Adapted from BBC
Everyone has experienced that tingling sensation in the hands. It is commonly called “pins and needles” because it feels like tiny pointy needles. Some describe it as numb, or “falls asleep,” and is uncomfortable to place pressure on it.
The sensation itself is called “paresthesia,” or alternate sensation.
Sensation is transmitted from your body to your brain via nerves, your biological Internet cables. If you place too much pressure on one of them, the signal gets distorted. We call it Neuropathy, ie sick nerves. Once the pressure is relieved, it goes back online soon. If the pressure is not removed within reasonable time, it causes permanent change to the inner structure of the nerve and permanent change to the signal. More severe and long standing pressure can cause permanent loss of signal even. There are several nerves in the arm, and each may be subject to pressure at several spots. For more info, check the Numbness and Tingling page.