Anxiety occurs in approximately 31% of Parkinson’s disease patients, but the underlying mechanisms are not well understood, wrote Nacim Betrouni, MD, of the University of Lille, France, and colleagues. Previous research has shown associations between anxiety severity and increased activity in brain areas of emotion processing, based on MRI and positron emission tomography, but electroencephalography (EEG) has not been widely used, they said.
In a study published in Neurophysiologie Clinique , the researchers compared EEG spectral patterns and functional resting-state networks in Parkinson’s disease patients with and without anxiety disorders. They identified data from 33 PD patients who met criteria for anxiety, and 75 without anxiety. The average age of the patients was 65 years, and the average disease duration was 9.76 years in anxiety patients and 7.83 years in patients without anxiety.
Overall, findings on spectral analysis showed an association between anxiety and changes in the alpha activity in the right frontal cortex, the researchers said. They also found the relative power in the alpha1 frequency band in the right prefrontal cortex was lower in patients with anxiety than without; this finding was significantly associated with avoidance behavior on a subscale of the Parkinson’s Anxiety Scale (PAS_C, P = .035). A trend toward a significant association with episodic anxiety was noted (PAS_B, P = .06), but no significant associations were noted for persistent anxiety or the total scale score.
The imaging also showed an increased connectivity between the insula and the posterior cingulate cortex in several frequency bands in the anxiety patients, the researchers said. “The increased connectivity observed here may be a marker of the maintenance of avoidance behaviors that characterize anxiety in PD,” they noted.
The study findings were limited by several factors including the small and unbalanced proportion of the study population with anxiety, and the consideration of global anxiety only, without distinguishing anxiety subtypes, the researchers noted. Another limitation was the use only of static EEC patterns, without using dynamic patterns, they said.
The study is the first known to use EEG to explore the mechanisms of PD-related anxiety and “the reported results provide new insights, supporting findings of previous studies using other modalities, mainly rs-fMRI, and show that EEG could be a relevant technique to explore these disorders,” the researchers wrote.
However, more research is needed to confirm the findings in patients with a larger panel of anxiety disorders, they concluded.
The study was supported by the Michael J. Fox Foundation. The researchers had no financial conflicts to disclose.