A smaller amygdala is associated with anxiety in Parkinson’s disease – a combined FreeSurfer-Voxel-based-morphometry study

Chapter Two – A smaller amygdala is associated with anxiety in Parkinson's disease – a combined FreeSurfer-Voxel-based-morphometry study under review Two A smaller amygdala is associated with anxiety in Parkinson's disease – a combined FreeSurfer-Voxel-based-morphometry study Abstract Up to 50 percent of all Parkinson's disease (PD) patients develop symptoms of anxiety during the course of their illness, a percentage that is much higher than in the general population. This suggests that pathological alterations associated with PD partly underlie these symptoms. So far only a limited amount of studies has been conducted on the neural correlates of anxiety in PD. The goal of the present cross-sectional study in 110 early stage PD patients (age: 64.6±10.3 years) was to investigate the association between anxiety symptoms and volume of the hippocampus and amygdala, structures that play an important role in the processing of emotional stimuli and have previously been associated with anxiety in the general population. We used both FreeSurfer and voxel-based morphometry (VBM) for the volumetric analyses. Both the FreeSurfer (β =-0.24, P=.001) and VBM (r =-0.23, P=.016) analyses showed a negative correlation between the severity of anxiety symptoms (measured with the Beck Anxiety Inventory) and volume of the left amygdala. This association was independent of the severity of motor symptoms, autonomic dysfunction and medication status and was predominantly driven by the psychological symptoms of anxiety. These results confirm previous studies in the general population showing lower left amygdalar volume in anxious patients. Whether this volume decrease constitutes a premorbid trait, a Parkinson-associated neurobiological susceptibility to anxiety or the consequence of chronic anxiety symptoms remains to be determined by future prospective longitudinal studies. Nonetheless, we tentatively hypothesize that the Parkinson pathology is responsible for the volume loss of the amygdala and the concomitant development of anxiety symptoms.