Reduced volume of the mediodorsal and anteroventral thalamus is associated with anxiety in Parkinson's disease: A cross-sectional 7-tesla MRI study

BACKGROUND: Parkinson's disease (PD)-related anxiety occurs frequently and may be associated with imbalance between anxiety-related circuits. While the thalamus is a shared region of these circuits, its role in PD-related anxiety has not been explored so far. OBJECTIVE: To identify changes in volume of the thalamus and its subnuclei in patients with PD-related anxiety. METHODS: Cognitively intact PD patients (n = 105) were divided into two groups based on their score on the Parkinson anxiety scale (PAS): 31 PD patients had anxiety (Anx-PD) and 74 did not have anxiety (non-Anx-PD). Forty-five healthy control subjects were included. Participants underwent 7-Tesla MRI scanning. Using automatic segmentation, the volumes of the thalamus and its subnuclei were measured, compared between the groups and regressed on the PAS. RESULTS: The volumes of the thalamus and its subnuclei did not significantly differ between the groups. However, in anxious PD patients, more severe anxiety was strongly associated with a smaller volume of the right medial thalamic subregion, specifically the right mediodorsal magnocellular nucleus and the right mediodorsal parvocellular nucleus (R = 0.63, ß = -0.546, p-value = 0.007 and R = 0.60, ß = -0.547, p-value = 0.016, respectively), and of the left anteroventral thalamus (R = 0.73, FDR p-value = 0.002, ß = -0.407, p-value = 0.01). CONCLUSIONS: A reduced volume of the mediodorsal and anteroventral thalamus, overlapping structures between the anxiety related circuits, are associated with more severe PD-related anxiety and may explain its high prevalence in the disease.