I have chronic burning pain in my hands from working in a factory where I pull sheets of canvas off a conveyor belt. The doc thinks I've damaged the nerves in my forearms and hands. Tomorrow, I'm having some kind of test called NC-Stat. Can you tell me what the test will be like?
Your symptoms may be coming from compression of nerves in the forearm and hands that are part of the peripheral nervous system (PNS). The peripheral nervous system is made up of all the nerves coming from the spinal cord and going out to the rest of your body. The peripheral nerves can be sensory only, motor only, or mixed (both sensory and motor). Compression of a peripheral nerve can result in a problem called compression neuropathy.
When sensory nerves are affected the result can be symptoms of pain, burning, altered sensation, numbness and tingling, or even complete loss of sensation (paresthesia). Muscle weakness and atrophy are more likely to develop with motor nerve impairment. And a combination of these two sets of symptoms occur with compression of mixed nerves.
Physicians rely on three tools to diagnose nerve injuries: the patient history (your symptoms, what happened, how it happened, when it happened), clinical examination, and electrodiagnostic testing. There are nerve conduction velocity (NCV) tests that measure the speed that messages are sent along the nerve. Another test called compound muscle action potential (CMAP) measures the messages sent along nerves to the muscles. Sensory nerve action potential (SNAP) tests are used to assess nerves that only pick up sensory (not motor) input. There's also the compound nerve action potential (CNAP) used to test nerves that are both sensory and motor nerves. The results of these tests can help determine where the nerve is damaged and how serious the injury might be.
The NC-Stat actually refers to a portable electrodiagnostic device that uses biosensors to detect changes in skin temperature when nerves are stimulated. The NC-Stat helps the physician get a quick idea whether there might be nerve compression before ordering more extensive and expensive nerve tests. The NC-Stat can be performed in the physician's office using surface electrodes instead of needles.
The electrodes look like thin patches. They are placed over the skin along the length of the nerve. The nerve is stimulated to fire through one electrode while the second electrode records the nerve's response. It doesn't measure all nerve function but it can be quite helpful in detecting compression neuropathies.
Minal Tapadia, JD, MA, et al. Compressive Neuropathies of the Upper Extremity: Update on Pathophysiology, Classification, and Electrodiagnostic Findings. In Journal of Hand Surgery. April 2010. Vol. 35-A. No. 4. Pp. 668-677.
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