Arm asleep when you awake? Here's the reason!

[Massageman]

Waking up in the middle of the night to discover one of your arms has lost all feeling can be frightening! At first, the limb is limp and flops around like a useless bag of bones before coming back to life with a potential flood of "pins and needles" sensations.

Most of the time when our arm "falls asleep" there is a simple, temporary reason.

Some people panic, thinking they had done something horribly wrong to their bodies, anxious that they’d never be able to move their arms again. But the feeling in their arms comes back.

This phenomenon is really common, says James Dyck, a neurology researcher with the Mayo Clinic. And it's actually a cool example of how the body can protect itself, even during the paralysis of sleep.

Dyck explained there's a common misconception that pins and needles and numbness are caused by a lack of blood flow to the nerves. "The more likely cause is nerve compression- nerves are being pushed on and squashed- and that is what causes these symptoms.”

You have several nerves in your arm, each serving a vital function. The axillary nerve stimulates the muscles that lift the arm at the shoulder. The musculocutaneous nerve serves the muscles that bend the elbow. The radial nerve triggers the muscles that straighten out the arm and lift your wrist and fingers. Finally, the ulnar nerve stimulates the muscles that spread your fingers.

The effect of compressing any of these nerves during sleep- when you sleep on top of your arm or pin it underneath your bunkmate- is like stepping on a garden hose. Just as the flow of water is slowed or stopped in the hose, the information that flows from your extremities back to your brain is temporarily disrupted.

Localized arm numbness or "pins and needles" upon awakening generally passes within a few minutes.

So why does it feel paralyzed upon waking?

Dyck suggests that is is almost always one of two reasons . A. It IS actually, temporarily paralyzed. During REM sleep, the brain sends a signal to cause a body-wide paralysis, and is a natural protection system for our bodies. The purpose of this is to keep you from physically acting out dreams which occur during REM. But if you wake up suddenly during one of these REM phases, you can become conscious and somewhat alert before your fully regain control of your limbs. This is called sleep paralysis, and it can be a frightening situation. You're stuck somewhere in between dreaming and wakefulness, and you can't move! Scary! Argh! B. The nerve compression has led to a temporary paralysis (perhaps because you got stuck in a compressed position during sleep, perhaps with your arm tucked under your head or pillow).

Nerve compression in the arm while sleeping can cause temporary numbness upon awaking.

Compressing nerves can damage them if continued repetitively over a long period. The good thing is that the body will naturally wake up as another protection mechanism cuts in whenever a nerve has been compressed too long. After you wake and relieve the pressure, the nerves will quickly come back online, usually first with a burst of “pins-and-needles” feelings.

"The nerve structures, as they recover, tend to be irritable for a period of time," the University of Rochester Medical Center explains. "That’s because the nerves are firing spontaneously. Most of the time, the feeling of pins and needles is a good sign. It is a temporary phase that means the nerves are coming back to life.” You might consider this similar to your computer, smart phone or tablet being rebooted after being asleep or shut off.

Occasionally, conditions arise that require a bit more concern. One such cause has been dubbed "Saturday night palsy," and occurs when a person faints and falls asleep, falling on their arm and compressing a nerve as they pass out while drunk. The alcohol impairs the body's ability to wake you up and protect your nerves. "If you’re passed out drunk, you can’t move your arm," Dyck says. And when you wake up the next day, you can't extend your wrist and you can’t extend your fingers." That might last longer than a few moments- perhaps even a few days or months- as the nerve has to repair its protective coating, the myelin sheath.

There is also hereditary neuropathy, a genetic condition that makes people more susceptible to nerve compression injuries in general. They might want to be extra careful not to fall asleep on a limb- or even cross their legs- to avoid nerve compression.

But these conditions aside, for most people who wake up to a limp limb, it's just a temporary annoyance. If it becomes a regular occurrence and/or if it happens without the arm being pinned under you, have it checked out by your physician. We want you to be able to type those Questions and Opinions for many years to come!