The peripheral nerve involvement in Parkinson Disease: A multifaceted phenomenon

• The involvement of the peripheral nervous system in the context of Parkinson's Disease is a phenomenon with many facets.
• A peripheral neuropathy (PN) can be observed both in the early stages and advanced disease.
• The late-stage neuropathy is mainly axonal sensitive and is related to the chronic levodopa use.
• The PN detected in early or preclinical stages has intrinsic determinants and especially involves the enteric and olfactory nerves.
• Peripheral involvement could be an early step or, even, the gateway for the neurodegeneration before it spreads to the CNS

In the last decade the possible relationship between Parkinson's disease (PD) and peripheral neuropathy (PN) has received increasing attention.Given that PN is quite common in Parkinson's disease, much controversy has arisen on whether it is part of the neurogenerative process itself - actually one of the possible causes - or a complication of levodopa administration.In this article we will discuss the different hypotheses, as well as our perspective on these open issues.