People hear the term “pinched nerve”, as in “pinched nerve in the neck”, but often, don’t know what it really means. Most nerves don’t actually get “pinched”, as you would do with your thumb and forefinger
on a garden hose to increase pressure by direct physical contact with the house. Most nerves that are called “pinched nerves” are getting abnormal or excessive amounts of pressure, usually partial pressures. There is a gradient in the opening for the nerve called a “pressure gradient”, and when some object such as disc material, swollen tissues, etc., start to taking up more space in the hole between the bones, the “intervertebral foramen”, there can be a relative pressure increase. This can also happen if a disc starts to taking up space in the spinal canal. This situation, in which an opening through which a nerve courses, has a decrease in its size or patency, it is called “stenosis”.
Increased pressure on the nerve can cause it to function incorrectly, and depending on whether it is a motor nerve, sensory nerve, or mixed, once there is additional pressure, one can have negative outcomes. A motor nerve that has too much pressure on it can result in decreased strength of an extremity for example, or, if there is sensory function to the nerve, one might feel numbness, or a decreased ability to feel certain stimuli.
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Nerves in general, especially nerve roots, are not getting actually “pinched” as in getting a kink in it, but instead, most of the situations people are describing as a pinched nerve, is actually a situation in which there is a pressure increase (or a partial pressure increase) on the nerve. From experiments in nerve physiology, we know that nerves do not respond well to increase pressure on them, and indeed, even a relatively small increase in pressure can have dramatic effects and in causing nerve pathology.
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