Cognitive and affective disturbances in patients with Parkinson's disease: Perspectives for classifying of motor/neuropsychiatric subtypes

Parkinson's disease (PD) is a neurological disorder, related to rigidity, bradykinesia, and resting tremors, among other motor symptoms. It is noticed in the increasing frequency of neuropsychiatric disorders, which may be also caused by non-motor symptoms of PD. Treatment of PD is usually based on the classification of motor subtypes; however, it remains unclear whether motor subtypes have differences in the severity of psychiatric symptoms. It determines the importance of discovering possible neuropsychiatric subtypes of PD. We conducted a clinical study, which included group 1 - patients with postural instability and gait disorders dominant (PIGD) subtype, group 2 - patients with tremor dominant (TD) and indeterminate subtypes (non-PIGD), and group 3 - people who did not have CNS damage. We used the Montreal Cognitive Assessment, Russified 20-point version of the Toronto Alexithymia Scale, State-Trait Anxiety Inventory, and Beck Depression Inventory for assessment of the mental status. It was the first time that neuropsychiatric subtypes of PD had been investigated based on the condition of cognition and mood. Cluster analysis gave us the possibility to classify our patients by the following subtype: affective-cognitive PIGD, anxious PIGD, affective-cognitive non-PIGD, and non-PIGD without psychiatric symptoms. This indicates a closed link between psychiatric and motor symptoms, which can be used for the improved treatment of PD.