When pins and needles can work on your nerves

That tingling feeling is usually harmless, but it’s best not to ignore the signs, writes

EVERYONE has experienced it: that tingling, prickling feeling you get in your limbs when you’ve been sitting or lying in one position for too long. Medical people call it parathesia, but to the rest of us it’s “pins and needles”. And here’s how it works.

Our bodies contain miles of nerves and blood vessels. Most people know that nerves carry electrical impulses to and from the brain, and blood carries oxygen and nutrients to our organs.

What people are less familiar with is the fact that nerves also need blood vessels and blood vessels need nerves.

Nerves are made of living cells and there are special blood vessels called vasa nervosum that deliver oxygen and other nutrients to them. Blood vessels also need nerves to ensure the body is kept at the right temperature and the right amount of blood gets to where it needs to be. Nerves help change the diameter of blood vessels. Compression of nerves or the blood vessels interferes with the ability of the nerves to transmit impulses back to the brain, so the brain interprets the lack of signals as pins and needles.

Long-term compression can progress to more permanent nerve damage or dysfunction.

Some forms of pins and needles are caused by occupation or lifestyle, such as carpal tunnel syndrome (CTS), which occurs when the median nerve, which passes through the carpal tunnel, becomes compressed by inflamed tendons.

People who use equipment that vibrates, such as pneumatic drills or orbital sanders, are at increased risk of CTS, as are people who use computer keyboards for long periods of time.

These kinds of activities cause stresses that can pinch the median nerve.

While CTS is usually caused by hard work, Saturday night palsy, as the name suggests, usually results from letting your hair down.

People get Saturday night palsy when they “fall asleep” with their arm hanging over something, like a chair, bar stool or edge of the bed. Initial pressure causes pins and needles, but this can progress quickly to longer-term damage.

Saturday night palsy affects the radial nerve in the arm. One study showed over 70% of reported injuries involved alcohol in some form, and over 75% of people with the condition compressed the nerve for over two hours, resulting in recovery that took weeks.

Clinical evidence shows that this type of injury is on the rise.

The same nerve can be injured in another type of palsy. This one is called “honeymoon palsy”. It happens when your partner lays or sleeps on your arm or leg for so long that it causes palsy.

“Tingling thigh syndrome” and “tight jean syndrome” are terms for a medical condition known as meralgia paresthetica. It is experienced as pins and needles in the outer part of the thigh. These result from compression of the lateral cutaneous nerve of the thigh.

There are many causes like trousers that are too tight; carrying a wallet, keys or phones in pockets; as well as impact to the thigh during sports.

While many of the examples listed above are temporary, there are some instances where pins and needles shouldn’t be ignored. For example, tingling in the lips can indicate a food allergy or a stroke. Tingling in the hands and feet can also indicate mineral or vitamin deficiency. So pins and needles is a way of telling you that something is wrong, although most of the time the cause is benign.

Adam Taylor is director of the Clinical Anatomy Learning Centre and Senior Lecturer, Lancaster University.

| The Conversation