S, Malt UF. Patterns of altered regional brain glucose metabolism in borderline personality disorder and bipolar II disorder.Objective: The relationship between borderline personality disorder (BPD) and bipolar II disorder (BIP-II) is disputed but understudied. Here, we investigated brain glucose metabolism in these patient groups and healthy control subjects (HCs). Methods: Sixty-five subjects, 22 BPD (19 females), 22 BIP-II (17 females), and 21 HC (14 females), were examined using 2-deoxy-2[18F]-fluoro-dglucose positron-emission tomography (PET) scanning. Only patients without reciprocal comorbidity were recruited; BPD participants without bipolar spectrum pathology; BIP-II participants without cluster A/B personality pathology. Groups were compared pairwise. Associations with mood state and childhood trauma were analyzed. Results: Both patient groups exhibited hypometabolism compared with HCs in insula, brainstem, and frontal white matter. Additionally, BPD patients showed hypometabolism in hypothalamus, midbrain, and striatum; BIP-II patients in cerebellum. Uncorrected analyses showed cortical areas of higher metabolism in BIP-II than BPD, and associations with clinical variables differed between the groups. Conclusion: Reduced metabolism in the insula regions was shown in both disorders, suggesting shared pathophysiological mechanisms. The observed patterns of altered metabolism specific to each patient group, as well as the uncorrected results, may also suggest differential pathophysiology. However, these latter findings must be interpreted cautiously given the non-significant corrected results in the direct comparison between the disorders.
Significant outcomes• This is the first FDG-PET study comparing patients with borderline personality disorder and patients with bipolar II disorder.• Several regions of decreased metabolism, including insula and frontotemporal white matter, were common for both disorders.• Reduced metabolism in the hypothalamus was shown in borderline patients only. This finding could potentially be linked to several previously suggested endocrinological disturbances in this disorder, involving HPA-axis, oxytocin, and testosterone.• Uncorrected analyses showed differences between the disorders regarding correlation with clinical variables.
Limitations• Most participants were on psychotropic medication. • The number of participants was limited, although comparable with previous PET studies of these patient groups.