Bickerstaff brainstem encephalitis-Miller-Fisher syndrome (BBE-MFS) overlap with negative anti-GQ1b serology

Bickerstaff brainstem encephalitis (BBE) and Miller-Fisher syndrome (MFS) are rare post-infectious neurological syndromes, usually involving 'anti-GQ1b ganglioside' antibodies. Both syndromes present with ophthalmoplegia and ataxia. However, BBE is differentiated by altered consciousness or pyramidal signs (central nervous system involvement), while MFS has areflexia (peripheral nervous system involvement). Here, we discuss a case of an elderly woman, who, after an initial episode of upper respiratory tract infection, developed bilateral ophthalmoplegia, facial and bulbar palsy, ataxia, depressed consciousness and areflexia. She was diagnosed clinically as a case of BBE-MFS overlap. However, serology was negative for anti-GQ1b antibodies, and brain imaging and cerebrospinal fluid (CSF) analysis were normal. Despite initial clinical deterioration and the need for intubation, she was treated successfully with intravenous immunoglobulin and eventually recovered. This case demonstrates that BBE and MFS can overlap and that early clinical diagnosis becomes essential even if anti-ganglioside antibodies, CSF and imaging studies are negative.