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Porphyria Educational Services

Physiology & Anatomy of Peripheral Neuropathy

What does peripheral neuropathy [PN] affect?
.It affects the peripheral nerves of the Central Nervous System.

The peripheral nerves include the cranial nerves (with the exception of
the second), the spinal nerve roots, the dorsal root ganglia, the peripheral
nerve trunks and their terminal branches, and the peripheral autonomic
nervous system.

The way they are classified, the motor neurons and their diseases are
considered separately.

Nerves are composed of different types of axons.
Large, myelinated axons include motor axons and the sensory axons
responsible for vibration sense, proprioception and light touch.
Small myelinated axons are composed of autonomic fibers and
sensory axons and are responsible for light touch,
pain and temperature.

Small, unmyelinated axons are also sensory and subserve
pain and temperature.

Neuropathies involving primarily the latter two fiber
types are called small-fiber neuropathies.
In PN the nerves are acutely inflamed.

Damage to sensory nerve fibers may cause numbness and tingling.
There may also be sensations of cold,or pain. Such feelings often
start in the hands and feet and spread toward the body center.
Damage to motor fibers may cause muscle weakness and muscle

The peripheral nerves connect the central nervous system to the sense
organs, muscles, glands, and internal organs.

In a study conducted by Dr. Ann M. Brown, MD, a neurologist researching
victims of Gulf War Syndrome and SSI recipients disabled from chemical
toxicology, it has been found that the higher toxic accumulation in a
person's body fat, and red blood cells, the more likely a PN patient will have with
the aggression of their PN.

All patients with PN would carry an inherited autosomal dominant gene
seem the most likely candidates for this aggreesive PN exacerbation.

Sources: Dr. Ann M.Brown, Nerves and Neurology, June 1996.
Ann Noelle Poncelet, M.D. University of California Medical Center,
San Francisco, 1997.