SARS-CoV-2 and the risk of Parkinson's disease: facts and fantasy

In each of these instances, there are fundamental clinical and anatomopathological differences (figure). [...]patients in whom scenarios 1 and 2 apply will present with neurological manifestations generally incompatible with the diagnostic criteria for Parkinson's disease, such as acute onset, myoclonus, cerebellar or pyramidal signs, and scarce or no response to levodopa treatment. [...]this classic example of a respiratory virus associated with damage of the substantia nigra triggered a condition clearly different from Parkinson's disease, both clinically and pathologically. [...]unlike in Parkinson's disease, hyposmia is reversible in the majority of cases with COVID-19, and whether or not it reflects the ability of the virus to reach the nigrostriatal pathway remains speculative as there is no direct connection between the olfactory bulb and the substantia nigra in primates. [...]we could perhaps conclude, on the basis of the limited evidence, that SARS-CoV-2 enters the CNS, but no data support a preferential tropism for the substantia nigra.