The Influence of Coronavirus Disease-2019 (COVID-19) On Parkinson's Disease: An Updated Systematic Review

Background: COVID-19 has affected global communities with multiple neurological complications in addition to other critical medical issues. COVID-19 binds to the host's angiotensin-converting enzyme 2 (ACE2) receptors, which are expressed in the neurons and glial cells, acting as an entry port to the central nervous system (CNS). ACE2 receptors are abundantly expressed on dopamine neurons, which may worsen the prognosis of motor symptoms in Parkinson's disease (PD). SARS-CoV-2 may lead to an indirect response via immune-mediated cytokine storms and propagate through the CNS leading to damage. In this systematic review, we aim to provide thorough analyses of associations between COVID-19 and neurological outcomes for patients with PD.

Methods: Using PRISMA statement 2020, a systematic review was conducted to isolate confirmed COVID-19 patients and analyze the PD-associated neurological outcomes using the following databases: PubMed, Science Direct, Google Scholar, and Cochrane databases. The following keywords were used "COVID19, SARS-CoV-2, Parkinson's disease, Pandemic, Mortality." A modified Delphi process was employed.

Results: Of the 355 studies located during the initial round of screening, 16 were included in the final synthesis. Of PD patients who tested positive for SARS-CoV-2, worsening motor symptoms and other viral-associated symptoms were reported. These symptoms included bradykinesia, tremors, gait disturbances, delirium and dementia, and severe spasms of arms and legs. Encephalopathy was presented in 2 of the included studies. Increased mortality rates were identified for hospitalized patients due to COVID-19 and PD as compared to other patient groups.

Conclusion: Patients with PD may experience substantial worsening of symptoms due to COVID 19. Given the novelty of neurological-viral associations, clinical studies in the future ought to explore the disease severity and neurological outcomes in COVID-19 positive patients with PD as compared to non-PD patients, in addition to understanding the role of ACE2 in increased vulnerability to contracting the infection and as a treatment modality.