Abstract
Background Miller Fisher syndrome (MFS) is an uncommon variant of Guillain-Barré syndrome (GBS) characterised by ophthalmoplegia, ataxia, and depressed or absent muscle stretch reflexes. GQ1b ganglioside is a cell surface component present in the third, fourth, and sixth cranial nerves. IgG antibodies against GQ1b can develop following some infections due to molecular mimicry, and are an important mediator of the ophthalmoplegia seen in MFS.
Cases Case 1 was a 35 year old woman presenting at 9 weeks gestation with acute diplopia, having tested positive on respiratory NAAT to COVID-19 the preceding day. Initial examination revealed an isolated near complete right abducens palsy, but over two days she developed a bilateral complex ophthalmoplegia with non-fatiguable ptosis, bilateral ataxia, and diffusely depressed or absent muscle stretch reflexes. Case two was a 42 year old man presenting with acute diplopia, having tested positive on respiratory NAAT to COVID-19 two days prior. Initial examination demonstrated right eye exophora and hypophoria (‘down and out’) consistent with a pupil-sparing partial oculomotor nerve palsy, and a fatiguable right eyelid ptosis. Upper limb muscle stretch reflexes were depressed, but there was no ataxia. Both patients tested negative for GQ1b, AChR and MuSK antibodies and received intravenous immunoglobulin, making prompt and complete recoveries.
Conclusions We systematically reviewed similar reported cases (37 total), and anti-GQ1b antibodies were only detected in 28% of 25 cases tested, compared to 83–85% in typical MFS. It is proposed that COVID-19-associated MFS may result from direct viral neurotropism, rather than being mediated by anti-ganglioside antibodies.
