Miller Fisher syndrome following COVID-19 vaccines: A scoping review

Background and Purpose: Miller Fisher syndrome (MFS), a variant of Guillain–Barré Syndrome (GBS), could be underestimated in evaluations of its adverse events (AEs) following COVID-19 vaccination. We aimed to identify and characterize MFS following COVID-19 vaccination. Materials and Methods: Relevant studies reported on during the COVID-19 pandemic were identified in the MEDLINE, Embase, and other databases. Results: Nine cases of MFS following COVID-19 vaccination from various regions were included. Unlike MFS following COVID-19 infection, patients with MFS following COVID-19 vaccination frequently presented with anti-GQ1b antibody positivity (44%, 4/9). Unlike GBS following COVID-19 vaccination, only two of nine (22%) cases of MFS following COVID-19 vaccination had developed after viral-vector-related vaccine administration. Conclusions: Miller Fisher syndrome following COVID-19 vaccination seems to have a different pathophysiology from MFS following COVID-19 infection and GBS following COVID-19 vaccination. This neurological syndrome with a rare incidence and difficulty in diagnosis should be considered an AE of COVID-19 vaccination.