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GBS – Guillain Barre Syndrome – definition, incidence, etiology

Definition

Guillain-Barre syndrome (GBS; also known as acute idiopathic demyelinating polyneuropathy) is an acute, rapidly progressing, ascending inflammatory demyelinating polyneuropathy of the peripheral sensory and motor nerves and nerve roots.

Motor, sensory, and autonomic functions may be involved.

The syndrome is characterized by a diffuse inflammation or demyelination (or both) of the ascending or descending peripheral nerves that leads to a viral illness and then paralysis.

Incidence

The incidence of GBS is 1.9 per 100,000 persons, and it affects individuals of both genders and of all ages but is rare in infants. Most commonly, it affects young and middle-aged adults 30 to 50 years of age, and men slightly more than women.

Genetic considerations

Though considered to be an autoimmune disorder there have been reports of GBS running in families. There is evidence that some cases may be caused by mutation in the PMP22 gene.

Related anatomy and physiology

The nervous system consists of vast number of cells called neurons. Each neuron consists of a cell body and its processes, one axon and many dendrites. Neurons are commonly referred to simply as nerve cells. Bundles of axons bound together are called nerves.

Cell body

Cell bodies form grey matter of the nervous system and are found at the periphery of the brain and in the centre of the spinal cord. Groups of cell bodies are called nuclei in the central nervous system and ganglia in the peripheral nervous system.

Axons and dendrites

Axons and dendrites are extensions of cell bodies and form the white matter of the nervous system. Axons are found deep in the brain and in groups, called tracts, at the periphery of the spinal cord. They are referred to as nerves or nerve fibers outside the brain and spinal cord.

Axons

Each nerve cell has only one axon, carrying nerve impulses away from the cell body. They are usually longer than the dendrites sometimes as long as 100cm. The membrane of the axon is called axolemma and it encloses the cytoplasmic extension of the cell body.

Large axons and those of peripheral nerves are surrounded by a myelin sheath. This consists of a series of Schwann cells arranged along the length of the axon. Each one is wrapped around the axon so that it is covered by a number of concentric layers of Schwann cell plasma membrane. Between the layers of the plasma membrane there is a small amount of fatty substance called myelin. The outer layer of Schwann cell plasma membrane is sometimes is called neurilemma. There are tiny areas of exposed axolemma between adjacent Schwann cells, called nodes of Ranveir, which assists the rapid transmission of nerve impulses.

Post gnaglionic fibers and some small fibers are in the central nervous system are non-myelinated.

Dendrites

The dendrites are the many short processes that receive and carry incoming impulses towards cell bodies. They have the same structure as axons but they are usually shorter and branching.

Etiology and risk factors.

    • The exact cause is unknown.
    • Viral or bacterial infection 1 to 3 weeks before the development of symptoms.
    • The most typical site and cause of infections are a lung or intestinal infection caused by Campylobacter jejuni (C. jejuni) or cytomegalovirus (CMV).
    • Infections with Epstein-Barr virus and Mycoplasma pneumoniae are also associated with GBS.
    • Some patients have recent surgical procedures during the 4 weeks before GBS developed.
    • Other diseases that have been linked to the development of GBS are; Lymphoma, Human immunodeficiency virus (HIV) disease, Hodgkin’s disease, Lupus erythematosus, Gastroenteritis.
    • In some cases, GBS develops after immunization for influenza.

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