Parkinsonism associated with viral infection.

There are several known causes of secondary parkinsonism, the most common being head trauma, stroke, medications, or infections. A growing body of evidence suggests that viral agents may trigger parkinsonian symptoms, but the exact pathological mechanisms are still unknown. In some cases, lesions or inflammatory processes in the basal ganglia or substantia nigra have been found to cause reversible or permanent impairment of the dopaminergic pathway, leading to the occurrence of extrapyramidal symptoms. This chapter reviews current data regarding the viral agents commonly associated with parkinsonism, such as Epstein Barr virus (EBV), hepatitis viruses, human immunodeficiency virus (HIV), herpes viruses, influenza virus, coxsackie virus, and Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). We present possible risk factors, proposed pathophysiology mechanisms, published case reports, common associations, and prognosis in order to offer a concise overview of the viral spectrum involved in parkinsonism.

Impulse control disorders, dopamine dysregulation syndrome and sex dysfunction in Parkinson's disease.

Hypersexuality (HS), characterized by an aberrant, compulsive and inappropriate sexual drive, is an underreported and undermanaged complication of the treatment with dopamine agonists in patients with Parkinson's disease (PD). HS is part of the spectrum of impulse control disorders (ICDs). The failure to control these addictive behaviors is distressing for the patient and it is associated with important consequences. Reports of the prevalence of HS showed different results, due to the lack of standardized diagnostic criteria, but also due to the embarrassment or guilt feelings that patients experience regarding their sexual behaviors. Overall, it is considered that HS may occur in 1.92-22.8% of PD patients and the main risk factors involved could be male sex and genetic susceptibility. The pathophysiology of HS is unknown, but several degenerative mechanisms were proposed, involving dopaminergic, serotoninergic and noradrenergic pathways in cerebral regions responsive for planning and rewarding. There are no standardized tools for the assessment of HS in PD patients; however, several scales and questionnaires were developed with the aim of screening and rating the severity of ICDs, including HS. The management of HS is challenging. Discontinuation or reducing the dopaminergic treatment was effective in some cases, but it might lead to worsening of the motor function. A multidisciplinary approach is mandatory to manage the other associated aspects, such as psychological and social consequences of HS.

Gastro-intestinal dysfunctions in Parkinson's disease (Review).

In patients with Parkinson's disease (PD), gastrointestinal dysfunction occurs from the early stages of the disease and even in the pre-motor phase. This condition can include the entire digestive tract, with symptoms ranging from delays in gastric emptying to dysphagia, constipation and even malnutrition. Excess saliva accumulates in the mouth due to the low frequency of swallowing. Dysphagia develops in about 50% of patients and may be a reflection of both central nervous system and enteric nervous system disorder. Gastroparesis can cause a variety of symptoms, including nausea, and also may be responsible for some of the motor fluctuations observed with levodopa therapy. Intestinal dysfunction in PD may be the result of both delayed colon transit and impaired anorectal muscle coordination. In addition, recent studies have demonstrated the role of Helicobacter pylori infection in the pathogenesis of diseases but also the occurrence of motor fluctuations by affecting the absorption of anti-parkinsonian medication. In this review, the main gastrointestinal dysfunctions associated with PD are presented.