Apathy: a complex symptom specific to the clinical pattern of presentation of Parkinson's disease?

There is currently no consensus on the nosological position of apathy in clinical practice, although many different articles indicate that apathy is a common, behavioral disturbance in the general Parkinson's disease (PD) population, often related to severe motor symptoms, hypothesizing that the dysfunction of the nigrostriatal pathway may play an important role in its pathophysiology. However, not all patients with PD become apathetic, indicating that apathy should not entirely be considered a dopamine-dependent syndrome in PD. The aim of this study was to examine the prevalence and clinical correlates of apathy in a representative community-based sample of patients within 2 variants of the PD: akinetic-rigid type and tremor-dominant type. Specifically, we wanted to investigate whether these 2 variants of PD would present with apathy as a primary behavioral disorder and whether apathy could be associated with different cognitive and behavioral disorders. Apathy is present in both the groups but significantly more evident in the akinetic-rigid group associated with frontal impairment but not related to motor impairment or depression. We discuss the results, starting with anatomical and physiological brain studies.