Do you ever wake up in the middle of the night and find one of your arms has lost all feeling and become numb? You’re not alone.

Initially, you will find that the limb is floppy before coming back to life as you begin to feel sensations of pins and needles. When this occurs, you might be inclined to panic or worry as you wait frantically for your mobility to return. This issue is very common, said James Dyck, a neurology researcher with the Mayo Clinic.

There is a common misconception that pins and needles and numbness is a result of a lack of blood flow to the nerves. “The more likely thing is nerve compression–nerves are being pushed on and squashed, and that causes these symptoms,” he said.

First, you must understand that there are several nerves in your arms that each serves a vital function:

  • The axillary nerve lifts the arm at the shoulder.
  • The musculocutaneous nerve bends the elbow.
  • The radial nerve straightens out the arm and lifts your wrist and fingers.
  • The ulnar nerve spreads your fingers.

Although Dyck mentions that the exact physiology is not widely understood, the effect of compressing any of these nerves during your sleep–whether you sleep on top of your arm or pin it underneath your partner­–is like stepping on a garden hose.

Why Does Your Arm Feel Paralyzed Upon Waking?


Dyck suggests the following reasons. First, your arm becomes temporarily paralyzed while you sleep. During REM sleep, the brain sends a signal to cause a body-wide paralysis. This happens to keep you from acting out dreams (which occur during REM). However, if you wake up during one of these phases, you can become conscious without regaining control of your limbs. This is known as sleep paralysis. It can be scary to be stuck somewhere in between dreaming and wakefulness and not being able to move.

Related: 6 Diseases Caused by a Lack of Sleep

Second, nerve compression can lead to a temporary paralysis due to a compressed sleep position during REM. Nerves can become damaged due to compression. The good thing is that the body will naturally wake up as a protective mechanism when a nerve has been compressed for too long. After you wake up and relieve the pressure buildup, the nerves will quickly come back to life, causing the pins and needles feeling.

“The nerve structures, as they recover, tend to be irritable for a period of time,” the University of Rochester Medical Center explained. “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 nerves are coming back to life.”

But rest easy, as falling asleep on your limb is unlikely to cause significant damage to the nerves, said Dyck. However, there are some instances when compressed nerves can become a more significant issue.

One such situation is referred to as “Saturday night palsy,” which occurs when a person falls asleep in a position that compresses a nerve while drunk. While the body usually wakes you up to protect your nerves, the alcohol impairs your body.

“If you’re passed out drunk, you won’t move your arm,” Dyck said. “And when you wake up the next day, you can’t extend your wrist, and you can’t extend your fingers.” This can last longer than a few moments, perhaps even several days or months, as the nerve has to repair its protective coating.

There is also hereditary neuropathy with liability to pressure palsies, which is a genetic condition that makes people more disposed to nerve compression injuries. People who suffer from this condition should avoid falling asleep on a limb or even crossing their legs to prevent nerve compression.

It is important to remember that waking up to a dead limb is merely temporary and “probably takes less time [to recover] than you think it does because you’re freaking out about it,” Dyck said.

Related: 42 Strange Symptoms That Can Indicate a Serious Disease


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