RESUMO
Many patients with variant forms of Guillain-Barré syndrome (vGBS) associated with anti-ganglioside antibodies, including Miller Fisher syndrome (MFS), sometimes exhibit miniature endplate potential (MEPP) frequency increases (MFI, described as alpha-latrotoxin-like effects in a previous report) and the factor to produce this effect is present in their sera. MFI-positive sera increase the frequency of MEPPs, then block neuromuscular transmission at the mouse neuromuscular junction. A connection between this effect at the neuromuscular junction and some vGBS symptoms is suspected. We measured MFI directly at several points during the clinical course of 8 vGBS patients who had various symptoms and courses. Six patients had confirmed MFI and this activity decreased with convalescence. In 3 clinically mild cases, we were able to elicit MFI using normal serum to supply complement after exposure to the patient's serum. The anti-GQ1b/GT1a IgG titer, the extent of ophthalmoplegia and the extent of MFI were significantly correlated. They did not correlate with the severity of limb weakness or the occurrence of respiratory failure. These results support the hypothesis that MFI caused by anti-ganglioside antibodies is the pathogenic mechanism responsible for ophthalmoplegia in vGBS; different mechanisms or antibodies may explain limb weakness and respiratory failure. Furthermore, MFI may be an important indicator of how serum injures the nerve terminals. The symptoms of vGBS may result from multiple pathogenic factors.
