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.

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.

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.

Genetics

[Disease name] is transmitted in [mode of genetic transmission] pattern.

OR

Genes involved in the pathogenesis of [disease name] include:

• [Gene1]
• [Gene2]
• [Gene3]

OR

The development of [disease name] is the result of multiple genetic mutations such as:

• [Mutation 1]
• [Mutation 2]
• [Mutation 3]

Associated Conditions

Conditions associated with [disease name] include:

• [Condition 1]
• [Condition 2]
• [Condition 3]

Gross Pathology

On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Microscopic Pathology

On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].