0.03-0.44), P = .004). Yet, these diffusion metrics were not correlated with cerebrospinal fluid amyloid beta (Aβ) positivity or levels. CONCLUSIONS: These results suggest that preoperative latent brain abnormalities within the dorsal PCC may underlie attention/concentration deficits and susceptibility to postoperative delirium, yet these dorsal PCC NODDI abnormalities were not significantly associated with CSF Aβ levels (a measure of brain Amyloid deposition). Our findings highlight microstructural vulnerability within the PCC, a key region of the default mode network, as a neuroanatomic locus that can help explain the link between preoperative attention/concentration deficits and increased postoperative delirium risk among vulnerable older surgical patients.