COVID-19 and the peripheral nervous system. A 2-year review from the pandemic to the vaccine era

Increasing literature has linked COVID-19 to peripheral nervous system (PNS) diseases. In addition, as we move from the pandemic to the vaccination era, literature interest is shifting towards the potential association between COVID-19 vaccines and PNS manifestations. We reviewed published literature on COVID-19, COVID-19 vaccines and PNS manifestations between 1 January 2020 and 1 December 2021. For Guillain-Barré syndrome (GBS), isolated cranial neuropathy (ICN) and myositis associated with COVID-19, the demographic, clinical, laboratory, electrophysiological and imaging features were included in a narrative synthesis. We identified 169 studies on COVID-19-associated complications, including 63 papers (92 patients) on GBS, 29 papers (37 patients) on ICN and 11 papers (18 patients) on myositis. Additional clinical phenotypes included chronic inflammatory demyelinating polyneuropathy, vasculitic neuropathies, neuralgic amyotrophy, critical care-related complications, and myasthenia gravis. PNS complications secondary to COVID-19 vaccines have been reported during randomized clinical trials, in real-world case reports, and during large-scale surveillance programs. These mainly include cases of GBS, Bell's palsy, and cases of neuralgic amyotrophy. Based on our extensive review of the literature, any conclusion about a pathophysiological correlation between COVID-19 and PNS disorders remains premature, and solely supported by their temporal association, while epidemiological and pathological data are insufficient. The occurrence of PNS complications after COVID-19 vaccines seems limited to a possible higher risk of facial nerve palsy and GBS, to a degree that widespread access to the ongoing vaccination campaign should not be discouraged, while awaiting for more definitive data from large-scale surveillance studies.