Guillain-Barré syndrome (GBS) is an acute inflammatory polyradiculoneuropathy, 
which has various clinical presentations and both axonal and demyelinating 
forms. The original description of "ascending paralysis" encompasses the most 
common varieties: the primary demyelinating form, acute inflammatory 
demyelinating polyneuropathy (AIDP), and some of the axonal forms, acute motor 
axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN). 
However, there are now well-documented acute "monophasic" polyneuropathies that 
have a different clinical phenomenology than that described originally by 
Guillain, Barré, and Strohl: Miller Fisher syndrome, pure sensory 
neuropathy/neuronopathy, pandysautonomia, and oropharyngeal variant. Here the 
authors review both typical GBS (AIDP, AMAN, and AMSAN), and variant syndromes 
with a focus on clinical and diagnostic features, pathologic findings, 
pathogenesis, and treatment.