A tingling or numb feeling is a condition called paresthesia. It’s a sign that a nerve is irritated and sending extra signals. Think of that pins and needles feeling as a traffic jam in your nervous system.
When traffic is running smoothly, tiny electrical impulses move along the nerves that run to and from your spine to your arms and legs. These sensations then move up the spinal cord to the brain.
But if constant pressure is placed on a nerve, it causes a roadblock. This prevents the nervous system from carrying the electrical impulses that normally transmit feeling. This often leads to a loss of feeling, or numbness. Sometimes the irritation causes signals when there should be none. This causes a tingling feeling (paresthesia). This can be uncomfortable or painful.
Cause of "pins and needles"
Paresthesia can have many different causes. It's often caused by nerve, spinal cord, or brain irritation or damage. It can be temporary (reversible) or permanent.
While the nerve is squeezed, so are the arteries that feed blood to the nerve. The nerve can't work for long without a steady supply of oxygen and glucose. Anything that gets in the way of the nerve’s ability to send signals or with its blood supply causes a limb to “fall asleep.” For example, people in wheelchairs who sit for long periods of time are more likely to have nerve “traffic jams.”
When the blockage is removed, the nerve cells start waking up as they start getting impulses again. You may start to have an uncomfortable pins and needles feeling. The nervous system tends to become hyperactive as nerves regain normal function.
The nerve structures, as they recover, tend to be irritable for a period of time. That’s because the nerves are firing spontaneously. Most of the time, the pins and needles feeling is a good sign. It's a short-term phase that means nerves are coming back to life.
Paresthesia can be felt in people who have an implanted spinal cord or peripheral nerve stimulator.
When to worry
Most often, pins and needles is just an odd but harmless feeling that we have from time to time. But it can also be more serious. In some cases, a nerve may be seriously injured. Then the nerve may get stuck in a pins and needles stage. And you may have constant pain. A good example is carpal tunnel syndrome or diabetic neuropathy. In these instances, the pins and needles feeling can be a danger signal.
Paresthesia that happens with other symptoms may also mean that there is an underlying condition. People who have this happen very often may have a problem with their nerves. If these symptoms last for a long time or are linked to weakness, talk with your doctor. If paresthesia occurs suddenly and is linked to slurred speech, facial drooping, or weakness, get medical care right away.
