Have you ever woken up to realise that you can’t feel your arm? At first, you might think it’s some kind of nightmare but it’s actually a recognised thing!
It can be a pretty scary experience waking up and having your arm flop around like that, and in your tired state you’d be forgiven for starting to panic a little bit!
But fear not, after a couple of minutes the feeling always comes back following a bit of pins and needles.
So what is it?
James Dyck, a neurology researcher at the Mayo Clinic in the USA has recently come out with an explanation, revolving around how the body protects itself during sleep.
While you might assume it’s because the way that you sleep is restricting blood flow to the arm, this isn’t the case.
Instead, Dyck blames nerve compression. He said: “The More likely thing is nerve compression – nerves are being pushed on and squashed, and that causes these symptoms.
There are four different types of nerve in the arm:
• Axillary nerve – Lifts the arm at the shoulder
• Musculocutaneous nerve – bends the elbow
• Radial nerve – straightens the arm and lifts the wrist and fingers
• Ulnar nerve – spreads the fingers
Any of these nerves can be compressed either under your own body or that of your partner, which disrupts the flow of information between the limb and your brain.
Why does this cause numbness?
There are two main theories on why nerve compression causes our arms to go all floppy.
The first is that it’s a sign of sleep paralysis. During REM sleep, the brain will send a signal to essentially paralyse the whole body, which stops you from acting out your dreams.
Sometimes, however, you can wake up during this stage, before your limbs do!
The other is that compressing the nerves damages them, and as a natural protection measure your body wakes you up.
According to the University of Rochester Medical Centre in New York: “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 feeling of pins and needles is a good sign.
“It’s is a temporary phase that means nerves are coming back to life.”
Should I be worried?
Fortunately, your arm falling asleep during the night is nothing to worry about and in most cases won’t cause any lasting damage to the nerves.
However, there are a couple of cases where the issue may be a little more serious. The first is if it happens while you’re drunk.
This is called “Saturday night palsy”, and refers to times when the brain is too impaired to wake up the body and protect the nerves from compression.
In addition to a hangover you could wake with a very numb hand or arm which could take a few days to heal.
Some people also suffer from a condition known as hereditary neuropathy with liability to pressure palsies (HNPP).
This condition makes people more susceptible to nerve compression injuries and those who suffer from it can get injured simply from crossing their leg in a certain way for too long.
However, on the whole, waking up with a dead limb isn’t really anything to be worried about, and the fact is that it often seems a lot worse than it is because you’ve just woken up and feel so disorientated!
For more sleepy related news and tips, keep checking back on the Sleepy People blog.