By Eve Clayton, Spectrum Health Beat

Odds are you know the feeling: You wake up from a nap and your arm is asleep. Or your foot’s gone numb.

As you move it around, it starts to prickle and tingle. Gradually it wakes up, and a minute or two later you’re back to normal.

What’s this uncanny sensation all about? Is it normal or something to be concerned about?

The short answer is: It depends.

If it’s fleeting and infrequent

The medical term for this feeling of numbness or tingling is paresthesia, and its cause is the compression of a nerve, according to Paul Twydell, DO, a fellowship-trained neuromuscular medicine specialist with Spectrum Health Medical Group.

Paresthesia typically happens if you lie on a nerve while asleep or hold the same position for too long while sitting—like when you’re driving or reading.

If the feeling goes away quickly, this phenomenon is called transient paresthesia, and it’s typically nothing to worry about.

People will wake up with tingling in their hands and think they have a circulation problem, Dr. Twydell said, but that’s not the case.

“It’s just that a nerve is being compressed in the wrist or elbow. And the reason it happens at night is we often sleep with our wrist or elbow flexed or underneath us, or in a strange position.”

A nerve is a bundle of “wires” surrounded by a layer of insulation called myelin, Dr. Twydell explained. Myelin helps speed the movement of electricity along the nerve.

“When that myelin is compressed, that means the messages aren’t getting through very well,” he said. “A lot of times it’s when the compression is released that (the tingling) happens”—as communication is being restored along the nerve.

The nerves most prone to compression are found in the wrist, elbow, knee and upper arm.

If it’s persistent or abnormal

So when might numbness or tingling be a cause for concern? Dr. Twydell recommends that people talk to their doctor if they experience any of the following:

• Persistent numbness or tingling in the hands. This is often a sign of carpal tunnel syndrome, which is treatable—the sooner the better to avoid severe damage and the need for surgery.
• Tingling in the feet, especially at night. This might be an early sign of a degenerative nerve disease called peripheral neuropathy, which is most often caused by diabetes or heredity. Neuropathy isn’t reversible, but it can sometimes be slowed down, Dr. Twydell said.
• Weakness of a limb in conjunction with numbness. This can be a sign of more severe damage to a nerve.
• Numbness or tingling that ascends up the legs or into the abdomen. This can be a sign of spinal cord inflammation or compression.
• Numbness involving half of the body or face. This can be an indicator of stroke, which requires emergency care. Call 911.

If you have persistent symptoms of numbness or tingling, your doctor may order a test of the nerves called electromyography, or EMG. This nerve study can help pinpoint the source of a problem and help guide treatment.

Carpal tunnel syndrome is the most common problem investigated by Spectrum Health Medical Group Neurology in the EMG lab, Dr. Twydell said.

Tips for good nerve health

Your best bet is to avoid activities that cause prolonged nerve compression, Dr. Twydell said. Change positions frequently. Get up and walk around throughout your workday.

“If nerves are compressed over and over again, you can have more persistent symptoms that can eventually lead to weakness or disability,” he said.

Here are Dr. Twydell’s tips for preventing that numb or tingling feeling in your extremities:

• Wear wrist splints at night to ease problems with carpal tunnel syndrome.
• Avoid lying on your elbow while sleeping, and try wearing an elbow pad to bed to keep the elbow straight.
• Don’t cross your legs, with one knee draped over the other. That can compress the fibular nerve, which can lead to foot drop, a cause of tripping.
• Avoid the habit of sleeping with your arm stretched out or underneath your partner. Over time this can damage the radial nerve, leading to wrist drop.
• Avoid leaning on your elbows for extended periods. Try adding gel pads to the armrests of chairs, wheelchairs or cars.
• If you do a lot of computer work, use a gel wrist rest. Avoid holding the wrists in either a flexed or an extended position, which can damage the median nerve.
• Eat a well-balanced, low-carb diet. This is especially important for people with diabetes, who are more prone to neuropathies.
• Avoid alcohol in excess, which can cause neuropathy.
• Avoid taking zinc and vitamin B6 in excess, which can cause nerve problems.

Dr. Twydell admits that some of these tips are easier said than done. For example, it’s hard to change the way you sleep, he said. Yet, people who sleep in a way that compresses the ulnar nerve in their elbow “can cause some pretty significant weakness in the hand.”

And if you’re one of those people who rarely experiences numb or prickly limbs, consider yourself lucky. Some people are more prone to nerve compression than others, Dr. Twydell said.

Reprinted with permission from Spectrum Health Beat.