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Biomedical Engineering

The Biomedical Engineering blog is the place for conversation and discussion about topics related to engineering principles of the medical field. Here, you'll find everything from discussions about emerging medical technologies to advances in medical research. The blog's owner, Chelsey H, is a graduate of Rensselaer Polytechnic Institute (RPI) with a degree in Biomedical Engineering.

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On Pins and Needles

Posted December 04, 2015 12:00 AM by Chelsey H

We've all felt it; the sharp, tingling sensation in our forearm or legs. Most people know this sensation as "pins and needles" or they say their foot has "fallen asleep." Science calls it temporary paresthesia and it occurs when some sort of exterior pressure compresses the nerve and cuts off localized blood flow in a specific part of the body, which messes with that part's ability to send signals to the brain. Image Credit

When your legs are caught against a hard surface, such as from sitting on a chair or crossing your legs, it also puts pressure on the nerves and blood vessels. With those tiny blood vessels impaired, your nerves sense something's not right; they send the tingling sensation as a pain response, which tells you to move the extremity. The peripheral nerves send information back to the brain and spinal cord. When a sensory nerve is pressed it begins to stop working. In time, the affected extremity "falls asleep," which means the sensory messages are blocked.

Removing the pressure often results in return of function. But we all know your leg, arm, or foot keeps hurting even after adjusting your position. This is because your nerves need to restart and return to their normal state. The sensations range from feeling hot to cold to numb. The feeling depends on which nerves are affected. If it's the nerves used for sensing that are compressed, then the area will feel numb. If it's the nerves that tell your muscles to move, then you won't be able to move that part. The nerves may stop firing or fire hyperactively, and the mixed signals are interpreted as burning, prickling, or tingling. Image Credits

Since there is no rule for how quickly the extremity will fall asleep it's important to pay attention to when the sensation starts to occur. For example, if you notice that your leg starts to tingle ten minutes into a movie, start massaging, stretching or readjusting your legs just before that to bring blood to the area

People with poor circulation are more prone to having extremities fall asleep and should avoid sitting cross-legged or readjust frequently to avoid putting pressure on the blood vessels. In general, temporary paresthesia is nothing to worry about. If you have constant pins and needles it could be a sign of chronic paresthesia, which often requires medical attention.

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#1

Re: On Pins and Needles

12/05/2015 12:23 AM

It's not at all clear how this relates to the "pins and needles" sensation I commonly feel when I've been sleeping in a position that reduces (or perhaps stops) blood flow to a hand or foot. The sensation always goes away fairly quickly after I change to a position that allows circulation to that extremity. I don't think the problem is pressure on a nerve, but rather lack of oxygen. ...but I'm definitely NOT an MD!

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Re: On Pins and Needles

12/05/2015 8:59 AM

Lack of oxygen indeed! Red cells in our blood is the one in charge to carry and supply blood to all the tissues/ muscles in the body.. So when blood circulation is interrupted or cutoff, numbness and crampings occurs....

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Re: On Pins and Needles

12/21/2015 4:36 PM

It is more usually due to direct pressure on the nerve. The blood vessels supplying a limb are relatively large, and not so easy to compress, whereas the blood vessels surrounding a nerve are tiny and easy to squash.

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Re: On Pins and Needles

12/21/2015 5:23 PM

I'm very far from being a medical doctor, so I hesitate to argue, but I have difficulty accepting that. In a brief search, I found no reference to blood vessels surrounding nerves or nerve bundles.

Clearly the nerve endings (sensors) need nutrients from the blood to continue to function. I specified oxygen, but the limiting factor(s) may well include other nutrients.

Hoses get stiffer and kink more easily with age, and mine have been aging for 75 years, so I suspect they kink more readily than they used to. I don't remember the tingling when I was young, but then there are a lot of things I don't remember...

Just this morning I awakened with little feeling in my left hand. The elbow was bent in as far as it can go. It was only a matter of seconds after I straightened the arm that the tingling began, and as blood flowed into the hand, I could feel the tingling subside and the feeling return.

Finally, my experience is that pinched nerves are quite painful and the pain is very precisely located. I would not describe the lack of feeling, nor the tingling, as 'quite painful', and it definitely affects a relatively large area: all the digits of that hand.

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Re: On Pins and Needles

12/21/2015 5:48 PM

Well, I retired in 2008, so I'm getting a bit further from medicine myself, but nevertheless human anatomy has not changed in that time. All the tissues, including the peripheral nerves, require a blood supply. If you wish you may conduct another brief internet search for "blood supply peripheral nerve" or even go for the more technical "vasa nervorum" (vessels of the nerves). As a follow-up, you may be intrigued to discover that blood vessels have their own blood vessels (vasa vasorum).
The numbness in your left hand was caused by the ulnar nerve being stretched around your elbow.

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Re: On Pins and Needles

12/21/2015 7:03 PM

No need for argument as what Mr. phph....stated is true! As long as we live, blood is being circulated all throughout... All living organs in our body, up to its tiniest cells need blood perfusion and be oxygenated to survive and function...

To improve blood perfusion in that problem area, you may want to keep it warm, like having the arm loosely wrapped, sort of having sweatered sleeves when going to sleep! The tiniest blood vessels in our hands do get dilated when warmed up, Resulting to a much improved blood flow and better oxygenation!

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Re: On Pins and Needles

12/05/2015 4:20 PM

Here in the South if you feel a tingly feeling, it could be something much worse...

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Re: On Pins and Needles

12/05/2015 7:13 PM

I've heard they've made it to Maryland

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Re: On Pins and Needles

12/07/2015 6:46 PM

Who was the nut that gave them a ride?

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