Guillain-Barre syndrome

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Introduction0:00–0:25

Guillain-Barré syndrome is named after two neurologists- Georges Guillain and Jean Barré, and it’s a demyelinating disease of the peripheral nervous system, which includes all of the neurons that extend beyond the brain and the spinal cord.
Guillain-Barré, or GBS for short, is also called acute inflammatory demyelinating polyneuropathy. Neurons are made up of three main parts.

Physiology0:25–1:04

The dendrites, which are little branches that receive signals from other neurons, the soma or cell body, which has all of the neuron’s main organelles, and the axon, which transmits the signal to the next neuron in the series.
For peripheral nerves, the cell body can either be located in the spinal cord, where it’s called a spinal nerve, or the brain, where it’s called a cranial nerve.
Myelin is the protective sheath that surrounds the axons of the peripheral neurons, allowing them to quickly send electrical impulses.
This myelin is produced by Schwann cells, which are a group of cells that support neurons. In Guillain-Barré syndrome, demyelination happens when the immune system inappropriately attacks and destroys the myelin, which makes communication between neurons break down, ultimately leading to all sorts of sensory, motor, and cognitive problems.

Pathology1:04–3:04

The cause of Guillain- Barré syndrome is unknown, but it’s known to develop after a bacterial infection, like Campylobacter jejuni and Mycoplasma pneumoniae, or a viral infection, like cytomegalovirus and Epstein-Barr virus.
Specifically, some strains of Campylobacter jejuni have a particular kind of oligosaccharides on their membrane, that are identical to gangliosides found on the surface of motor neurons.
So as a result, immune cells mistakenly attack and destroy the gangliosides, damaging the neurons. This is called molecular mimicry, because from the perspective of the immune cells, a host substance is mimicking a foreign protein.
When a normal component of the cells triggers an immune response that component is called an autoantigen. So in Guillain-Barré syndrome, neuronal autoantigens get picked up by antigen presenting cells, like dendritic cells, which present it to the helper T cells.
These helper T cells produce small signalling molecules called cytokines, which activate B-cells and macrophages. Once activated, the B-cells make antibodies that mark the autoantigens, and the macrophages use those antibody markers to bind to and strip the myelin sheath off of the peripheral neurons.
The demyelination occurs in patches along the length of the axon, so it’s called segmental demyelination. Early on in Guillain-Barré syndrome, the Schwann cells make new myelin to cover the neurons, which is called remyelination.
But over time, the Schwann cells just can’t keep up, and there’s irreversible damage. Absence of myelin sheath means that nerve impulses become slow and sluggish.

Symptoms3:04–4:04

Symptoms of Guillain-Barré syndrome are based on the nerves that are affected. Initially there’s a loss of sensation, also called paresthesia, and it particularly affects nerves that convey vibration and touch sensation.
When motor nerves supplying the muscles are affected, there’s initially muscle weakness and an absence of reflexes. First the ankle reflexes are lost and over soon after, the patellar, and arm reflexes are lost as well.
These are considered lower motor neuron signs. The cranial nerves can also be involved, and that can cause symptoms like double vision and difficulty speaking.
In severe cases, nerves supplying the respiratory muscles like the diaphragm can be involved, and that can eventually lead to death.
When autonomic nerves, which regulate various organ functions, are involved, there can be a variety of symptoms like bowel and bladder symptoms like constipation and urinary incontinence or orthostatic hypotension, which is when there’s a decrease in blood pressure when a person stands up.
To help diagnose Guillain-Barré syndrome, a lumbar puncture can be done to obtain cerebrospinal fluid. The cerebrospinal fluid typically shows an albuminocytologic dissociation which means that there’s an increase in protein or albumin levels, without an increase in white blood cells.

Diagnosis4:04–4:39

In addition, nerve conduction tests and electromyographic studies can be done to assess nerve and muscle function, but sometimes these tests can be normal early on in the disease.
In addition, pulmonary function tests can be done to evaluate an individual’s respiratory function. Treatment of Guillain-Barré syndrome is aimed at reducing the symptoms, and involves medications which suppress the immune system like corticosteroids and intravenous immunoglobulins.

Treatment4:39–5:16

In addition, plasmapheresis can be effective as well, which is when the plasma is filtered to remove the troublesome autoantibodies.
Typically, individuals slowly recover over several months, as there’s regrowth of the myelin on peripheral nerves. Finally, in rare cases, individuals have developed Guillain-Barré syndrome soon after getting the flu vaccine.
In those situations, individuals are often advised to avoid the flu vaccine in future years. ##Summary All right, as a quick recap, Guillain-Barré syndrome is an autoimmune demyelinating disorder, where the immune cells attack the gangliosides found on the surface of motor neurons.

Review5:16–5:43

The result is a progressive loss of nerve impulse conduction, which causes loss of sensation and muscle paralysis in the limbs, and can eventually lead to respiratory failure.
Typically, individuals slowly recover over several months, as there’s regrowth of the myelin on peripheral nerves.