PURPOSE OF REVIEW: Miller Fisher syndrome is a localized variant of 
Guillain-Barré syndrome, characterized by ophthalmoplegia, areflexia and ataxia. 
Bickerstaff's brainstem encephalitis is a related syndrome in which upper motor 
neurone features accompany the classic triad. Anti-GQ1b antibodies are uniquely 
found in both conditions and are believed to be pathogenic.
RECENT FINDINGS: Infectious illnesses usually precede Miller Fisher syndrome. 
The clearest associations have been described with Haemophilus influenzae and 
Campylobacter jejuni infection. Raised cerebrospinal fluid protein is seen in 
60% of patients, but clinical features and anti-GQ1b antibody testing are 
diagnostically more informative. Experimental studies demonstrating 
complement-dependent neuromuscular block may be relevant to the clinical 
pathophysiology of Miller Fisher syndrome. Recent neurophysiological studies 
suggest abnormal neuromuscular transmission occurs in some cases of Miller 
Fisher syndrome and Guillain-Barré syndrome. Recent mouse models have 
demonstrated that presynaptic neuronal membranes and perisynaptic Schwann cells 
are targets for anti-GQ1b antibody attack. The elimination of antiganglioside 
antibodies from the circulation through specific immunoadsorption therapy has 
the potential to ameliorate the course of Miller Fisher syndrome. This condition 
is typically a benign, self-limiting illness. Both plasmapheresis and 
intravenous immunoglobulin may be employed as treatment, especially in cases of 
Bickerstaff's brainstem encephalitis or those with overlapping Guillain-Barré 
syndrome.
SUMMARY: Anti-GQ1b antibody testing has allowed clinicians to develop a greater 
understanding of the spectrum of Miller Fisher syndromes and to refine clinical 
diagnoses in patients with unusual presentations. Experimental studies strongly 
suggest anti-GQ1b antibodies are pathogenic, which in principle should direct 
treatments towards antibody neutralization or elimination.