Impulse Control Disorder Among Parkinson's Disease Patients; Clinical and Neurophysiological Study

Parkinson disease (PD), is a multisystem disease with motor and non-motor (NM) deficits. Dementia and mild forms of cognitive impairment as well as neuropsychiatric symptoms (i.e., impulse control disorders) are frequent and disabling non-motor symptoms of Parkinson's disease (PD). According to the fifth edition of the American Psychiatric Association's Diagnostic and Statistical Manual (DSM-5), impulse control disorders are defined as "disruptive, impulse-control, while conduct disorders include conditions involving problems in the self-control of emotions and behaviors".

Many studies have highlighted potential risk factors for these behaviors, including the fact that that ICDs are associated with younger age, male sex and younger age at disease onset. Also these behaviors have been consistently linked to the use of dopaminergic medications used to treat Parkinson's disease motor symptoms (dopamine agonists, levodopa, and other agents) and less consistently to neuro-modulation techniques such as deep brain stimulation (DBS).

Up to 14-17% of patients with Parkinson's disease display a set of impulsive-compulsive spectrum disorders during the course of illness. Once uncontrolled behaviors develop, either patients fail understand or recognize the severity of their actions or hide them in shame with devastating social and financial results for themselves and their families.

Previous neuropsychological studies have also demonstrated that impulse control disorders in Parkinson's disease are associated with an altered cognitive profile, characterized by impaired cognitive flexibility and planning capability as well as by more inappropriate behavior and poor feedback processes. Also, Cognitive impairment and dementia in particular are associated with adverse outcomes, including gait impairment and falls, greater disability and caregiver burden, higher economic costs, and increased mortality.

Motor deficits have been repeatedly associated with changes in the activity of the motor cortex, in patients with Parkinson's disease. A key regulator of cortical motor output is the balance between excitation and inhibition, which can be assessed in humans with transcranial magnetic stimulation (TMS) techniques.