Severe axonal degeneration in acute Guillain-Barré syndrome: evidence of two different mechanisms?

Pathogenesis of axonal Guillain-Barré syndrome: hypothesis

Pathologic studies of acute motor axonal neuropathy show strong evidence of the presence of primary axonal Guillain-Barré syndrome (GBS). The pathogenesis of axonal GBS is speculated to be as follows: (1) Infection by an organism induces the high production of a cross-reactive antibody between an infectious agent and the motor nerve axon in patients with a particular immunogenetic background. (2) The antineural antibody binds to the motor nerve terminals, thereby inhibiting motoneuron excitability and causing muscular weakness. (3) Binding of the antineural antibody, or subsequent functional impairment of the motoneurons, causes the motor axon to degenerate from the terminals. (4) In severe cases, extensive axonal loss and central chromatolysis of the motoneurons occur. These inhibit recovery and lead to a poor functional prognosis.

Axonal Guillain-Barré syndrome

The issue of "axonal" Guillain-Barré syndrome (GBS) remains controversial. Supportive evidence comes from pathological examination of peripheral nerves in 4 extreme cases of GBS 17-29 days after onset which showed severe axonal degeneration without inflammatory-demyelination. It has been suggested that inflammatory-demyelination may have been missed. This is difficult to disprove but it seems unlikely, given the known correlation between the severity of axonal degeneration and inflammation/demyelination in the experimental model of GBS, experimental allergic neuritis (EAN). Electrically inexcitable nerves in GBS may reflect axonal degeneration, terminal demyelination or both. This finding proved to be a sign of poor prognosis in 19 of 27 (70%) patients, although a good outcome occurred in some cases.