Neurodegeneration and cognition in Parkinson's disease: a review.

Parkinsons Disease (PD) is a neurodegenerative disorder of the dopaminergic neurons in the substantia nigra. Much of the scientific literature on the Parkinson's disease has been focused on the evaluation and management of motor conditions in PD. Much less stress has been laid on evaluating and managing the cognitive disturbances found comorbidly in this condition. Studies have suggested that the cognitive dysfunction observed in PD can range anywhere from individual cognitive deficits to the clinical picture of minimal cognitive impairment to as much as a full-blown dementia like clinical picture. Perhaps because of this poor understanding, the treatments for this comorbidity have not been able to be adequately developed. Right now, only rivastigmine is the approved drug of choice for treatment of dementia associated with PD. In this review we aim at elaborating the individual cognitive deficits associated with PD instead of focusing on full-blown dementia. Our aim at focusing on individual symptoms is important because these symptoms should be evaluated even at the most beginning stages of PD rather than waiting for the patient to report for the symptoms. Therefore, we will aim at elaborating the prevalence, symptomatology and implications for treatment for these cognitive dysfunctions individually. Because covering all the domains of cognitive dysfunctions are not possible here, we will focus on three cognitive impairments which are most commonly observed in the PD patients. These are the (1) Executive function deficits (2) Memory deficits and (3) visuospatial deficits. We will, finally, have an overview of the condition of minimal cognitive deficits observed in PD.