It's a sensation of tingling, burning, prickling or numbness, most often in your arms, hands, legs or feet.
Usually, it happens after you’ve held a position too long – say, sitting cross-legged – that puts pressure on a nerve or limits blood flow.
The affected body part has, in popular parlance, “fallen asleep”.
The medical term is paraesthesia, but is it a cause for concern?
“It’s something we’re all familiar with, and in itself, harmless,” says neurologist Dr Claudia Sommer.
When you change position and stretch the body part, it might be painful or prickle sharply for a moment.
“But then it quickly goes away and the problem is solved,” says Dr Sommer, a senior neurology professor at Wurzburg University Hospital in Germany.
Older people – starting from about age 50 – experience transient paraesthesia more often.
The reason for this being that their connective tissue loses firmness.
“If you rest your arm on the edge of a table, for instance, nerves are pinched more easily because tissue provides less resistance,” she explains.
Harmless pinched nerves or restricted blood flow aren’t the only causes of paraesthesia, however.
Time to see the doctor
When can it be a sign of a medical condition?
“The numbness shouldn’t last too long,” says Prof Sommer.
“If you’re healthy, you shake it off and everything’s fine again.
“But if it persists, you should find out why”, especially if there’s no apparent reason for it.
The first place to turn to is your general practitioner (GP).
“If the symptoms are in your arms or legs, it could be a neurological problem,” says Münster University Hospital Clinic for Vascular and Endovascular Surgery head and German Society for Vascular Surgery and Vascular Medicine (DGG) vice-president Prof Dr Alexander Oberhuber.
Three possibilities, he points out, are a herniated (“slipped”) spinal disc, carpal tunnel syndrome or ulnar nerve entrapment (aka handlebar palsy), among other things.
A herniated, or prolapsed, disc is when the rubbery cushion of tissue between the bones in your spine bulges outwards, often irritating nearby nerves.
If cervical (neck) vertebrae are affected, numbness or tingling may be felt in your hands and/or fingers.
In lumbar (back) disc slips, symptoms are typically felt in your buttocks and/or legs.
The carpal tunnel is a narrow passageway on the palm side of your wrist, bound by the carpal bones and traversed by nine flexor tendons and the median nerve.
This nerve controls movement and sensation in your forearm, wrist, hand, thumb and fingers, except for your little finger.
If the median nerve is compressed, its signals are blocked, which can result in pain, numbness and tingling in your thumb and fingers.
A frequent cause is overuse of the wrist, for instance while working at a computer.
“At the first sign of symptoms, you should take preventative action by switching to a more ergonomic keyboard or mouse,” advises Prof Sommer.
ALSO READ: Are you having problems with your wrists?
Ulnar nerve entrapment is a condition most common among racing cyclists.
The ulnar nerve passes through your elbow and wrist.
Entrapment is when the nerve is irritated or compressed – usually at the elbow – often resulting in numbness, tingling and pain in the ring and little fingers.
It can be caused, for example, by gripping a bicycle handlebar in a certain position, especially on long rides or rough terrain.
If left untreated, it can lead to lasting damage.
Ways to prevent or mitigate the condition include correctly adjusting the handlebar, wearing padded cycling gloves to absorb vibration and taking regular breaks.
ALSO READ: How to prevent injuries while cycling
A dangerous circulatory disorder – due to thrombosis or atherosclerosis (hardening of the arteries), for example – can also be behind tingling sensations or numbness.
This calls for prompt action, Prof Oberhuber says, “because your body is crying out for help – muscles are insufficiently supplied with blood, and nerves are gradually being damaged”.
It’s important, he adds, that doctors correctly interpret the signals.
Prevention tactics
The risk of such disorders can be lowered, and lifestyle plays a key role.
“It’s very important to quit smoking,” Prof Oberhuber says.
“And that doesn’t mean just cutting down on the number of cigarettes you smoke.
“Quit means quit.”
Getting plenty of exercise and eating healthily are important too, he says.
Ideally, this principally means reducing the amount of red meat you consume and focusing on a Mediterranean diet, which emphasises legumes, vegetables, fruit – mainly berries – and nuts.
While in some cases, paraesthesia can arise from an inherited condition, “the risk reduction is relatively clear”, Prof Oberhuber says.
He advises people with pre-existing conditions to make sure their blood pressure is well controlled and elevated blood fat levels are treated with medications.
What about tight hair ties on your wrist? Can they seriously restrict blood flow or pinch nerves?
“I can’t imagine they cause any harm,” says Prof Sommer.
“The hair tie would have to be so tight that wearing it hurts”, which simple common sense should prevent.
Nor is wearing tight clothing inherently harmful to health. – By Katja Sponholz/dpa
