Histograms showing periods until an improvement of one Hughes grade from onset. Histograms showing periods until an improvement of one Hughes grade from onset. The acute motor axonal neuropathy group (AMAN) (black bars; n = 35) had two subgroups of patients who improved by one grade within four weeks or over a period of months. The acute inflammatory demyelinating polyneuropathy group (AIDP) had a relatively uniform pattern (white bars; n = 22). A Hiraga et al. J Neurol Neurosurg Psychiatry 2005;76:719-722 ©2005 by BMJ Publishing Group Ltd