A myelinated nerve has a myelin sheath. It is made that way. An unmyelinated nerve is a small fiber nerve. Multiple Sclerosis, for example is a disease where the myelin sheath deteriorates. For a myelinated nerve to function properly, it needs the myelin sheath, that is what helps conduct electricity. Once demyelinated, they seldom ever myelinate again, I won't say never. Some small nerve fibers are myelinated, but most are not....they are simply unmyelinated fibers...never had myelin, never will.


Small fiber nerves innervate absolutely every millimeter of your body. Your autonomic nervous system is predominantly small fiber nerves, and your sensory nervous system is a lot of small fibers too.

When sensory nerves are damaged, they send inappropriate signals to the brain to interpret. They are broken and therefore send the wrong message...such as, pain, when you are not hurt, or numbness or nothing when you are badly hurt, or tingling just for the hell of it.

They also may make your blood vessels contract or dilate inappropriately to heat or cold. They may make you not sense heat or cold properly.

The other thing about small fibers is they control heart rate. If you need to have more blood to the brain they are supposed to increase your pulse. If they are damaged, they don't do this properly. The small fibers also control blood vessels as I said, and generally this works in tandem with your heart rate....special receptors sense your position or exertion level, or heart rate and increase or decrease your pulse accordingly. For example, fluid drops to your feet when you stand and in a properly functioning human, your veins construct and employ strategies to return blood up against gravity. For some one who has small fibers that do not function properly, they can have lethal arrhythmias, or fatal drops in blood pressure. Management of blood pressure and heart rate become very serious issues for people afflicted with this kind of neuropathy. Some people get high blood pressure when they lay down and when they get up, it drops precipitously and they feel like passing out. It has to be managed with medications and fluids. Often times, these individuals get excruciating headaches, as they do not get enough blood to the head and neck. Often times they feel like they will pass out. It feels like the gravity on Jupiter would feel.

They almost always have sensory neuropathy as well.

Often times, these people have no or little innervation of sweat glands, or they don't feel heat and henceforth do not sweat or their blood vessels do not dilate to disappate heat.

Small fibers innervate your stomach. Damaged fibers-no stomach movement, food sits in there for hours---also transit time in your intestine is delayed. The result can be horrible constipation and vomitting, and of course the ever present sensation that one is going to puke. Some people can only eat frequent, small liquid meals. Because their stomach feels full, they don't like to drink enough, and they can overheat, or get hypovolemia.

As of yet, small fibers have not been known to regenerate. I think, and this is my personal opinion, that exercising them helps get blood flow to them, however, this is not going to stop the process of degeneration as far as I know. Some people do not know why they have this condition despite all testing. Good nutrition is probably helpful too. It probably is good to remove any offending possibility if you can. If I had any inkling of what causes my PN, I would control it. I don't know, so I can't do much to stop it. So I do what doctors advise healthy people to do, exercise and eat right.

It is theorized that barometric pressure can cause pain, but they don't know why. People with pain problems do best in climates with fewer weather fronts and dryer, sunnier weather.