SPRINGFIELD, Ill. — Farmers and farm laborers work on their feet, so stability and mobility is an important issue. Neuropathy can wreak havoc with farmer’s ability to operate machinery and complete their farm tasks, when it causes loss of balance or limits movement.
It is important to know what neuropathy is and what causes it. Dr. James M. Gilchrist, Neurology Department chair at Southern Illinois University School of Medicine, explained "pathy" means something has gone wrong. "Neuro" relates to nerves; put them together and the big picture is that something has gone wrong with the nerves or nervous system.
Neuropathy is not identified in a single disease, but is often a consequence of an underlying medical condition, such as diabetes. "Everything the nerves need to survive is made in the cell body in the spinal cord: proteins, molecules et cetera. These have to go from the spinal cord to the nerve, and that is called axoplasmic transport," Gilchrist explained.
When something interrupts that transport, neuropathy occurs. When all is well, the messages and the needed substances are transported to the rest of the body and messages successfully back to the brain.
He said there are different types of nerve fibers that carry the messages. The first, unmelinated peripheral nerves, are like "bare copper wire" without any covering. These nerves make up 90 percent of the peripheral nerve system. "They react to touch, temperature and pain," he said.
Peripheral nerve fibers include the motor nerve fibers that work the muscles and the sensory nerve fibers that affect the skin. These fibers have insulation, called myelin, which allows them to send messages faster. Peripheral neuropathy does not include nerve damage in the central nervous system.
A wide array of symptoms can occur when these nerves are damaged; this failure is called Peripheral Neuropathy. According to the National Institute of Neurological Disorders and Strokes (NINDS), "Some people may experience temporary numbness, tingling and pricking sensations (paresthesia), sensitivity to touch or muscle weakness. Others may suffer more extreme symptoms, including burning pain (especially at night), muscle wasting, paralysis or organ or gland dysfunction.
"People may become unable to digest food easily, maintain safe levels of blood pressure, sweat normally or experience normal sexual function. In the most extreme cases, breathing may become difficult or organ failure may occur."
Messages sent through the unmyelinated peripheral fibers move slower than the myelin-sheathed fibers that carry messages at a rapid pace to the extremities and throughout the body.
"Movement must be instantaneous," Gilchrist said, referring to the rapid pass of messages from brain to spinal cord and back again for the myelin-insulated motor nerve fibers. The myelin is made up of protein and fatty substances.
When farming and using machinery, especially, that instantaneous response is crucial. The myelin-covered nerve fibers sense reflexes and joint position sense. Gilchrist explained, "This is the ability to touch your nose when your eyes are closed. Joint positioning is an important thing."
The myelin-covered fibers make up 10 percent of the system and determine joint positioning and reflexes. Gilchrist said failure of these melinated fibers is Demyelinating Neuropathy, and this can cause loss of the ability to coordinate complex movements like walking from the truck to the combine, fastening buttons and maintaining balance when eyes are shut.
Another type of neuropathy that affects the motor nerve fibers is axonal neuropathy, which involves degeneration of the entire axon, rather than only the myelin sheath.
Gilchrist said, "This disease affects the nerve fibers themselves. Most neuropathies (including axonal neuropathy) affect the longest nerve fibers first in the feet and hands; normally first in the feet."
One of the underlying conditions of neuropathy is diabetes. "Sixty percent of diabetics will get neuropathy. For the vast majority, it is mild."
Most diabetics have distal (furthest away thus in the extremities, like the feet) sensory neuropathy that doesn’t advance much. Around 15 percent of diabetics will have a more painful component.
While not common in the United States, leprosy is a common cause of neuropathy in other countries. "Other causes of neuropathy are toxins, alcohol, chemotherapy, antibiotics and inflammation," Gilchrist said. "There is some greater risk of toxic neuropathy due to pesticides/herbicides amongst farmers, though many of the offending agents have been removed from market or are clearly labeled as such."
Inflammation of the blood vessels, kidney disease and other diseases like Lyme disease, Charcot-Marie-Tooth and Guillain Barre Syndrome, can play a part in neuropathy.
Then there about 30 percent of cases, Gilchrist said, that a cause is not found.
"We can speculate that it may be hereditary or that there is a mild inflammation," he said. As for treatment, "Depending on the cause, maybe we can stop it – but first we must find the cause."
When a patient comes with symptoms often described as a tingling or burning sensation or similar to what it would be like wearing a thin stocking or glove, the first thing he does is to run tests to diagnose the cause. An individual’s particular symptoms depend on the type of neuropathy and the type of nerves affected.
After a diagnosis, Gilchrist said he will discuss the options, which vary greatly.
"The nerves are often an innocent bystander of other diseases," he explained.
In the case of diabetes, managing the disease as much as possible and not smoking or drinking is the best way to reduce the chance of neuropathic progression. "Diabetics have bad blood vessels and can get deformities of the toes and get drop feet. Podiatrists spend a lot of time working with diabetics," Gilchrist said.
