Blinking Rate Comparison Between Patients with Chronic Pain and Parkinson's Disease

Blinking can be spontaneous, voluntary, or reflex. Spontaneous blink rate (SBR) is strictly related to dopamine levels in the central nervous system and is considered a reliable noninvasive biomarker of central dopaminergic activity. Reduced spontaneous blinking rate is a common finding in Parkinson’s disease and other parkinsonian syndromes suggesting involvement of fronto-striatal system and a reduced Dopamine tone. Recent evidence indicates a possible relationship between the central dopaminergic system and pain modulation in both animal and human studies. A subpopulation of dopaminergic neurons within the ventrolateral periaqueductal grey (PAG), which is included in the pain modulatory network, projects to brain regions known to be involved in pain modulation. D1 and D2 receptors are expressed in the PAG and seem to have an antinociception activity. The aim of this study is to investigate changes of SBR in patients with Chronic Pain (CP) compared to normal subjects and PD.