Neuropsychiatric and cognitive symptoms and body side of onset of parkinsonism in unmedicated Parkinson's disease patients

Introduction: The onset of motor symptoms is primarily unilateral in the majority of Parkinson's disease (PD) patients. Because of the lateralization of several cognitive and neuropsychiatric functions and the role of impaired dopaminergic transmission on non-motor symptoms in PD, the question raises whether body side of onset of parkinsonian motor symptoms might influence cognitive and/or neuropsychiatric domains in idiopathic PD. Methods: Here we investigated the prevalence and severity of neuropsychiatric and cognitive alterations in a cohort of 84 drug naïve PD patients, divided into two groups according to the body side of onset of motor symptoms (42 left onset PD patients-LPD and 42 right onset PD patients-RPD). Eighty-four age-, sex- and educational level-matched healthy subjects (HC) served as controls. Results: Both LPD and RPD patients had higher prevalence and severity of neuropsychiatric and cognitive symptoms with respect to HC. There were no difference between LPD and RPD as to the pattern or severity of neuropsychiatric and cognitive symptoms. However, significantly higher percentage of LPD patients than RPD deviated more than 1.5 SD from mean values of HC at scales for depression. Conclusions: Our results indicate that in early PD patients side of onset of parkinsonian motor symptoms does not influence non-motor accompanying signs, at least at neuropsychiatric and neuropsychological domains, and suggest that differences reported by previous reports may be secondary to disease progression and/or dopamine replacement therapy.