Guillain-Barré syndrome pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, MBBS [2]
Overview
Guillain-Barré syndrome (GBS) is an acute, autoimmune, polyradiculoneuropathy affecting the peripheral nervous system, usually triggered by an acute infectious process. It is included in the wider group of peripheral neuropathies. There are several types of GBS, but unless otherwise stated, GBS refers to the most common form, acute inflammatory demyelinating polyneuropathy (AIDP). It is frequently severe and usually exhibits as an ascending paralysis noted by weakness in the legs that spreads to the upper limbs and the face along with complete loss of deep tendon reflexes. With prompt treatment of plasmapheresis followed by immunoglobulins and supportive care, the majority of patients will regain full functional capacity. However, death may occur if severe pulmonary complications and dysautonomia are present.
Pathophysiology
- GBS is often associated with an antecedent infection with agents such as Campylobacter jejuni or exposure to some vacines.
- These causative agents have certain lipopolysaccharides antigens in their capsules that are similar to gangliosides and glycolipids, such as GM1 and GD1b found in myelin tissues of the peripheral nerve.
- The immune responses directed against these bacterial capsular lipopolysaccharides also targets the similar GM1 ganglioside which are complex glycosphingolipids present in large quantities on human nerve tissues, especially in the nodes of Ranvier. An example is the GM1 ganglioside, which can be affected in as many as 20-50% of cases, especially in those preceded by Campylobacter jejuni infections. Another example is the GQ1b ganglioside, which is the target in the Miller Fisher syndrome variant.
- This type of immune response that are primarily for foreign antigens (such as infectious agents or vaccines) but are mis-targeted to host nerve tissues instead are called antigenic mimicry or molecular mimicry.
- Cellular and humoral immune mechanisms play an important role in the development of disease. Pathologic findings in GBS include lymphocytic infiltration of peripheral nerves, followed by macrophage-mediated, multifocal attack of myelin.
- The end result of such autoimmune attack on the peripheral nerves is inflammation of myelin and conduction block, leading to a muscle paralysis that may be accompanied by sensory or autonomic disturbances.
- However, in mild cases, axonal function remains intact and recovery can be rapid if remyelination occurs.
- In severe cases, such as in the AMAN or AMSAN variants, axonal degeneration occurs, and recovery depends on axonal regeneration.
- Recovery becomes much slower, and there is a greater degree of residual damage. Recent studies on the disease have demonstrated that approximately 80% of the patients have myelin loss, whereas, in the remaining 20%, the pathologic hallmark of the disease is indeed axon loss.
- Loss of myelin and axons result in defects in the propagation of electrical nerve impulses, with eventual absence or profound delay in conduction, causing flaccid paralysis.