Small fiber neuropathy is really an interesting condition because it consists typically of just burning, numbness, pain of the feet, sometimes the hands later on without necessarily having any abnormalities on your EMG or nerve conduction study. So what I tell patients and actually residents or students who train under us is that a normal nerve conduction study does not exclude a neuropathy. And we will confirm this by doing additional testing, specifically the nervous the the examination at the bedside asking patients about their.
Symptoms, for example, loss of sensation to cool or or hot temperatures, loss of pain sensation and also doing skin biopsies where we look at nerve densities in the skin both from the calf and the thigh as well as doing a special test that looks at sweat function both in your foot in in the legs as well as the feet to gauge the level of small fiber nerve damage. Small fiber neuropathy typically will progress unless the underlying cause is identified and reversed. Diabetes of course being the most common cause is always screened.
For. but once the more common causes are excluded and the focus becomes on excluding any underlying secondary disease process but also controlling pain because if patients’ symptoms of pain are generally controlled they tend to do pretty well and really have no other major functional deficits. I’ve really become interested over the years is how interconnected neurology and rheumatology are and one thing I often do on patients who have unexplained small fiber even autonomic neuropathy is have them see rheumatology or get evaluated for connective.
Causes of Neuropathic Pain
Neuropathic pain differs from other types of pains and in order to start talking about neuropathic pain, it’s important to remember what pain actually is. So, nociceptive pain or pain that we sense usually is nerves transmitting an impulse and letting us know that there is a damage or injury to part of our body. Neuropathic pain is an actual pathology of the nerve itself. Nerve consists of its body, which is the axon, which is the part that usually gets injured and when that axon is injured what happens is abnormal transmission.
Of impulses. it’s important to remember that it’s not nerves communicating an injury elsewhere, but the process in the nerves themselves. Neuropathic pain itself presents differently from other types of pain. So, neuropathic pain is likely to be severe. It is usually sharp. It is electric shocklike sensation that people usually describe. It is lightning or lancinating type of pain that most people talk about when they describe neuropathic type of pain. Accompanying that, it can be a deep burning or, at the same time, it can.
Also present as coldness in the limbs or distribution of that nerve. it also comes, at times, with persistent numbness, tingling, or weakness of the muscles that nerve supplies. Neuropathic pain usually travels along the path of the nerve itself. Because the nerves have different function some nerves are motor nerves, some nerves are sensory nerves if the sensory part of the nerve is affected, it can alter sensation. Now, it can actually decrease sensation in other words, create numbness or it can heighten sensation where.
Normal stimuli are now painful or altered so something that would usually be a normal muscle sensation, such as light touch, can become a painful sensation. There are many causes for neuropathy or neuropathic pain affecting the nerves. Some of those are compression of the nerve. Now, compression of the nerve can occur anywhere along the path of the nerve. It can be as it exits the spine and travels onward, as in radiculopathy or in other words, pain arising from compression of the spinal nerve before it exits the spinal.
Column or it can be peripheral nerve compression. and many of us know what it feels like when we cross our legs and the leg goes numb that is compression of the peripheral nerve and usually that recovers by itself, but if that compression remains for a longer period of time, then that can become not necessarily permanent, but the recovery from that can take months and sometimes even a whole year. Other sources of the neuropathy can be systemic processes, such as diabetes. Diabetes is a microvascular process decreasing the supply.
Of nutrients to tissues as well as nerves and that tends to be what’s called a lengthdependant process, in other words, nerves that are longer tend to be affected first and that’s why people with diabetic neuropathy tend to feel their feet being affected first because the nerves are that much longer, so those nerves tend to be affected first, then the hands follow that because they are the next longest nerves in the body. That being said, any process that can damage tissue can also damage nerve tissue. So, what.
I mean is treatments like chemotherapy there are different chemotherapy agents that can alter different processes that the nerves depend on and some are actually neurotoxic in other words, they are damaging the nerves directly. Now, chemotherapy affecting the nerves can appear at the time of the treatment, but it can also be a delayed presentation of that neuropathy. Also, radiation; a process that radiation causes, in the long run, can come up as postradiation fibrosis. In other words, tissues fibrose and contract and can.