Brain 18FDG-PET pattern in cognitively impaired elderly patients with bipolar disorder

Patients with bipolar disorder (BD) are at increased risk of dementia. The underlying mechanisms are debated. FDG-PET elucidates glucose metabolic reductions due to altered neuronal activity in the cerebral cortex, allowing detection and identification of neurodegenerative processes. This study aims to investigate cerebral glucose metabolism in cognitively impaired elderly patients with BD using FDG-PET imaging, to elucidate potential underlying mechanisms and improve diagnostic accuracy.

We conducted a retrospective analysis of FDG-PET scans from 32 cognitively impaired elderly patients with BD (mean age 70.4 years). These were compared with scans from 35 non-degenerative controls (NDC) and patients diagnosed with Alzheimer's disease (AD, n = 27), frontotemporal dementia (FTD, n = 26), and dementia with Lewy bodies (DLB, n = 18). Voxel-wise statistical analysis was performed using SPM software, adjusting for age and sex.

No significant cortical hypometabolism was found in patients with BD compared to NDC. In contrast, typical patterns of hypometabolism were observed in the AD, FTD, and DLB groups. The findings suggest that late-life cognitive impairment in patients with BD is not due to a single common neurodegenerative process.

The absence of abnormal cortical metabolism in cognitively impaired elderly patients with BD suggests that cognitive impairment in this population may not be driven by a common neurodegenerative pathway. Further studies using other biomarkers are needed to investigate the brain processes involved, which could lead to improved understanding and management of cognitive impairment in patients with BD.