tokens: The most common presenting symptoms were concomitant presence of optic neuritis and transverse myelitis in 31.8 % ( p=0.95 ) ; only optic neuritis in 31.4 % ( more common in SA ) , p<0.001 ) ; involvement of the area postrema occurred in 21.5 % and brain stem in 8.3 % , both were more frequent in the South American cases ( p<0.001 ) .