Preoperative thalamus volume is not associated with preoperative cognitive impairment (preCI) or postoperative cognitive dysfunction (POCD)

Abstract

A growing body of literature suggests the important role of the thalamus in cognition and neurodegenerative diseases. This study aims to elucidate whether the preoperative thalamic volume is associated with preoperative cognitive impairment (preCI) and whether it is predictive for postoperative cognitive dysfunction at 3 months (POCD). We enrolled 301 patients aged 65 or older and without signs of dementia who were undergoing elective surgery. Magnetic resonance imaging was conducted prior to surgery. Freesurfer (version 5.3.) was used to automatically segment the thalamus volume. A neuropsychological test battery was administered before surgery and at a 3 month follow-up. It included the computerized tests Paired Associate Learning (PAL), Verbal Recognition Memory (VRM), Spatial Span Length (SSP), Simple Reaction Time (SRT), the pen-and-paper Trail-Making-Test (TMT) and the manual Grooved Pegboard Test (GPT). Using a reliable change index, preCI and POCD were defined as total Z-score > 1.96 (sum score over all tests) and/or Z-scores > 1.96 in ≥ 2 individual cognitive test parameters. For statistical analyses, multivariable logistic regression models were applied. Age, sex and intracranial volume were covariates in the models. Of 301 patients who received a presurgical neuropsychological testing and MRI, 34 (11.3%) had preCI. 89 patients (29.5%) were lost to follow-up. The remaining 212 patients received a follow-up cognitive test after 3 months, of whom 25 (8.3%) presented with POCD. Independently of age, sex and intracranial volume, neither preCI (OR per cm³ increment 0.81 [95% CI 0.60-1.07] p = 0.14) nor POCD (OR 1.02 per cm³ increment [95% CI 0.75-1.40] p = 0.87) were statistically significantly associated with patients' preoperative thalamus volume. In this cohort we could not show an association of presurgical thalamus volume with preCI or POCD.Clinical Trial Number: NCT02265263 ( https://clinicaltrials.gov/ct2/show/results/NCT02265263 ).

Figure 1

‘Strengthening the Reporting of Observational Studies in Epidemiology’ (STROBE) diagram. The flow chart shows reasons displays the inclusion process until the follow-up at 3 months. Reasons for exclusion are presented in gray boxes.

Figure 2

Boxplots of thalamus volume across groups. Thalamus volume in cm³ is displayed on the y-axis, while the different groups are placed on the x-axis: the entire cohort analysed in this study (n = 301 (all) in black, patients with preoperative cognitive impairment (preCI) in pink and patients with postoperative cognitive dysfunction (POCD) in green. Coloring was selected according to colorblind safe standards.