Guillain-Barré syndrome pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Fahimeh Shojaei, M.D.
Overview
Pathophysiology
Physiology
- Soma is the neuronal cell body which is a closed area with cell membrane.
- Dendrites are branched processes which lead the impulse into the neuronal cell body.
- Axons in a single process which lead the impulse away from the neuronal cell body.
- Myelin sheath is the oligodendrocyte membrane which wraps around the axons.
- Myelin sheath is insulated against electrical impulses and is separated by nodes of ranvier which can transfer the electrical impulse.
- This structure leads to fast traveling of electrical impulses.[1]
Pathogenesis
- The exact pathogenesis of Guillain Barre syndrome is not completely understood but in 2/3 of cases there is a history of an infectious disease in the past month.
- The most common pathogens responsible for these antecedent infections are:
- Campylobacter jejuni
- Cytpmegalo virus
- Hemphilus influanza
- It is believed that the main underlying etiology of GBS is an autoimmune reaction.
- The main theory explaining the relation between these infections and GBS is molecular mimicry.
- There are many antigens on the surface of these pathogens which are similar to myelin sheath or axonal proteins.
- Campylobacter jejuni LPS contains antigens resembling GM1 and GQ1b.
- In the serum of GBS patients with campylobacter jejuni as the antecedent infection, we may see antibodies against GM1 and GQ1b which can cause AMAN and Miller Fisher respectively.
- In the serum of GBS patients with CMV as the antecedent infection, we may see antibodies against GM2.
- Haemophilus influenzae have GM1 like structure on its surface and in the serum of patients with haemophilus influenzae related GBS we may see antibodies against GM1.
- although antibody formation and humoral immunity said to be the underlying pathophysiology mechanism, sometimes pathologic findings underscore the importance of circulating antibodies in the pathogenesis of GBS.
- there are 4 types of GBS with different pathological sequences of events:
- AIDP:
- Lymphocytes will infiltrate in peripheral nerves and nerves root of spinal cord.
- Complement components will deposit in the outer surface of schwann cell membrane and starts the process of myelin disruption.
- Macrophages will infiltrate and complete the demyelination.
- AMAN:
- IgG and activated complement attack to the axolemma of motor fibers in ranvier nodes.
- Macrophages will migrate to these nodes and separate the axon from overlying shcwann cells and destroy the axolemma.
- AMSAN:
- Very little lymphocyte infiltration
- direct attack to the axon of motor and sensory neurons.
- Miller Fisher:
- IgG antibody against GQ1b ganglioside which is present in the ocolomotor nerve, cerebellar neurons and dorsal root ganglion cells.
- AIDP:
Genetics
- There is no characteristic genetic association with GBS.
Microscopic Pathology
- On microscopic histopathological analysis:
- AIDP: Lymphocyte and macrophage infiltration, demyelination.
- AMAN: Macrophage infiltration and axolemma disruption in motor fibers.
- AMSAN: Disruption of both motor and sensory fibers. Little lymphocyte infiltration.
- Miller Fisher: Oculomotor nerve demyelination.[2]
References
- ↑ Mattle, Heinrich (2017). Fundamentals of neurology : an illustrated guide. Stuttgart New York: Thieme. ISBN 9783131364524.
- ↑ Phillips MS, Stewart S, Anderson JR (May 1984). "Neuropathological findings in Miller Fisher syndrome". J. Neurol. Neurosurg. Psychiatry. 47 (5): 492–5. PMC 1027825. PMID 6736980.