Poliomyelitis

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Poliomyelitis is an infectious disease that used to be the most common cause of paralysis in young people. For this reason, it was known as infantile paralysis.

The processes that bring about movement of the voluntary muscles of the body start on the surface of the brain in an area called the motor cortex. From this region, nerve fibres run down in bundles through the substance of the brain into the brain stem and spinal cord.

At all levels of the cord, these fibres connect up with other nerve cells lying at the front of the spinal cord on either side of the mid-line. These are called the anterior horn cells because, in a cross-section of the cord, the white matter (nerve cell bodies) is in the form of an expanded H that appears to have front and back â€˜hornsâ€™, also known as poles. These motor nerve cell bodies are in the front pole of the white matter. Anterior means front. This is in contrast to the sensory nerves that enter at the rear pole (posterior pole).

Myelitis means an inflammation of the spinal cord. In the case of this disease, it is an inflammation of the anterior pole cells of the spinal cord. The anterior pole cell collections, running all the way down the front of the cord, are the cell bodies of the spinal nerve that run out of the cord to all the voluntary muscles of the body.

Polio was once a common cause of death, but widespread vaccination has greatly reduced it. Better hygiene and sanitation have helped, but vaccination is the most important reason why this disease is now so rare in the UK. There now seems a real prospect that, like smallpox, polio may be eradicated entirely from the world.

The viruses that cause this disease have a particular tendency to attack the anterior pole cells, causing the column of tissue they form to become inflamed. For these reasons, the full name of the disease is acute anterior poliomyelitis. The name is usually abbreviated to poliomyelitis, or more commonly, polio.

Post-Polio Syndrome (PPS) is a condition that affects around 25% of polio survivors anywhere from 20 to 40 years after their recovery from polio and after a period of recovery of at least 10 years. It involves the death of individual nerve endings. Symptoms of PPS include fatigue, slowly progressive muscle weakness, muscle and joint pain, and muscular atrophy. The severity of PPS depends upon how seriously the survivors were affected by the first polio attack. No certain cause for post-polio syndrome has been found.