anti GM1 antibodies pearls

1.  MMN with conduction block presents as asymmetric, painless, slowly progressive weakness especially in distal upper limbs. 
2.  Sensory sparing resembles ALS, however, UMN signs are not seen in MMN
3.   Conduction block outside of normal compression sites differentiates MMN and ALS.  Patients without conducton block occassionally respond to immunotherapy (Neurology 1997 first author JS Katz).
4. High titer IgM anti GM1 are seen in 50-60 percent of patients with MMN, but sensitivity is increased to 80-90 percent by complexing GM1 to secondary antigens co GM1 antibody test (Pestronk, Neurology 1997)
5.  In GBS, anti GM1 antibodies closely correlate with Campylobacter jejuni infection and sometimes correlate with worse neuropathy and outcome
6.  Other antigens coexpressed sometimes in GBS are GD1a, GD1b and GM2; some have argued GM2 correlates with CMV neuropathy but this is not univerally accepted.  GD1a is often seen in AMAN, the Chinese GBS variant (60 %) v. only 4 % of traditional GBS patients