• “Pins & Needles” in the Arms and Legs

    Call them paresthesias, or simply “pins & needles,” we all have had them and it is usually a result of having your extremity, or some part of it in an unusual position resulting in stress or pressure not normally present. Likely this is due to a “pinching” of a nerve or a localized ischemia from compromised blood flow. Once the “pinch” is released and blood supply provided the nerve(s) begin firing and send a host of delayed signals to the region.

    As far back as the 1940s, Oxford University researchers studied the “pins & needles” effect finding that after three to four minutes of carefully applied limb pressure, subjects felt a very light tingling. After 10 minutes, the limb was judged by the subject as completely numb with virtually no feeling and when the pressure was relieved, the “pins & needles” sensation manifested rapidly.

    But not all paresthesias are innocuous—they can signal more serious conditions, such as direct nerve damage, rewarming after hypothermia, Raynaud’s disease, diabetes, burns, strokes, and overuse of alcohol. As it is nerve related, nerve inflammation, injury, and disease can cause paresthesia.

    There are a variety of presentations of what are classically termed paresthesias. Formication is the sensation of insects crawling across the skin; hitting one’s “funny bone”—hitting the ulnar nerve at that unprotected region in the elbow, causes that electric jolt-like sense down the whole nerve. Tapping/hitting most any nerve can cause a similar sensation, the classic occurring in the aged who experience a jolt down the length of the spinal cord after flexing the neck or back at a weird angle.

    A cold sore can cause a tingling sensation caused by the Herpes virus just as a jalapeño pepper can cause significant (!) tingling on the inside of the mouth. These so called “mouth paresthesias” may also be caused by needle trauma to nerves or vessels during dental injections.

    The study of “pins & needles” may also lead to better understanding of complex chronic pain syndromes as well. So, next time your foot or arm or hand gets a “pins & needles” sensation, consider all that is going on, and know that there is a lot of science that has gone into unraveling its mechanics.

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