The Guillain-Barré Syndrome(GBS) is not a single disease entity. It includes several variants: Acute inflammatory demyelinative polyneuropathy (AIDP), acute motor axonal neuropathy (AMAN), and the Miller-Fisher syndrome (MFS). AIDP accounts for 90% of GBS.
It begins with paresthesias in the toes and fingertips, followed by rapidly advancing weakness and areflexia.
Weakness reaches a plateau within four weeks, after which recovery begins. Some cases are fulminant, evolving in one or two days. At the height of their disease, many patients are completely paralyzed and unable to breathe.
Even with modern intensive care, approximately 5% of patients die from respiratory paralysis, cardiac arrest (probably due to autonomic dysfunction), sepsis, and other complications. Ten percent of those who recover have residual weakness.
Though easy to diagnose in its classical form, GBS is often missed because of atypical clinical features which include ophthalmoplegia, ataxia, sensory loss, and dysautonomia. Plasma exchange (presumably removing the offending antibodies) and intravenous immunoglobulin are the treatments of choice.
The two key laboratory abnormalities in GBS are decreased nerve conduction velocity or conduction block and elevated CSF protein with relatively few cells (albuminocytologic dissociation).
Peripheral nerves show perivenular mononuclear cells, demyelination (myelin proteins are the source of elevated CSF protein), and macrophages. Axonal damage, which accounts for the permanent deficits, is variable and may be severe.
The pathology is most severe in spinal roots and plexuses and less pronounced in more distal nerves. In the phase of recovery, the nerve contains thin myelin sheaths, indicating myelin regeneration. AMAN shows axonal damage with little inflammation.
About 20% to 30% of GBS cases are preceded by an infection with Campylobacter Jejuni. An equal number are preceded by Cytomegalovirus (CMV) infection. The rest are preceded by Mycoplasma and other infections, or vaccinations. The bacterial wall of C. jejuni contains GM1 ganglioside.
Anti-ganglioside antibodies, generated in the course of the infection, cross-react with GM1 ganglioside present in the axonal membrane at the nodes of Ranvier and in paranodal myelin. This contact elicits inflammation that damages these structures. Anti-GM1 antibodies are found in the serum of GBS patients. GBS following CMV infections has anti-GM2 antibodies.
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